Temperature Phase Transitions in the Perovskite- like Fluoride Crystals S. Krylova1,*, A. Krylov 1, V. Voronov1, A. Oreshonkov1, A. Vtyurin1

1Kirensky Institute of physics SB RAS, Academgorodok 50/38, Krasnoyarsk, 660036, Russia

*Corresponding Author: slanky@iph.krasn.ru The crystalline, ceramic, and film materials with perovskite-like structures A2B(1)B(2)X6 are

widely used as functional elements due to their remarkable properties. Temperature and pressure changes in fluorides [1–4], cause a number of structural phase transitions, which are generally related to changes in the lattice of octahedral groups, such as small pivoting of B(2)X6 octahedra. In particular, these changes manifest themselves experimentally in substantial anomalies in the crystal lattice dynamics, including the condensation of soft phonon modes during displacive transitions. The aim of this paper was to investigate the temperatures phase transitions and determine their mechanisms in this perspective host lattice material by Raman spectroscopy method. Previous investigations of some elpasolites revealed soft mode condensations in low wavenumber region associated with the structural phase transitions.[5, 6] Raman spectra were collected using the polarized radiation of a 514.5nm Ar+ laser (Spectra-Physics Stabilite 2017) power 15mW on the sample in the wavenumber region between 10 and 1200 cm-1.

Figure 1. The correlation diagram of vibrational modes in the elpasolites

As a result of these investigations, we can conclude that structural phase transitions in the

studied crystals are induced by the condensation of soft phonon modes and are not con-nected with the lattice ordering processes. The critical soft mode is associated with the rotations of the octahedral groups and belongs to the low-lying flat phonon branch in the direction Г–Х. According to the results of the spectroscopy of hard high frequency modes the behaviour of the main order parameter is typical for the transitions of the second kind or those of the first kind close to the tricritical point. In the low frequency area, a strong interaction of the fluctuations of the main order parameter with the uncritical hard low frequency modes was found.

References [1] J. M. Dance, J. Grannec, A. Tressaud, M. Moreno, Physica status solidi (b), 173, Issue 2, 579–586 (1992) [2] M. V. Gorev, M.V. Gorev, K.S. Aleksandrov, A. Tressaud, J. Grannec, M. Couzi, Materials Science and Engineering: R: Reports, 24, Issue 3, Pages 81-151 (1998) [3] I. N. Flerov, M. V. Gorev, K. S. Aleksandrov, A. Tressaud and V. D. Fokina, Crystallography Reports, 49, Number 1, 100-107 (2004) [4] A.M. Woods, R.S. Sinkovits, J.C. Charpie, W.L. Huang, R.H. Bartram, A.R. Rossi, Journal of Physics and Chemistry of Solids, 54, Issue 5, 543-552 (1993) [5] A. S. Krylov, A. N. Vtyurin, A. S. Oreshonkov, V. N. Voronov and S. N. Krylova, Journal of Raman spectroscopy, 44, 763-769 (2013) [6] S. N. Krylova, A. N. Vtyurin, A. Bulou, A. S. Krylov, and N. G. Zamkova, Physics of the Solid State, 46, 7, 1311–1319 (2004)

Piezoelectric Enhancement of New Bismuth-based Piezoelectric Materials with Pseudo-cubic Symmetry with and Its Origin Based on Nano/macro Complex-

domain Configurations Satoshi Wada1,*, Ryo Iizuka1, Shintaro Ueno1, Eisuke Magome2, Chikako Moriyoshi2,

and Yoshihiro Kuroiwa2 1 Material Science and Technology, University of Yamanashi, 4-4-37 Takeda, Kofu, Yamanashi

400-8510, JAPAN 2 Department of Physical Science, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima,

Hiroshima 739-8526, JAPAN *Corresponding Author: swada@yamanashi.ac.jp

It is well known that for the relaxor-based ferroelectrics, the domain configuration is

dependent on chemical composition and orientation. This means that if relaxor-based lead-free ferroelectrics are prepared, it can be expected that they might have high piezoelectric performances. Recently, we reported that BaTiO3-Bi(Zn1/2Ti1/2)O3 (BT-BZT) [1] and BT-Bi(Mg1/2Ti1/2)O3 (BT-BMT) [2] were relaxor ferroelectrics with high Tmax (temperature with maximum dielectric constant) over 250 ˚C. Thus, it is possible to control domain configurations by solid solution system between the above relaxors and normal ferroelectric such as BiFeO3 (BF) with high Tc of 830 ˚C. In this study, the BT-BMT-BF and BT-BZT-BF system ceramics were prepared using a conventional solid–state reaction and their crystal structure and electrical properties were investigated [3]. A single phase of perovskite was prepared for these ceramics with various compositions except for a few. TEM observation revealed that BT-BMT had no domain configuration while BF-rich ceramics had normal rhombohedral domain configurations. Moreover, the ceramic with the intermediate composition between relaxor and BF had nanodomain configuration with domain sizes less than 50 nm. For the ceramics, the temperature dependences of dielectric constants were measured at various frequencies, and the Tmax was determined. As the results, the Tmax increased with increasing BF content, while Tmax decreased with increasing BT content. Finally, their strain vs. electric-field behaviors were measured, and the relaxors showed typical electrostrictive behavior while BF-rich ceramics showed typical butterfly-like ferroelectric strain behavior. For the ceramics with nanodomain configuration, the strain curve with hysteresis was clearly observed and the apparent d33

* (= Smax/Emax) from the slope was over 850 pC/N [4].

References [1] C.-C. Huang and D. P. Cann, J. Appl. Phys. 104, 024117 (2008). [2] S. Wada, K. Yamato, P. Pulpan, N. Kumada, B.-Y. Lee, T. Iijima, C. Moriyoshi and Y. Kuroiwa, J. Appl. Phys. 108, 094114 (2010). [3] I. Fujii, R. Mitsui, K. Nakashima, N. Kumada, M. Shimada, T. Watanabe, J. Hayashi, H. Yabuta, M. Kubota, T. Fukui and S. Wada, Jpn. J. Appl. Phys. 50, 09ND07 (2011). [4] I. Fujii, R. Mitsui, K. Nakashima and S. Wada, J. Adv. Dielectrics 4,1450005-1 (2014).

Size Matters: Charge Storage Devices for Inverters Based on Antiferroelectric Ceramics

K. Reichmann*

Institute of Chemistry and Technology of Materials, Graz University of Technology, Stremayrgasse 9, 8010 Graz, Austria

*Corresponding Author: k.reichmann@tugraz.at The demands of power electronics involved in energy conversion in wind or solar power

plants as well as in hybrid cars push the search for new concepts of buffer capacitors as indispensable charge storage devices at high electric fields. Conventional aluminium electrolyte capacitors are limited in switching frequency and operating temperature. Furthermore their volume occupies a great portion of the size of such a converter. Energy efficiency and miniaturization are again strong drivers for technical progress. Therefore components for power electronics have to cope with higher current densities, higher power densities and higher operating temperatures. The increase of switching frequency, which can already be controlled by fast switching SiC- or GaN- power circuits, will provide an appreciable gain in efficiency.

Regarding these requirements antiferroelectric Lead-Lanthanum-Zirconate-Titanate (PLZT) was considered as dielectrics in a new type of multilayer ceramic capacitors. With this material a new device concept has been developed for ripple suppression in high-voltage DC-links of converters and inverters. The multilayer design of these capacitors offers the capability to handle high current levels and a comparably low self-inductance at compact size of the device. The PLZT ceramics provides a maximum of permittivity at a certain electric field combined with a high isolation resistance and an extension in operating temperature.

This presentation highlights the advantages but also the issues of antiferroelectric PLZT ceramics in multilayer ceramic capacitors compared to the standard capacitor solutions and the improvements that have been achieved with this device.

A resource efficient design strategy to optimise the temperature coefficient of capacitance of BaTiO3-based

ceramics. P. Y. Foeller,1,* J. Dean,1 D. C. Sinclair,1 and I. M. Reaney1

1Department of Material Science & Engineering, The University of Sheffield, Sir Robert Hadfield Building, Mappin Street, Sheffield, S1 3JD, United Kingdom

*Corresponding Author: pyfoeller1@sheffield.ac.uk More than 2 trillion units of multilayer ceramic capacitors (MLCC) per annum are required

to meet the demands from the commercial electronic device industry1. This use alone correlates to large quantities of rare earth (RE) oxides required to be used as dopants in MLCC. Especially intermediate sized RE-ions are used to modify the temperature dependence of ferrolelectric BaTiO3 (BT)-based MLCCs to fit industry requirements (e.g. X7R, ± 15 %, -55 to 125 ºC)2,3. As demand for RE oxides threatens to outweigh supply it becomes more important to find suitable replacements.

A novel resource efficient design strategy was implemented to optimise the temperature

coefficient of capacitance (TCC) for BaTiO3-based ceramics without the use of RE-oxides. Instead NaNbO3-doped BT (NNBT) was chosen as it offers a donor+acceptor-dopant system along with readily available starting materials. The experimental strategy is based upon the volume ratio of undoped BT to RE-free NNBT and enables very tight temperature stability control once the optimisation is complete. In addition it offers a faster route than the current techniques based on iterative experimental procedures.

Material1 Material2 Favourable Volume ratio

50 100 1500

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Temperature (qC) Figure 1. Plot showing an optimized Volume ratio of two materials.

The volume ratio that offers the best temperature dependence properties is initially selected

by using an in-house finite element modelling package, which simulates the electrical response of core-shell microstructures of BT-based dielectric materials.4

References [1] J. Ho, T. R. Jow, S. Boggs, IEEE Electr. Insul. Mag., 26, 20-25 (2010) [2] H. Kishi, N. Kohzu, J. Sugino, H. Ohsato, Y. Iguchi, T. Okuda, J. Eur. Ceram. Soc., 19, 1043-1046 (1999) [3] K.-J. Park, C.-H. Kim, Y.-J. Yoon, S.-M. Song, Y.-T. Kim and K.-H. Hur, J. Eur. Ceram. Soc., 29, 1735-1741 (2009) [4] J. S. Dean, P. Y. Foeller, I. M. Reaney, D. C. Sinclair, J. Mater. Chem. A, DOI: 10.1039/C5TA09573E (2016)

Dielectric Nanocomposites for Energy Storage Application Hong Wang

School of Electronic and Information Engineering & State Key Laboratory for Mechanical Behavior of Materials, Xi’an Jiaotong University, Xi’an 710049, China

*Corresponding Author: hwang@xjtu.edu.edu Dielectric capacitors for energy storage have advantages in fast charge-discharge capability

and high power density but their energy densities are at least an order of magnitude lower than that of electrochemical devices, such as batteries and double-layer supercapacitors. Thus the dielectric materials with high energy densities are highly desirable and investigated to reduce the size and cost of electric power system. In this presentation, a brief review of the state of arts on the polymer-based nanocomposites for energy storage applications including our recent highlight works that exhibit excellent energy storage properties will be given. With the studies on filler surface modification, composite structure tailoring and the interface controlling, the dielectric and energy storage properties of the obtained polymer-based nanocomposites have been significantly improved with the optimal combination of high energy density and low dielectric loss. A new kind of advanced material for energy storage capacitors, which exhibits a favorable energy density of 18.8 J cm-3 with the breakdown strength of 470 MV m-1, has been achieved by a novel macro-micro structure design on the composite structure as well as the fillers distribution.

Figure 1. A macro-micro structure designed BT/PVDF nanocomposites with significantly

improved polarization and energy density

References [1] Wang YF, Wang H, et al. Advanced Materials, 27(42), 6657-63 (2015) [2] Niu YJ, Wang H, et al. ACS Applied Materials & Interfaces, 7, 24168-24176 (2015) [3] Niu YJ, Wang H, et al. RSC Advances, 5(79), 64596-64603 (2015) [4] Niu YJ, Wang H, et al. IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency

Control, 62(1), 108-115(2015) [5] Yu K, Wang H, et al. Applied Physics Letters, 104, 082904 (2014) [6] Yu K, Wang H, et al. Applied Physics Letters, 102, 102903 (2013)

Lead-free Anti-ferroelectric Relaxor for Energy Harvesting Applications

Hitesh Borkar, Ashok Kumar * CSIR-National Physical laboratory, New Delhi, India 110012

*Corresponding Author: ashok553@nplindia.org With an increasing demand of electrical energy for powering modern electronic equipments,

a major portion of research is focused on the development for efficient way to produce, storage and distribution of electrical power1. The development of suitable solid state dielectric capacitor with high energy density storage and fast discharge capacity (~ ns) will play a key role in revolutionize modern days electronics and electrical devices. Among popular dielectrics, anti/relaxor ferroelectric (RFE) are strong contender for future ceramic capacitors2. RFE is one of the promising candidates which have enormous potential to utilize in energy storage capacitors and power electronics. To develop a novel RFE, we intentionally modified the morphotropic phase boundary (MPB) composition of (Na0.5Bi0.5)1-xBaxTiO3 (x=0.08) (NBT-BT) with aluminum substitution. The lead-free ferroelectric ceramic [(Na0.42Bi0.44Al0.06Ba0.08)TiO3 (NBAT-BT)] NBAT-BT has been synthesized by conventional solid state reaction route with compositional disorder with four elements (Na/Bi/Al/Ba) positioned at A-site. The positional disorder changes atomic shift of cations which in turns change the functional properties of matrix. Crystal structure was refined by the Rietveld method that confirmed the co-existence of both tetragonal and rhombohedral phases with ratio 52 and 48% respectively. Reliability factors and refinement parameters are in good agreement of d-spacing which observed from lattice resolved high resolution transmission microscopy (HRTEM). Secondary electron microscopy (SEM) shows systematic square grains with average grain size of 1-5 µm with less porosity. Elemental analysis was carried on ceramic pellets which confirm the compositions within the experimental errors of SEM (±5%). Raman spectra confirm the substitution of Al3+ on A-site of crystal structure. Dielectric constant shows a frequency dependent dispersion near 80-110 °C. It also fulfills the basic criteria of relaxor ferroelectric over a wide range of temperatures and frequencies and satisfied the Vogel-Fulcher relation. Diffuse ferroelectric phase transition observed near 230-240 °C and it follows the modified Curie-Weiss law. The large change in ferroelectric phase transition temperature may be due to bismuth deficiencies. Energy density of NBAT-BT was calculated from dielectric constant and polarization-electric field (P-E) loops and found in the range of 0.4-0.6 J/cm3, as shown in Figure1. Temperature dependent I-V characteristic shows a signature of positive temperature coefficient of resistance (PTCR)3. The observed relaxor-antiferroelectric properties may be helpful to design new high constant dielectric devices capable to store high energy density and deliver power instantly. .

-60 -40 -20 0 20 40 60-30

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Figure 1. Temperature dependent P–E hysteresis loop, inset, charging-discharging efficiency, with capacity to storage energy (shaded area) and PTCR behavior.

References [1] S. A. Sherrill, P. Banerjee, G. W. Rubloff and S. B. Lee, Phys. Chem. Chem. Phys., 13, 20714 (2011). [2] Z. M. Dang, J. K. Yuan, S. H. Yao and H. Hong, Adv. Mater., 25, 6334 (2013). [3] H. Borkar, V. N. Singh, B. P. Singh, M. Tomar, V. Gupta, A. Kumar, RSC Advances, 4(44), 22840(2014).

Interesting property studies of SrBi2Ta2O9 and Sr(Bi0.95Sm0.05)2Ta2O9 ferroelectric ceramics fabricated by molten salt flux method

B.Rajesh Kannan and B.Harihara Venkataraman* Department of Physics, Birla Institute of Technology and Science (BITS) - Pilani, Hyderabad

Campus, Jawahar Nagar, Shameerpet Mandal, R. R. Dist - 500078, Hyderabad, India. * Corresponding Author : tut.hari@gmail.com

Abstract Layered ferroelectric materials such as SrBi2Ta2O9 (SBT), BaBi2Nb2O9 (BBN) and Bi4Ti3O12 (BIT) have been proved to be excellent candidates for non- volatile random access memory devices owing to the low fatigue with polarization switching and nontoxicity [1,2]. Nevertheless, these materials exhibit the drawbacks like high processing temperature and low remnant polarization. It is recently found that trivalent rare earth ions doping on the crystal lattice of these layered ferroelectric materials have a significant influence on the physical properties [3]. In this paper, the undoped and 5mol% samarium doped strontium bismuth tantalate [Sr(Bi0.95Sm0.05)2Ta2O9] ceramics have been prepared by the KCl molten salt synthesis route. The X - ray powder diffraction studies have revealed the presence of monophasic perovskite crystalline structure of undoped and samarium doped strontium bismuth tantalate ceramics. The existence of plate shaped morphological features of these ceramics has been demonstrated through scanning electron microscopic studies. It is observed that the dielectric property is superior for samarium doped ceramics than undoped SBT samples. Interestingly, the remnant polarization computed from the hysteresis loop (as depicted in Figure. 1) is higher for samarium doped ceramic samples (Pr = 4.04 PC/cm2) than that of the undoped one (Pr = 0.94 PC/cm2) which may be attributed to the increase in the structural distortion of the perovskite unit in the crystal structure of SBT (Figure. 2). This enhancement could also be induced due to the slight increase in the polar - axis orientation as corroborated by X - ray diffraction studies.

Figure 1. P Vs E hysteresis loops recorded at 300 K Figure 2. Crystal Structure of SrBi2Ta2O9 References [1] T. Sivakumar, M. Itoh, Chem. Mater. 23, 129-131 (2011). [2] A.Z Simões, E.C. Aguiar, C.S. Riccardi, E.Longo, J.A.Varela, B. Mizaikoff, Mater.Chem. Phys. 124, 894-899 (2010). [3] N. Pavlović, V. Koval, J. Dusza, V. Srdi, Ceram. Int. 37, 487- 492 (2011).

Giant dielectric response in composite Ca(Fe,Nb)O3-TiO2 ceramics Y. Zeng,1, 3, * A. A. Bokov,2 D. W. Wang,1 F. Xiang,1 H. Wang1,* and Y. H. Lin3

1 School of Electronic and Information Engineering & State Key Lab for Mechanical Behavior of Materials, Xi’an Jiaotong University, Xi’an, China

2Department, University, Street Address, City, Country Department of Chemistry and 4D LABS, Simon Fraser University, Burnaby, British Columbia, Canada V5A 1A6.

3 School of Materials Science and Engineering, State Key Lab of New Ceramics and Fine Processing, Tsinghua University, Beijing, China

*Corresponding Author: zengyi@mail.tsinghua.edu.cn; hwang@mail.xjtu.edu.cn We report the synthesis and investigation of novel composite ceramics based on perovskite

Ca(Fe1/2Nb1/2)O3 and rutile TiO2. The structure and morphology of the ceramics are studied using x-ray diffraction and scanning electron microscopy; the dielectric spectroscopy is used to study the permittivity in wide ranges of frequency (100~106 Hz) and temperature (90~700K). Large and almost temperature independent static relative permittivity up to 10 5 is observed in a wide range around room temperature in the heterophase 0.5Ca(Fe1/2Nb1/2)O3-0.5TiO2 ceramics composed of perovskite Ca(Fe,Nb,Ti)O3 solid solution and (Ti,Fe,Nb)O2 solid solution with rutile-type structure. The mechanism of this giant dielectric response is found to be extrinsic polarization of the Maxwell-Wagner type. Furthermore, microwave frequency dielectric response is investigated at room temperature and excellent dielectric performance is demonstrated in 0.1Ca(Fe1/2Nb1/2)O3-0.9TiO2.

References [1] P. Lunkenheimer, S. Krohns, S. Riegg, S. G. Ebbinghaus, A. Reller and A. Loidl, Eur. Phys. J. Spec., 180, 61-89 (2010). [2] C. Y. Chung, Y. H. Chang and G. J. Chen, J. Appl. Phys., 96, 6624-6628 (2004). [3] S. Saha and T. P. Sinha, J. Phys. Condens Mat., 14, 249-258 (2002). [4] K. Tezuka, K. Henmi, Y. Hinatsu and N. M. Masaki, J. Solid State Chem., 154, 591-597 (2000). [5] M. Yokosuka, Jpn. J. Appl. Phys., Part 1 34, 5338-5340 (1995). [6] E. L. Colla, I. M. Reaney and N. Setter, Ferroelectr., 133, 217-222 (1992). [7] I. P. Raevski, S. A. Prosandeev, A. S. Bogatin, M. A. Malitskaya and L. Jastrabik, J. Appl. Phys., 93, 4130-4136 (2003). [8] Z. Wang, X. M. Chen, L. Ni and X. Q. Liu, Appl. Phys. Lett., 90, 022904 (2007). [9] Z. Wang, X. M. Chen, L. Ni, Y. Y. Liu and X. Q. Liu, Appl. Phys. Lett., 90 102905 (2007). [10] Y. Y. Liu, X. M. Chen, X. Q. Liu and L. Li, Appl. Phys. Lett., 90, 262904 (2007). [11] Z. Wang and X. M. Chen, Solid State Commun., 151, 708-711 (2011). [12]Z. Abdelkafi, N. Abdelmoula, H. Khemakhem, R. Von der Muhll and L. Bih, J. Alloys Compd., 427, 260-266 (2007). [13] Z. Abdelkafi, N. Abdelmoula, H. Khemakhem, O. Bidault and M. Maglione, J. Appl. Phys., 100, 114111 (2006). [14] S. M. Ke, H. Q. Fan and H. T. Huang, J. Electroceram., 22, 252-256 (2009). [15] A. M. Glazer, Acta Cryst., A31, 756-762 (1975). [16] R. Mani, S. N. Achary, K. R. Chakraborty, S. K. Deshpande, J. E. Joy, A. Nag, J. Gopalakrishnan et al., J. Solid State Chem. 183, 1380-1387 (2010). [17] A. A. Bokov and Y. Zuo-Guang, J. Adv. Dielectr. 2, 1241010 (2012). [18] C. C. Wang, H. B. Lu, K. J. Jin and G. Z. Yang, Mod. Phys. Lett. B 22, 1297-1305 (2008). [19] A. K. Jonscher, Dielectric relaxation in solids. (Chelsea Dielectrics Press, London, 1983).

Electron-pinned defect-dipoles for SrTiO3-based ceramics with high permittivity and low dielectric loss

Nana Wang, Minghe Cao,* Zichen He, Qi Zhang, Hua Hao, Zhonghua Yao, Hanxing Liu

State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Luo Shi Street, Wuhan University of Technology, Wuhan, PR China

*Corresponding author: caominghe@whut.edu.cn (M. Cao) With the rapid development of electronic and microelectronic industry, how to increase the

permittivity and decrease the dielectric loss has been one of the most important research goals in the field of dielectric materials due to their wide applications as energy-storage, capacitors, sensors, memory applications, etc. Many dielectric materials with giant permittivity have been investigated, including BaTiO3-doped perovskites, CCTO, non-ferroelectric transition-metal oxides such as doped NiO, but their dielectric loss is relatively high which cannot be used in practice. So in this paper, we try to prepare a new type material which carrier hopping can be localized by defect states by donor-accepter co-doping [1], leading to both high permittivity and low dielectric loss. SrTiO3 has been taken as the research objects, Nb2O5 and Al2O3 as dopants. This paper is aiming to prepare SrTiO3-based ceramics with high dielectric constant, low dielectric loss and weak temperature- and frequency-dependence.

Sr(Nb0.5Al0.5)xTi1-xO3 (x=0, 0.02, 0.04, 0.06) ceramics were obtained via solid-state reaction method and sintering in air at 1540℃. The grain size of SrTiO3 ceramics decreased with Nb2O5 and Al2O3 doping content. Sr(Nb0.5Al0.5)xTi1-xO3 ceramics exhibit a giant permittivity of about 1.05 × 104 and low dielectric loss of 0.03 measured at room temperature and 1kHz. According to the XRD, XPS, and ac conductivity analysis, this excellent dielectric behaviors of Sr(Nb0.5Al0.5)xTi1-xO3 ceramics would originate the bond[𝑇𝑖4+ ∙ e − 𝑉𝑜∙∙ − 𝑇𝑖4+ ∙ e] [2]，in which the electrons were bound by 𝑇𝑖4+and 𝑉𝑜∙∙ leading to low dielectric loss. In addition, SNAT ceramics were also sintered in oxygen atmosphere and nitrogen atmosphere to verify the existence of [𝑇𝑖4+ ∙ e − 𝑉𝑜∙∙ − 𝑇𝑖4+ ∙ e] . The idea deliberately create local electron-pinned defect-dipoles is a way to make the high-energy-density storage capacitors.

. References [1] W. Hu , Y. Liu , R.L Withers, Nature Materials, 12, 821-826(2013) [2] Z. Wang, M. Cao, Z. Yao, Journal of the American Ceramic Society, 34, 1755-1760 (2014)

Physical properties of Low Temperature Sintering PCW-PNN-PZT Ceramics

for Ultrasonic Sensor

Yong-Jin Kim1, Juhyun Yoo1,* and Ji-Young Lee2

1Department of Electrical Engineering, Semyung University, Jecheon 390-711, Republic of Korea 2Department of Computer Science, Semyung University, Jecheon 390-711, Republic of Korea

1Department of Electrical Engineering, Sinwall Dong, Jechon, Chungbuk, Korea

*Corresponding Author: juhyun57@semyung.ac.kr

In this study, in order to develop the composition ceramics for ultrasonic sensor application,

Pb0.985Bi0.01(Co1/2W1/2)0.03(Ni1/3Nb2/3)0.09(ZrxTi1-x)0.88O3+0.25wt% CuO( abbreviated as PCW-

PNN-PZT) system ceramics were prepared with the variations of x and then their phase

microstructure, piezoelectric and dielectric characteristics were investigated with the variations of

x . The compositions near the morphotropic phase boundary (MPB) appeared when x=0.50.

Moreover, the PCW-PNN-PZT ceramics could be sintered at low temperature of 920℃ and 940℃

by adding sintering aids CuO. At sintering temperature of 920℃ and x=0.50 specimen, the

density(ρ), electromechanical coupling factor(kp), dielectric constant(εr), mechanical quality(Qm)

and piezoelectric constant(d33) piezoelectric figure of merit(d33·g33) indicated the optimal value of

7.94g/cm3. 0.65, 1959, 356, 486pC/N,and 15.56[pm2/N], respectively, suitable for ultrasonic

sensor application. The CuO was proved to lower the sintering temperature of piezoelectric

ceramics due to the effects of PbO and CuO liquid phase.

References

[1] Y. H. Jeong, K. J. Yoo, and J. H. Yoo, J Electroceram, 23 , 387 (2009)

[2] S. Zhang, R. Xia and T. R. Shrout, Materials Science and Engineering B, 129, 131 (2006)

Electrical Properties of (Na,K,Li)(Nb,Sb,Ti)O3 Ceramics for Multilayer-Type Piezoelectric Actuator

Gab-Soo Lee1, Juhyun Yoo1,* , Hyun-Seon Song1 and Sung-Ill Lee3

1Department of Electrical Engineering, Semyung University, Jecheon 390-711, Republic of Korea 2epartment of Safety Engineering, Korea National University of Transportation, Chungju 380-702, Republic of Korea

1Department of Electrical Engineering, Sinwall Dong, Jechon, Chungbuk, Korea

*Corresponding Author: juhyun57@semyung.ac.kr

In this study, lead free CuO added (Na0.525K0.4425Li0.0375)( Nb0.8975Sb0.065Ta0.0375)O3ceramics

and multilayer actuator using the ceramics were fabricated. And then their physical properties

and displacement properties were investigated. The excellent physical properties of

electromechanical coupling factor(kp)=0.4159, piezoelectric constant (d33) =166pC/N and

mechanical quality factor(Qm)=322 were obtained from the 2.5mol% CuO doped

(Na0.525K0.4425Li0.0375)( Nb0.8975Sb0.065Ta0.0375)O3 ceramics sintered at low temperature of 1,000℃

for 3h.

The haptic multilayer piezoelectric actuators were fabricated with LNKNTS + 2.5mol% CuO

ceramics with excellent piezoelectric properties by tape casting methods. The density and

effective electromechanical coupling factor (keff) of manufactured haptic piezoelectric actuator

were 4.4g/cm3 and 0.225, respectively. Total-displacement of central part of the actuator was

increased with increasing input voltage. When input voltage and driving frequency were 20V

and420Hz, the input current, consumption of electrical power and total-displacement were

approximately 324㎂, 5.405㎽ and 36㎛ at non-mass, respectively. Whereas, the electrical

properties such as input current of 358㎂, electrical power consumption of 4.554㎽ and total-

displacement of 18㎛ were decreased at 2.8g mass under 20V and150Hz.

References [1] Y.K.Oh, J.H.Yoo, Mater.Lett.,79,180(2012) [2] J.R.Noh,J.H.Yoo , J.Electroceram, 30,139(2012) [3] M.H.Park,J.H.Yoo, Journal of Elec.Mater.,30,3095(2012)

Electrocaloric Effect of ZnO added 8/65/35 PLZT Ceramics

You Seok Kim1, Jong Dae Han1, Juhyun Yoo1,* , Durk-Won Park2 and Yeong-Ho Jeong3

1Department of Electrical Engineering, Semyung University, Jecheon 390-711, Republic of Korea 2Department of Electrical Engineering, Semyung University, Jecheon 390-711, Republic of Korea 3Department of Safety Engineering, Korea National University of Transportation, Chungju 380-702, Republic of Korea

*Corresponding Author: juhyun57@semyung.ac.kr

In this study, in order to develop low temperature sintering relaxor ferroelectric ceramics for

refrigeration device application with large electrocaloric effect, 8/65/35PLZT ceramics were

manufactured using conventional solid-state reaction method with the amount of ZnO

addition. The XRD pattern of all specimens indicated general perovskite structure with

secondary phase. With increasing the amount of ZnO addition, the coexistence of

rhombohedral and tetragonal phases was observed. From the result of temperature

dependence of dielectric constant, ferroelectric-paraelectric phase transition temperature TC

was shifted toward high temperauture with increasing the amount of ZnO addition,

indicating the relaxor ferroelectric characteristics. The temperature change ⊿T of specimen

exhibited the tendency increasing with the amount of ZnO addition. Furthermore, at the

0.6wt% added ZnO composition ceramics, the optimal value of ⊿T =0.345°C in ambient

temperature of 215°C was appeared. It is considered that 8/65/35PLZTcomposition ceramic

shows the possibility of refrigeration device application.

References [1] Y.S.Kim, J.H.Yoo, Journal of ELECTRONIC MATERIALS, 44,2555 (2015) [2] J. Wang, T. Yang, S. Chen, G. Li, Q. Zhang, and X. Yao,J. Alloys Compd. 550, 561 (2013). [3] J.F. Scott, Science 315, 954 (2007)

Piezoelectric Poly-L-lactic Acid Fabric and its Application to Control of Humanoid Robot

Y. Tajitsu* Faculty of Science and Engineering, Kansai University

3-3-35 Yamate, Suita, Osaka, 564-8680, Japan *Corresponding tajitsu＠kansai-u.ac.jp

At present, the development of breakthrough wearable human-machine interfaces (HMIs)

such as wristwatch and glasses is progressing forward realizing the Internet of Things (IoT). In this study, we report the potential of an application system that enables the monitoring of complex human movements via a type of clothing that can sense complex motion using a piezoelectric poly-L-lactic acid (PLLA) fabric.

We previously reported that a drawn PLLA film exhibits high shear piezoelectricity [1,2]. However, PLLA fibers exhibit piezoelectricity under bending motion but not under stretching motion [1,2]. To solve this problem, we investigated a piezoelectric PLLA fabric using drawn PLLA fibers. Figure 1 shows typical images of the piezoelectric PLLA fabrics, which were produced in plain, twill, and satin weaves. Here, polyethylene terephthalate (PET) and PLLA threads were woven together as the warp and woof, respectively. Carbon fibers with high conductivity were also sewn inside each fabric as

electrodes to detect the piezoelectric response signal. Next, on the basis of the simulation results based on a finite element method (FEM), we designed a smart clothing that can sense its own deformations, such as expansion, bending, and twisting. Actually, this smart clothing consisting of parts with satin, plain, and twill weaves was fabricated using a technique for sewing Japanese kimonos accurately detect the twisting, bending, and elongation motion of the piezoelectric PLLA fabric itself. Finally, a prototype system in which a human was linked to a humanoid robot was developed using the smart clothing. As shown in Fig. 2, pieces of the piezoelectric PLLA fabric were sewn together in both long sleeves of a sweater made of synthetic leather (smart clothing). The piezoelectric response signal generated by the movement of the subject’s arm was processed by analog electrical circuits, including amplifier and filter circuits, and sent to the circuit system controlling the arm motion of the humanoid robot through a wireless communication system. The motion of the human arm could be instantaneously linked to that of the robot arm. At present, simple procedures such as the bending of the arms and the twisting of the wrists can be replicated by the humanoid robot but not complex movements of the arms. Our future aim is for the robot to be able to handle complex movements after increasing the detection accuracy of the piezoelectric PLLA fabric.

We would like to thank Teijin Co., Ltd., for kindly preparing the PLLA fabrics and clothing. This work was also supported in part by Grants-in-Aid for Scientific Research (Nos. 24655108 and 15K13714) from the Ministry of Education, Culture, Sports, Science and Technology of Japan.

References [1] Y. Tajitsu, IEEE Trans. Dielectr. Electr. Insul., vol. 17, pp.1050-1055, 2010. [2] Y. Tajitsu, IEEE Trans. Ultrason. Ferroelectr. Freq. Control, vol. 55, pp.1277-1290, 2008.

Bending of left arm

twill weave

satin weave

plain weave

Figure 1. Piezoelectric PLLA fabric

Figure 2. Prototype system linking motion of human arm to that of a humanoid robot

Growth and observation of multiscale domain morphology of PIN-PMN-PT Ferroelectric crystals

Linghang Wang,1,* Shan Zhao,1 and Fei Li1 1 Electronic Materials Research Lab, Key Laboratory of Ministry of Education and International

Center for Dielectric Research, Xi’an Jiaotong University, Xi’an 710049, P. R. China *Corresponding Author: uswlhcn@yahoo.com

Due to the superior piezoelectric properties compared to polycrystalline ceramics, such as

the ultrahigh piezoelectric coefficients (d33>1500pC/N) and electromechanical coupling factors (k33>90), the ferroelectric perovskite single crystals are regarded as the potential new materials used for electroacoustic, or ultrasonic transduction devices. The ternary Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 (PIN-PMN-PT) crystals were reported to possess improved properties at higher temperature when compared to the binary Pb(Mg1/3Nb2/3)O3-PbTiO3(PMN-PT) crystals, due to the high Curie temperature (~200oC). In this presentation, crystal growth of the ternary PIN-PMN-PT ferroelectric materials was introduced, and the dielectric, piezoelectric, ferroelectric, and optical properties were characterized as well as its electrooptical property. The domain morphology and phase transition of PIN-PMN-PT samples with different thickness at different phase states (R, O, and T) were investigated. The interesting results were obtained that the thinner samples, the narrower transition gaps and the clearer domain morphologies. The peak-like transition boundary was in-situ observed.

Non-destructive Evaluation Technique of Surface Mounted Capacitor based on Photothermal Frequency Modulation Technique

A. Yarai*, and Y. Sato Department of Electronics, Information and Communication Engineering Osaka Sangyo University, 3-1-1 Nakagaito, Daito, Osaka 574-8530 Japan

*Corresponding Author: a.yarai@ieee.org

A surface mounted capacitor (SMC) is one of extremely important passive devices, especially for automatically assembling components onto the electronic circuit board. Incidentally, it is widely known that an applied mechanical stress results a crack on the inside of SMC even through it is a slight magnitude[1]. Accordingly, it is extremely significant for easily diagnosing those with non-destructive. Previously, the evaluation method which uses beams for propagating inside of opaque solids such as infrared, x-ray and ultrasonics have been used in general as the technique for this. They are certain specific advantages, however, each method is not necessarily adequate technique at the production factory mainly due to instrument’s cost and its operability.

This article proposes a new non-destructive evaluation technique for SMC. At first, we describe a principle of our technique, including following features. 1) The thermal wave is generated on the inside of SMC by irradiating a periodical laser beam from the upper surface of SMC. 2) The capacitance is slightly modulated by thermal wave because of a temperature dependence of dielectric constant. 3) Because of this, an oscillation frequency of LC oscillation circuit which is composed of this SMC results a frequency modulation[2]. 4) Finally, the changing of capacitance of SMC 'C could be obtained by FM demodulating the oscillation signal. Here, we believed that the thermal wave is immediately reflected and is dramatically decayed by cutting-off the transmission due to the crack on the inside of SMC, thereby decreasing a changing of capacitance.

Figure 1 shows the modulation frequency fm of laser beam dependence of the changing ratio of capacitance 'C/Co as a function of mechanical stress applied to SMC. Here, a commercially-available SMC (whose the size is 0.8 mm in width, 0.8 mm in depth and 1.6 mm in length, and the capacitance Co is 100 pF, manufactured by Murata Co. Ltd. Japan) was used as the test sample. The power of irradiated laser beam with a wavelength of 806 nm was approximately 0.5 W, and the oscillation circuit mentioned above was designed with the oscillation frequency of 80 MHz. As can be seen in Fig. 1, it is confirmed that 'C/Co is decreased as the applied stress is higher. The reason for this is believed to be diffused and to be expanded the inside crack. It is also demonstrated in Fig. 1 with all test samples that 'C/Co is suppressed as the laser modulation frequency is higher. This is because of a reduction of thermal diffusion length by increasing the modulation frequency. In other words, it is possible to obtain the depth profile of SMC inside by sweeping the modulation frequency. Finally, we believed that our technique is useful for screening a SMC at the manufacturing factory as the first step for the practical application.

Fig. 1. Modulation Frequency of Laser Beam Dependence of Changing Ratio of Capacitance.

References [1] B. Wunderle et al., Proceedings of THERMINIC 2007, p.104 (2007). [2] Y. Cho, T. Kumamura, Rev. Sci. Instrum., 67, 19 (1996).

Effects of Bi2O3 additive on sintering process and dielectric, ferroelectric, and piezoelectric properties of (Ba0.85Ca0.15)(Zr0.1Ti0.9)O3 lead-free piezoceramics

Raziye Hayati1,*, Mohammad Ali Bahrevar1, Touradj Ebadzadeh1, Virginia Rojas2, Nikola Novak2, and Jurij Koruza2

1 Semiconductor Division, Materials and Energy Research Center, 31787/316 Karaj, Iran

2 Institute of Materials Science, Technische Universität Darmstadt, 64287 Darmstadt, Germany

*Email: r-hayati@merc.ac.ir

Abstract

Lead-free Ba0.85Ca0.15Zr0.1Ti0.9O3 (BCZT) piezoceramics with Bi2O3 additive were synthesized using solid-state ceramic processing. Various amounts of Bi2O3 (0.05, 0.1, 0.5, and 1.0 mol%) were added after calcination, milled, compacted, and sintered with no compensation at A- or B-sites. Addition of up to 0.5 mol% Bi2O3 was found to greatly enhance the densification and increase the piezoelectric properties, while higher amounts decreased the grain size and induced relaxor-like electrical behavior, obeying the Vogel-Fulcher model. The highest properties were obtained for the BCZT with 0.1 mol% Bi2O3 sintered at 1350°C: d33=325 pC/m, d33

*=509 pm/V (at 3kV/mm), kp=0.42, and Pr=10.4 µC/cm2. The microstructure, phase composition, and local structure were investigated by scanning electron microscopy, X-ray diffraction, and Raman spectroscopy. The appearance of the A1g vibration mode in the Raman spectra and the shift of diffraction peaks to lower 2θ values indicate the incorporation of Bi3+ into the B-site of the perovskite BCZT structure.

Keywords: Lead free BCZT; Bi2O3addition; Microstructure; piezoelectric; Relaxor.

Simulation and Design of Lead Free Piezoelectric Multilayer Actuator for Haptic Application

Kabsoo Lee1, Juhyun Yoo2,*, Sangho Lee3, Jaeil Hong3 ,Larkhoon Hwang2

1YEMI, 21-28, Palgoe1nonggongdanji-gil, Yeongwol-eup, Yeongwol-gun, Gangwon-do, 26240, Republic of KOREA 21Department of Electrical Engineering, Semyung University, Jecheon 390-711, Republic of Korea

3Department of Electrical Information Control, Dongseoul University, 76, Bokjeong-ro, Sujeong-gu, Seongnam-si, Gyeonggi-do, 13117, Republic of KOREA

*Corresponding Author: juhyun57@semyung.ac.kr

Recently, many mobile devices adopt haptic interfaces for its control and feedback. Haptic

interfaces enable person to communicate with machine through touch and vibration. Haptic interfaces demand low power consumption and precision actuators with rapid response velocity. Piezoelectric actuators can generate variable vibration with low power consumption and have rapid response velocity [1]. It is considered that piezoelectric actuator is one of candidates for prospective haptic interfaces of mobile devices.

Hence, in this study, multilayer piezoelectric actuators were designed and simulated according to SUS316 thickness, actuator width and mass by ATILA software. Numerical modelling based on the finite element method was performed to find the resonant frequencies and modal shapes of the actuator.

Figure 1. Displacement characteristic of each step of multilayer-type piezoelectric actuator

as a function of mass The resonant frequency was affected by the thickness of SUS316 plate and mass. On the

other hand, the width of the actuator did not have a significant impact. Maximum displacements were generated in the center of haptic multilayer piezoelectric actuator. Maximum displacement showed 22㎛ from the piezoelectric actuator without mass.

References [1] I. Poupyrev, S. Maruyama, J. Rekimoto, "Ambient touch: designing tactile interfaces for handheld devices", UIST, p.51-60, 2002.

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Electromechanical coupling in Gd-doped CeO2 studied by laser interferometry A.D. Ushakov1,*, D.O. Alikin1, I.S. Baturin1,

E. Mishuk2, I. Lubomirsky2, V.Ya. Shur1, A.L. Kholkin1,3 1Institute of Natural Sciences, Ural Federal University, Lenina 51, Ekaterinburg, Russia

2Department of Materials and Interfaces, Weizmann Institute of Science, Herzl St 234, Rehovot, Israel

3 Physics Department and CICECO - Aveiro Institute of Materials, University of Aveiro, Aveiro 3810-193, Portugal

*Corresponding Author: bddah@ya.ru Recently Korobko et al [1,2] have shown that thin films of ionic conductors Ce0.8Gd0.2O1.9

(CGO) demonstrate giant electrostriction (and notable piezoelectricity in the biased state) with the electrostriction coefficient in the range 2-10 kPa/(kV/cm2). The ability to generate exceptional strain (> 7 MPa) and absence of lead (together with very stable structure without ferroelectric domains and phase transition) is a great advantage for practical applications such as electromechanical sensors and actuators either ability to work at high temperatures and possible multifunctionality due to notable ionic conductivity.

In this work, we used highly sensitive laser interferometry to probe electromechanical coupling in CGO thin films in the frequency range 2-20 kHz and in film-based membranes in the range 5 Hz – 15 kHz. The measurements were done using a Michelson-Morley interferometer (Fig. 1 a) specially adapted for the registration of small displacements (sensitivity about 0.005 pm at 15 kHz) using lock-in technique and electronic feedback system.

Resulting electrostrictive coefficients of CGO thin films clamped to the substrates are about 10-19 m2/V2 at 13 kHz (2nd harmonic) which is very close to earlier results obtained by cantilever resonator technique [2]. Membranes based on free-standing CGO thin films covered with Al electrodes demonstrated high displacements (≈1.5 nm at 20 Hz with driving voltage 0.7 V) following 1/f-dependence (Fig. 1 b). The results were complemented by measurements of temperature dependences of electrostriction coefficient and spatial distribution across the surface in both thin films and film-based membranes. The mechanism of the giant electrostricition in CGO will be discussed.

(a) (b) Figure 1. (a) Image of the used Michelson-Morley interferometer for the measurements of

small displacements, (b) frequency dependence of the displacements of CGO membrane driven at 0.7 V.

The equipment of the Ural Center for Shared Use “Modern nanotechnology” UrFU was

used. The research was made possible with the financial support of Russian Foundation for Basic Research grant (15-52-06006-MNTI_a).

References [1] R. Korobko et al., Advanced Materials, vol. 24, 5857 (2012) [2] R. Korobko et al., Sensors and Actuators A: Physical, vol. 201, 73 (2013)

Determination of Ferroelectric Order on Electrocaloric Effect in Ferroelectric Ceramics

Yang Bai,1,* Jianting Li,1 Shiqiang Qin,1 Fei Han,1 Lijie Qiao1 1 Institute for Advanced Materials and Technology, University of Science and Technology

Beijing, Beijing, China *Corresponding Author: baiy@mater.ustb.edu.cn

Recently, increased attention has been paid on the electrocaloric effect (ECE) in

ferroelectrics to explore a compact and environmental friendly solid-state cooling technology owing to its advantages of easy miniaturization, high efficiency, and low cost. The ECE refers to a reversible temperature and/or entropy change of a ferroelectric material during the application or removal of applied electric fields, which is a basic characteristic of ferroelectric materials. This presentation focused on the effect of phase transition character on the ECE, and demonstrated the ECE in various perovskite-structure ferroelectric materials.

The first ordered phase transition (FOPT), such as that in BaTiO3, has uniform transition, so that it induces a sharp ΔT peak just above the phase transition point. For example, a giant ECE strength of 0.48K∙cm/kV was observed in a new BT single crystal. In a vicinity of FOPT, the ECE is dominated by the phase transition entropy, which may be two orders of magnitude higher than the dipole order entropy. If the FOPT is diffused gradually by some ion substitutions, such as Sr2+ or Ca2+ in A site and Zr4+ or Sn4+ in B site, the ECE peak turns wider and lower. The inequivalent doping modifies ferroelectric phase transition and corresponding ECE more efficiently. For BaTiO3 with rare-earth elements as donor doping in A site, the ECE increaseingly enhanced with the reduction of rare-earth ionic radius and the samples with Sm, Eu, Gd and Dy dopings exhibit top-level ECE strength within a wide temperature range. In ferroelectric relaxors, such as (BaCa)TiO3-Ba(ZrTi)O3 and Pb(Mg1/3Nb2/3)O3-PbTiO3, the ECE may exhibit an optimized value around the morphortropic phase boundary (MPB), and each ECE peak refers to a certain phase transition. If there are complex transitions between several ferroelectric and/or antiferroelectric phases with different dipole orientations, the ECE may exhibit negative values, such as in Na0.5Bi0.5TiO3 and La doped Pb(ZrTi)O3.

References [1] F. Han, Y. Bai, L. J. Qiao, et al, Journal Materials Chemistry C, 4, 1842 (2016) [2] Y. Bai, D. Wei, L. J. Qiao, Applied Physics Letters, 107, 192904 (2015) [3] Y. Bai, X. Han, L. J, Qiao, RSC Advances, 5, 71873 (2015) [4] X. C. Ren, W. L. Nie, Y. Bai, et al, The European Physical Journal B, 88, 232 (2015) [5] Y. Bai, X. Han, X. C. Zheng, et al, Scientific Reports, 3: 2895 (2013) [6] Y. Bai, X. Han, K. Ding, et al, Applied Physics Letters, 103: 162902 (2013) [7] Y. Bai, X. Han, L. J. Qiao, Applied Physics Letters, 102: 252904 (2013) [8] Y. Bai, K. Ding, G. P. Zheng, et al, AIP Advances, 2, 022162 (2012). [9] Y. Bai, K. Ding, G. P. Zheng, et al, Phys Status Solidi A, 209, 941 (2012) [10] Y. Bai, G. P. Zheng, K. Ding, et al, Journal of Applied Physics, 110, 094103 (2011) [11] Y. Bai, G. P. Zheng, S. Q. Shi, Materials Research Bulletin, 46, 1866 (2011) [12] Y. Bai, G. P. Zheng, S. Q. Shi, Applied Physics Letters, 96, 192902 (2010) [13] Y. Bai, G. P. Zheng, S. Q. Shi, Journal of Applied Physics, 108, 104102 (2010)

Tetragonal High-Tc Mn:PIMNT Pyroelectric Single Crystals for High Detectivity Infrared Sensor Applications

X. Y. Zhao,1,* L.R. Yang,1 H.S. Luo,1 Q. Xu1, and L. Li1

1 Shanghai Institute of Ceramics, Chinese Academy of Sciences, 215 Chengbei Road, Jiading District, Shanghai 201800, China

*Corresponding Author: xyzhao@mail.sic.ac.cn

Pyroelectric materials have important applications in uncooled infrared detection area, such

as gas sensors, flame detectors and thermal cameras. It has been found that relaxor-based ferroelectric single crystals of Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMNT) family have high pyroelectric coefficients and figures of merit for detectivity to be used in novel high-performance infrared sensors with very high specific detectivity. But the disadvantages of PMNT are the lower Curie temperature (about 130 oC). In this study, high Curie temperature (Tc) and Mn ion doped Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 (Mn:PIMNT) single crystals have been grown using modified Bridgman method with compositions corresponding to the tetragonal phase at room temperature.

Figure 1. As prepared Mn:PIMNT pyroelectric single crystals

Fig. 1 (a) shows as grown Mn:PIMNT single crystals with the diameter larger than 2 inches.

The tetragonal phase Mn:PIMNT single crystal has also high pyroelectric coefficient of about 7×10−4 C/m2 K and very low dielectric loss of 0.05%. The tetragonal Mn:PIMNT single crystal has a high Curie temperature (Tc) of higher than 210 oC for special compositions. The Mn:PIMNT pyroelectric single crystals have been thinned to below 20 micrometers and poled to process the infrared sensitive element with size of 2 mm × 2 mm. After integrating the infrared absorptive layer, low noise electric circuit, and TO packaging, voltage mode infrared sensors have been fabricated using the as prepared pyroelectric elements. The voltage mode Mn:PIMNT sensor has higher specific detectivity (D*) of 1.18×109 cm(Hz)1/2/W. Due to the higher Tc of Mn:PIMNT single crystal, the Mn:PIMNT infrared sensors have also the merit of very high processing and service temperature of higher than 200 oC. The research demonstrates the great application potential of tetragonal Mn:PIMNT single crystals in uncooled infrared detecting technology, such as high precision NDIR gas sensing.

References [1] L. Li, et al., Advanced Materials, 26, 2580-2585 (2014). [2] A. Movchikova, et al., AMA Conferences 2013 - SENSOR 2013, OPTO 2013, IRS 2 2013, 16- 19 (2013).

Modeling dielectric polymers behavior in Time Domain A. Soualmia,1,* M. Abdelguerfi,1 and C. A. Gherbi1

1 USTHB , Faculté de Physique , BP 32 , Alger, Algeria *Corresponding Author: a_soualmia@yahoo.fr

Dielectric properties study of polymers concerns primarily with the relationship between the external measured macroscopic quantities such as dielectric permittivity, electrical conductivity and the molecular and atomic structure of the dielectric material [1] Molecular motions and dielectric relaxation process can be studied over a wide frequency range when an electromagnetic field is applied to dielectric materials leading to observed responses which can be related to molecular events caused by dipole orientation and charge migration [2] Migration of charges gives rise to dielectric losses by conductivity and dipole orientation produced as a result of the dipole alignment in the applied field direction gives rise to dielectric losses by relaxation process.

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time (ns) Figure 1. TDR waveforms in matched end-line Figure 2. TDR principle

Basically, behaviour of polar and conductive molecules is experimentally described by the conductivity and dielectric permittivity over the necessary frequency range [3]. But because the whole field of dielectric spectroscopy covers an unusually wide frequency range, a large number of tools and laborious frequency domain techniques may then be required [4],[5],[6] This is why the most attractive aspect of dielectric spectroscopy lies in its applicability to the study of direct correlations between the response of real system that is the Sample Under Test (SUT) and an idealized equivalent electrical model circuit of discrete components as resistances, capacitances[7] Fig.1 is experimental example of polymers with high polar molecules and different electrical conductivity (de-ionized water and salt) by Time Domain Reflectometry (TDR) principle shown in Fig.2 References [1] Debye, P. 1929. “Polar molecules”. Dover, Mineola, New York. [2] N. Asaka, N Shinyashiki, T. Umehara, S. Mashimo“Dielectric Dispersion of primary alcohols in polymer complex" J. Chem. Phys.93 (11) 1 December 1990 8273. [3] Huisman, J.A., Lin, C.P., Weihermüller, L., Vereecken, H., 2008. “Accuracy of bulk electrical conductivity measurements with tdr measurements” Vadose Zone Journal 7, 426–433 [4] Huisman, J.A. 2002. “Comparison of travel time analysis and inverse modeling for soil water content determination with time domain reflectometry”. Water Resour. [5] Lin, C.P., Chung, C.C., Tang, S.H., 2007. “Accurate TRD measurement of electrical conductivity Soil Science Society of America Journal 71, 1278–1287New York: Oxford University Press. [6] R. H. Cole, J. G. Berberian, S. Mashimo, G. Chrssikos, A. Burns, and E. Tombari, "Time domain reflection methods for dielectric measurements to 10 GHz" J. Appl. Phys 66, 793 (1989). [6] Wickens, Thomas D., (2002) “Elementary Signal Detection Theory”

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Fabrication and characterization of c-axis oriented hydroxyapatite thin film Keishiro Hirata,1 Shinji Takayanagi,2 Mami Matsukawa1,*

1Department of Electrical and Electronic Engineering, Doshisha University, 1-3, Miyakodani, Tatara, Kyotanabe-shi, Kyoto, Japan

2Graduate School of Mechanical Engineering, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya-shi, Aichi, Japan

*Corresponding Author: mmatsuka@mail.doshisha.ac.jp Hydroxyapatite [HAp, Ca10(PO4)6(OH)2] is one of the main components of bone and

typically used as the coating of metal implants [1]. Small piezoelectric effect of HAp was reported in the past [2]. In addition, a range of piezoelectric bioceramics has been shown to be biocompatible. The improved bone ingrowth has also appeared around these materials in cases the material was appropriately loaded [3]. In this study, we tried to observe the piezoelectric strain of uniaxial oriented HAp.

We fabricated c-axis oriented HAp thin film by RF magnetron sputtering. We used the Ca10(PO4)6(OH)2 target (Kojundo Chemical Laboratory) for the sputtering. Thin HAp film was deposited on an Al-coated silica glass substrate (25×75×0.5 mm3) without the epitaxial effects. The pressure of atmospheric gas (Ar) was kept at 0.40 Pa during sputtering. The RF power at 13.56 MHz was 100 W, which was supplied by the high frequency power source (ULVAC, RFS-02CA). The discharge was retained for 14 hours without substrate heating. The film thickness of the obtained film sample was 1.6 μm.

We have then evaluated the crystalline orientation of the film by X-Ray diffractometer (PANalytical, X-pert Pro MRD). We also measured the piezoelectric strain of the film by piezoresponse force microscopy (Nanocute, SII Nanotechnology).

Fig. 1 shows the XRD pattern of a sample. A peak of HAp (002) plane was the strongest, telling that c-axis of crystal aligns perpendicular to the substrate. Fig. 2 shows the pole figure of the sample. Full-width at a half maximum of (002) plane was 20º.

Fig. 3 shows the 2D polarization mapping of the film sample. Applied AC voltage was 1.0 Vp-p and 5.0 kHz. Compared with piezoelectric materials, relatively weak strain appeared at each micro-order grain [4]. This result indicates small piezoelectric effect of HAp crystals. References [1] W. Suchanek et al, Journal of Materials Research, vol.13, pp.94-117(1998) [2] S. B. Lang et al., Applied Physics Letters, vol.98 art. no.123703(2011) [3] F. R. Baxter et al., Annals of Biomedical Engineering, vol.38, pp.2079-92(2010) [4] H. Maiwa et al., Ferroelectrics, vol.475, pp.71-81(2015)

Figure 1 XRD pattern of the HAp film sample.

Figure 2 pole figure of the HAp film sample.

Figure 3 PRM image of HAp film sample.

A phase-field model on relaxor ferroelectrics based on random field theory Shuai Wang,1,2* and Bai-Xiang Xu1

1Mechanics of Functional Materials, Technische Universität Darmstadt, Jovanka-Bontschits-Straße 2, Darmstadt, Germany

2Graduate School of Computational Engineering, Technische Universität Darmstadt, Dolivostraße 15, Darmstadt, Germany

*Corresponding Author: wang@mfm.tu-darmstadt.de Relaxor ferroelectrics are a class of disordered crystals with very high piezoelectric effect.

In order to reveal its unique physical origins and to explore its application potential, a lot of investigations have been carried out both theoretically and experimentally. Although there is plenty of work on phase field modeling of conventional ferroelectrics, phase field simulations on relaxor ferroelectrics are scarce in the literature, due to the complex physical origins of relaxor features.

Figure 1. Equilibrium domain configuration for three cases with different Gaussian distribution variances: (a) Δ=0 kV/mm; (b) Δ=3 kV/mm; (c) Δ=8 kV/mm. Four colors represent four polarization orientations of domains.

Based on previous work on ferroelectrics, the authors present in this work a phase-field

model for relaxor ferroelectrics based on random field theory. Spontaneous polarization is chosen as the order parameter. The random field obeys the Gaussian distribution and its strength can be modified by the parameter Δ, the variance of the distribution. Finite element simulations based on this model demonstrate that the model can reproduce relaxor features, such as domain miniaturization (Fig. 1), small remnant polarization and large piezoelectric response. Different simulation cases including relaxation process, bipolar loading, pure mechanical loading and electro-mechanical loading shows the capability of the model. Simulation results show that the domain size becomes smaller as the random field becomes stronger in relaxation process, which is in consistent with experimental characterization. Under pure electric loading, the remnant polarization and coercive field becomes smaller as the random field becomes stronger. The remnant polarization decreases with the increase of random fields. When bipolar loading is applied on a preloaded sample, the macroscopic properties such as remnant and maximum polarization can be modified. For instance, the sample with lower random field have smaller remnant polarization, while the sample with higher random field have smaller maximum polarization under compression loading.

The work of Shuai Wang is supported by the 'Excellence Initiative' of the German Federal and State

Governments and the Graduate School of Computational Engineering at Technische Universität Darmstadt

References [1] A.A. Bokov, and Z-G. Ye. "Recent progress in relaxor ferroelectrics with perovskite structure." Frontiers of Ferroelectricity. Springer, 31-52 (2006). [2] S. Wang, M. Yi and B.-X. Xu, International Journal of Solids and Structures, vol 83, 142-153 (2016)

BCZT as an electrocaloric (pyroelectric) material for future solid state cooling systems

Hojat Pooladvand1,*, Carl Meggs1, Rex Harris1, Vijay Bijalwan2, Yang Bai2, Hana Hughes2 and Tim Button1,2

1 School of Metallurgy and Materials, University of Birmingham, UK

2 Central European Institute of Science and Technology (CEITEC), Brno, Czech Republic

*Corresponding Author: hxp395@bham.ac.uk

Cooling systems based on the compression of gases such as Freon are ubiquitous but

potentially suffer from environment problems. Therefore research is focussing on the

development of alternative cooling technologies. One of the newest methods is concerned

with the use of electrocaloric materials to make a cooling system, in addition to other energy

harvesting applications. The electrocaloric effect (ECE) is the reverse of the pyroelectricity,

and is the ability of some dielectric materials to change their temperature under the

application of an applied electric field. When such materials are cycled in adiabatic and

isothermal conditions, they can be used as the basis of a cooling system. In this paper we

report an investigation of the ECE effect in the lead-free ferroelectric Ba0.85Ca0.15Ti0.9Zr0.1O3

(BCZT). Bulk BCZT ceramics have been prepared by a solid – state method and sintered at a

range of temperatures from 1400-1500℃. The influence of sintering temperature on the

relative density, relative permittivity, d33, grain size and kp has been determined. The

electrocaloric effect has been measured by both direct and indirect methods. A device for

direct measurement of ECE was designed and fabricated, and the results compared to those

obtained from indirect measurements derived using the Maxwell relation on polarization –

electric field data. The optimum properties have been observed for samples sintered at

1450℃.

The control of switchable photovoltaic response in BiFeO3 based ferroelectric thin films

Linxing Zhang, Jun Chen,* and Xianran Xing

Department of Physical Chemistry, University of Science and Technology Beijing, Beijing 100083, China

*Corresponding Author: junchen@ustb.edu.cn To settle the growing energy crisis and environmental issues, photovoltaic, as the clean and

renewable solar energy, based on ferroelectric oxides has recently got renewed attention owing to many unique advantages, such as the switchable photocurrent and photovoltage, and the above bandgap open circuit voltages. Ferroelectric photovoltaic (FEPV) effect has attracted widespread attention due to its special potential for energy conversion, optoelectronics, and information storage.[1,2] In contrast to the known photovoltaic effect of conventional p-n junction interfacial solar cells with the narrow separated area, the photoexcited carriers in FEPV effect are transported by the polarization-induced internal electric field, which is also called the depolarization electric field. The field is generally believed to occur throughout the entire ferroelectric material, resulted in the bulk effect of FEPV. In principle, it implies the energy conversion efficiencies of FEPV can reach higher than the maximum value (∼34%) reported in traditional silicon-based bipolar heterojunction solar cells. However, due the low conductivity of ferroelectric materials, until recently, the FEPV effect remained a scientific curiosity with very poor power conversion efficiency values in devices. Hence, the research of FEPV would take much effort.

Herein, the ferroelectric BiFeO3-based thin films fabricated by a simply chemical solution growth exhibit well ferroelectric properties with little lanthanide substitution. Switchable ferroelectric photovoltaic response shows stable switching and good retention properties.[3] The standard hysteretic loop of photoresponse signal directly indicates hysteretic modulation of photovoltaic by ferroelectric polarization. Intriguingly, the switchable photovoltaic response could be regularly controlled by the polarization, oxygen vacancies and interface barrier in BiFeO3 based ferroelectric thin films.

Figure 1. P-V characteristics of BiFeO3 based films. Figure 2. The control of FEPV effect.

Reference [1] R. Nechache, C. Harnagea, S. Li, et al. Nat. Photonics, 9, 61-7 (2015).

[2] R. Guo, L. You, Y. Zhou, et al. Nat. Commun., 4, 1990, 5pp (2013).

[3] L. X. Zhang, J. Chen, J. Cao, et al. J. Mater. Chem. C, 3, 4706-4712 (2015).

Bridgman Growth of <001>-Oriented φ4in PIN-PMN-PT Piezoelectric Crystals J. Luo, S. Taylor and W. Hackenberger

TRS Technologies, Inc, 2820 East College Ave, State College, PA 16801, USA *Corresponding Author: jun@trstechnologies.com

Single crystal relaxor-based ferroelectrics, relaxor-PbTiO3 (relaxor-PT), possess extremely

high electromechanical coupling coefficient, piezoelectric coefficient, dielectric permittivity and elastic compliance[1], so they became a family of materials excellent for broadband, high sensitivity medical ultrasound imaging transducers, naval underwater sonar transducers and non-destructive evaluation (NDE) transducers[2]. A broad range of sensors and actuators are potential applications for these crystals as well[2].

Sponsored by Office of Naval Research (ONR) through a STTR phase I program, TRS Technologies, Inc. developed Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 (PIN-PMN-PT) single crystals by the Bridgman method in 2007, which extended upper end of the operational temperature by more than 30°C and doubled the operational bipolar electric field in comparison to Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT) single crystals[3]. Recently, the Bridgman process for 4in diameter, <001>-oriented PIN-PMN-PT crystal growth has been established at TRS. The crystals harvested are free of inclusions/voids or other macro defects. The measured property distribution along the crystal growth direction and the property uniformity within (001) wafers are comparable to those of the 3in diameter PIN-PMN-PT crystals commercially produced at TRS. Fabrication of large sizes (>50mm in length), ultra thin (~50um in thickness) crystal plates for medical ultrasound transducers has been demonstrated.

Figure 1. An as-grown 4in diameter <001>-oriented PIN-PMN-PT crystal boule

References [1] S.E. Park, T.R. Shrout, J. Appl. Phys. 82, 1804–1811 (1997) [2] S. Zhang, F. Li, X. Jiang, J. Kim, J. Luo, X. Geng, Progress in Materials Science, 68, 1–66 (2015) [3] J. Luo, W. Hackenberger, S. Zhang, T.R. Shrout, IEEE International Ultrasonics Symposium Proceedings, Beijing, China, 2–5 November (2008)

Elastic Constants in Pb(Mg1/3Nb2/3)O3-PbTiO3 Single Crystals and Ceramics Evaluated by Sound Velocities

Toshio Ogawa* Department of Electrical and Electronic Engineering, Shizuoka Institute of Science and

Technology, 2200-2 Toyosawa, Fukuroi, Japan *Corresponding Author: ogawa@ee.sist.ac.jp

Sound velocities were measured in relaxor single-crystal plates (21 mmL, 14 mmW, 0.4

mmT) of (100)0.70Pb(Mg1/3Nb2/3)TiO3-0.30PbTiO3 (PMNT70/30) and piezoelectric ceramic disks (dimensions of 14-20 mmφ, 0.5-1.5 mmT) composed of PZT, lead titanate, PMNT70/30 and lead-free using an ultrasonic precision thickness gauge (Olympus Model 35DL) with high-frequency (longitudinal wave: 30 MHz and transverse wave: 20 MHz) pulse generation [1]. Directions of DC poling and sound wave propagation are in thickness. Estimating the difference in the sound velocities [longitudinal (VL) and transverse waves (VS)] and elastic constants in the single crystals and ceramics, it was possible to evaluate effects of domain and grain boundaries on elastic constants. Piezoelectric ceramics with high coupling factor were realized in small Young’s modulus (Y) and rigidity (G), and large Poisson’s ratio (σ) and bulk modulus (K) [1]. In PMNT70/30 single-crystal plates, they possessed relatively small σ (0.0 before poling and 0.16 after poling) and K (3.71 and 7.82×1010 N/m2) in comparison with the ones of PMNT70/30 ceramics (σ=0.36 and 0.40/ K=10.1 and 12.1×1010 N/m2) as shown in Table 1. The existence of domain boundaries in single-crystal plates caused decreasing Y, G, σ and K. The existence of grain boundaries in PMNT70/30 ceramics caused decreasing VS (-1,000m/s), as the result, Y and G become smaller and σ and K become larger in comparison with the ones in the single-crystal plates (Table 1). The effects of introducing domain and grain boundaries on elastic constants act like same for Y and G. It was though that domain and grain boundaries function as absorption of mechanical stress because of introducing defects accompanied with the boundaries. Furthermore, the different origin regarding the crystal alignment of piezoelectricity between single crystal (domain alignment) and ceramics (grain alignment) was suggested from the viewpoints of the elastic constants.

Material Elastic constants

Density (g/cm3)

VL

(m/s) V

S/L

(m/s) V

S/W

(m/s) Y

L Y

W

(×1010 N/m2) Single crystal

Av. 8.10 4,565 2,897 2,895 15.8 15.8 σ 0.01 12 41 32 0.2 0.2

Ceramics Av. 7.89 4,466 1,862 7.61 σ 0.02 12 12 0.09

Material Elastic constants

σL σ

W

(─) G

L G

W

(×1010 N/m2) K

L K

W

(×1010 N/m2) Single crystal

Av. 0.16 0.16 6.80 6.79 7.82 7.82 σ 0.01 0.01 0.19 0.15 0.19 0.14

Ceramics Av. 0.395 2.73 12.1 σ 0.002 0.03 0.01

Acknowledgments: This work was partially supported by Grants-in-Aid for Scientific Research C (Nos. 21560340 and 26420282) from the Ministry of Education, Culture, Sports, Science and Technology, Japan, and a Cooperation Research Foundation 2014-2015 between Academy and Industry of Fukuroi City, Shizuoka, Japan. Reference [1] T. Ogawa, in Ferroelectric materials - Synthesis and characterization, ed. AP. Barranco, pp. 33-58 (InTech, Rijeka, 2015).

PMNT70/30 single-crystal plate, n=6 pcs. PMNT70/30 ceramic disk (20.0 mmφ, 1.00 mmT), n=10 pcs. Subscripts of L and W mean values in length and width directions on single-crystal plate.

Table 1 Elastic constants in PMNT70/30 single-crystal plates and ceramics after DC poling.

Significantly Enhanced Breakdown Strength and Energy Storage Density in Sandwich-structured BaTiO3/Poly (vinylidene fluoride) Nanocomposites

Y. Wang,1,* J. Cui,1 Q. Yuan,1 Y. Niu,1 Y. Bai,1 and H. Wang1 1 State Key Laboratory for Mechanical Behavior of Materials, Xi’an Jiaotong University, No.28,

Xianning West Road, Xi'an, China *Corresponding Author: wangyfxjtu@163.com

With the rapid development of electric industry, there are great needs for advanced electric

energy-storage systems, and thus for innovative energy-storage materials. Compared with other electrical energy-storage devices, dielectric capacitors have advantages in fast charge–discharge capability and high power density. While their energy densities are at least an order of magnitude lower than that of electrochemical devices. Consequently, polymer-based dielectric materials with high energy densities are highly desirable and have been investigated to reduce the size and cost of electric power system.

In this study, a kind of sandwich-structured poly (vinylidene fluoride) (PVDF) based nanocomposites were fabricated by solution casting method layer by layer, in which the BaTiO3 (BT) nanoparticles with high dielectric permittivity were introduced into PVDF matrix as the fillers. In this particular topological structure, different layers played different roles when BT/PVDF nanocomposties were applied under high electric field as energy storage capacitors, and both of high breakdown strength and large dielectric polarization could be achieved simultaneously. Besides, finite element simulation method was adopted to analyze the electric field distribution in this sandwich nanocomposites, which can be well adjusted as a result of the difference between the dielectric constant of PVDF matrix and that of BT fillers. A strong interfacial barrier effect can be observed in the simulation result, which is the most significant reason for blocking electrical tree and enhancing dielectric breakdown strength. As a result, the energy storage density of 18.8J/cm3 can be achieved with the breakdown strength of 470MV/m, which is more than three times larger than that of pure PVDF films and five times than that of commercial BOPP. The results indicate that the energy storage of ceramic/polymer composites can be improved further through structural design.

Figure 1. Electric field dependent energy density of sandwich BT/PVDF nanocomposites

(“20-1-20,” with 20 vol% BT in “soft layers” and 1 vol% in “hard layer”), single-layer BT/PVDF nanocomposites (“1,” with 1 vol% BT), and pure PVDF.

References [1] B. Chu, et al., Science, 313, 334 (2006) [2] P.H. Hu, et al., Adv. Funct. Mater., 24, 3172 (2014) [3] Y. Wang et al., Adv. Mater., 27, 6658 (2015)

Large Stroke High Fidelity PZN-PT Single Crystal “Stake” Actuator Yu Huang1,2*, Yue Xue Xia2, Dian Hua Lin2, Kui Yao3 and Leong Chew Lim2

1Department of Mechanical Engineering, National University of Singapore, 21 Lower Kent Ridge Road, Singapore 119077 2Microfine Material Technology, 10 Bukit Batok Crescent, The Spire # 06-02, Singapore 658079 3Institute of Materials Research and Engineering (IMRE), A*STAR (Agency for Science, Technology and Research), #08-03, 2 Fusionopolis Way, Innovis, Singapore 138634

*Corresponding Author: huangyu@nus.edu.sg

A new piezoelectric actuator design, called “Stake” actuator [1], is investigated in this work.

In the example presented, the “stake” actuator is made of four d32–mode PZN-5.5%PT single crystals bonded with the aid of polycarbonate edge guide-cum-stiffeners into a square-pipe configuration, for improved bending and twisting strengths. Said stake configuration averts the non-uniform axial and radial strains as in a machined-single crystal ring, thus achieving high and uniform axial displacement as a result. It is also cost effective to produce as vast material wastage resulting from cutting out a similar actuator from a solid block of crystal is avoided. The displacement-voltage responses, blocking forces, resonance characteristics of the fabricated actuator samples, as well as the load and temperature effects, are measured and discussed. Due to the negative d32 value, this actuator contracts instead during unipolar drive. Bias drives are recommended when extension of the actuator is desired during application. Size for size, the single crystal d32 stake actuators display about 50% larger stroke with intermediate blocking force as oppose to state-of-the-art PZT stacked actuators. Despite its small dimensions of 5x5 mm2 in footprint and 28 mm in height, this single crystal stake actuator has negligible hysteresis even at a stroke of up to 37 µm (Fig. 1). PZN-PT single crystal stake actuators thus provide potential solution to open loop control of the system and reduces heat generation in high power application.

Figure 1. Displacement-electric field response under nil bias drive shows negligible hysteresis even at a stroke of up to 37 µm. The stake actuator measures 5x5 mm2 in footprint and 28 mm in height. References [1]: Y.X. Xia, Nelly Goh, D.H. Lin, “Cost-effective single crystal multi-stake actuator and method of manufacture,” WIPO/PAT No. 2013/100860 A1, July 4, 2013.

Ruddlesden–Popper Perovskite sulfides A3B2S7: A new family of ferroelectric photovoltaic materials for the visible spectrum

Gaoyang Gou1,* and Ju Li2,* 1Frontier Institute of Science and Technology, Xi'an Jiaotong University, Xi'an 710049,

People's Republic of China 2Department of Nuclear Science and Engineering, Massachusetts Institute of Technology,

Cambridge, MA 02139, United States *Corresponding Author: gougaoyang@mail.xjtu.edu.cn, liju@mit.edu

Perovskite ferroelectric materials exhibit the novel ferroelectric photovoltaic effect, where

photon-excited electron–hole pairs can be separated by ferroelectric polarization. Especially, semiconducting ferroelectric materials with small band gaps (Eg) have been extensively studied for applications in solar energy conversion. Traditional route for creating semiconducting ferroelectrics requires cation doping, where Eg of the insulating perovskite ferroelectric oxides are reduced via substitution of certain cations.[1,2] But cation doping tends to reduce the carrier mobility due to the scattering, and usually lead to poor photovoltaic efficiency. In the present work, based on first-principles calculations, we propose and demonstrate a new strategy for designing stoichiometric semiconducting perovskite ferroelectric materials. Specifically, we choose the parent non-polar semiconducting perovskite sulfides ABS3 with Pnma symmetry, and turn them into ferroelectric Ruddlesden–Popper A3B2S7 perovskites with spontaneous polarizations. Our predicted Ruddlesden–Popper Ca3Zr2S7 and other derived compounds exhibit the room-temperature stable ferroelectricity, small band gaps (Eg < 2.2 ) eV suitable for the absorption of visible light, and large visible-light absorption coefficient exceeding that of Si.[3]

Figure 1. Crystal structure for Ruddlesden–Popper Ca3Zr2S7, cation displacements are

shown by arrows. Based on our calculation, Ca3Zr2S7 is a direct band gap semiconductor (Eg = 2.1 eV), exhibiting the visible light absorption coefficient larger than bulk Si.

References [1] Gaoyang Gou, Joseph W. Bennett, Hiroyuki Takenaka, Andrew M. Rappe, Phys. Rev. B, 83, 205115 (2011) [2] Ilya Grinberg, D. Vincent West, Maria Torres, Gaoyang Gou, David M. Stein, Liyan Wu, Guannan Chen, Eric M. Gallo, Andrew R. Akbashev, Peter K. Davies, Jonathan E. Spanier and Andrew M. Rappe, Nature, 503, 509 (2013) [3] Hua Wang, Gaoyang Gou*, Ju Li*, Nano Energy, 22 507-513 (2016)

Research on A Trans-scale Inertial Stick-Slip Platform Driven by Piezoelectric Ceramics

Bowen ZHONG1, Zongwei LI1, Zhenhua WANG1,*, Lining SUN1, Linsen CHEN2 1The College of Mechanical and electrical engineering & Collaborative Innovation Center of

Suzhou Nano Science and Technology, Soochow University, Suzhou, China 2SIP Postdoctor Station of SVG Digitoptics, Suzhou, China

*Corresponding Author:1215537405@qq.com Abstract—The inertial stick-slip platforms driven by piezoelectric ceramics have

comprehensively application in the field of nanomanipulation and nanoassemblies field. In this paper, our investigation is mainly focused on designing and manufacturing a novel structure of inertial stick-slip platform. There are some advantages that higher integration and consistency of every step, more easily changing the friction in fine adjustment, etc. To describe the inertial stick-slip phenomenon exhaustively, the LuGre friction model has been taken into account in the kinetics model. Intuitively, the whole movement of the inertial stick-slip system has been simulated by Matlab, and the result consists of curve of displacement. The prototype has been done some experiments, and the displacement of the inertial stick-slip driving stage has been taken down. Lastly, we compare the curve of displacement and velocity tested by Polytec Laser Vibrometer with the simulation result to verify the accuracy of the kinetics model.

Fig. 1. The simplified engineering model of inertial stick-slip driving system

The inertial stick-slip system can be simplified as Fig. 1. The kinetics model consists of the electrical model of PZT and the LuGre friction model, the mathematical equation can be obtained in its reduced form in Equation（1）.

2

20

0 1 2 2 2 2 1( / )

21 2

( )

33

( )( )

( )

{ [1 ]}

spx v

c s c

tRC

eff p p p p p p

z x z x x m xf f f e

xm m

m x c x k x k n d V e

G

VV V Vª º�¬ ¼

�

­ ª º° « »� � � � �° « »� �° ¬ ¼ ®

�°°° � � � � � u �¯

（1）

The direction of the movement

The cross roller guide

Adjusting screwSpacer

Piezoelectric Ceramics

Flexible structureleaf spring

Adjusting screw

Adjusting screw

-2 -1 0 1 2 3 4 5 6x 10-3

-0.5

0

0.5

1

1.5

2

2.5 x 10-5

Time（s）

Dis

plac

emen

t(m)

testing resultsimulation result

Fig. 2 A novel inertial stick-slip driving prototype Fig. 3 The testing result and simulation result

In detail, the structure of the new prototype has been introduced, as seen in Fig.2. The size of stage is 25×28×30mm and some properties has been tested: The movement range is 20mm, the maximum velocity is 14mm/s, the holding force is 3.8N and the pull force is 1.5N. The red imaginary line is the simulation result and the blue solid line is the testing result, as seen in Fig.3. References [1] Zhang Z M, An Q, Li J W, et al. Piezoelectric friction-inertia actuator - A critical review

and future perspective[J]. International Journal of Advanced Manufacturing Technology, 2012, 62(5-8): 669-686.

Inkjet printing of thin metal-oxide structures from sol-gel-precursor inks A. Matavž,1,2,* R. C. Frunză,1 A. Drnovšek,1,2, B. Malič1,2, and V. Bobnar1,2

1Jožef Stefan Institute, Jamova cesta 39, 1000 Ljubljana, Slovenia 2Jožef Stefan International Postgraduate School, Jamova cesta 39, 1000 Ljubljana, Slovenia

*Corresponding Author: aleksander.matavz@ijs.si

The current trend to reduce the production costs of modern electronic devices has promoted the development of direct writing techniques, such as inkjet printing. Inkjet printing offers direct patterning of functional material with micrometer resolution and is suitable for cost-efficient production of large-area devices. However, inkjet-printed structures commonly dry in a way that the ring-like deposit is formed; the phenomenon is often referred to as “coffee stain” effect [1], which is usually deteriorating to the device performance. It has been shown that the uniformity of dried deposits can be improved by combining solvent and co-solvent having different boiling points and surface tensions, which induces the Marangoni flow during drying [2], however, the efficiency of this approach varies for different ink formulations.

We report the study on inkjet printing of highly uniform tantalum-oxide-based dielectric structures and exemplify the situation when the above-mentioned approach fails. We show that inks with a large fraction of co-solvents with high-boiling point show “coffee stain” effect after drying. By differential scanning calorimetry and drop evaporation study we relate the phenomenon to a much faster evaporation of the main solvent when compared to the co-solvent; consequently, the Marangoni flow exists only at the onset of drying. We solve the problem by adding the second co-solvent with high boiling point, which is capable of extending the duration of Marangoni flow and significantly improve the uniformity of dried deposits. By carefully adjusting the solvent composition of the ink, we were able to print remarkably flat, 45-nm-thick dielectric structures with well-defined lateral dimensions of 500×500 μm2 (Figure 1). Atomic force microscopy, profilometry, dielectric and electrical measurements proved that the developed ink formulation enables the deposition of high-quality, discrete structures with functional properties comparable to spin-coated films.

Figure 1. (a) Optical photograph, (b) cross-sectional profile, (c) 3D AFM topology image, and (d) leakage current characteristics of 45-nm-thick printed tantalum-oxide-based thin-film capacitors.

References [1] R. D. Deegan, O. Bakajin and T. F. Dupont, Nature, 389, 827–829 (1997) [2] E. Tekin, B. J. Gans, U. S. Schubert, J. Mater. Chem., 14, 2627–2632 (2004)

EPR Study of Ferroelectric Phase Transitions in Metal-Organic Frameworks Based on Perovskite Topology

M. Simenas,1,* A. Ciupa,2 M. Maczka,2 A. Pöppl3 and J. Banys1 1 Faculty of Physics, Vilnius University, Sauletekio 9, LT-10222 Vilnius, Lithuania

2 Institute of Low Temperature and Structure Research, Polish Academy of Sciences, P.O. Box 1410, PL-50-950 Wroclaw 2, Poland

3 Faculty of Physics and Earth Sciences, Universitat Leipzig, Linnestrasse 5, D-04103 Leipzig, Germany

*Corresponding Author: mantas.simenas@ff.vu.lt Recently, a novel type of porous materials called coordination polymers or metal-organic

frameworks (MOFs) emerged and immediately attracted attention of the scientific community [1]. These crystalline compounds are unique due to the highly porous structures which can be utilized for gas adsorption related applications. Additionally, many MOFs which contain paramagnetic transition-metal ions exhibit peculiar magnetic properties. The organic part in several of such compounds consists of polar molecules, which below a certain phase transition temperature order into a ferroelectric phase, making these materials single-phase hybrid multiferroics [2].

In this work we use continuous-wave and pulse EPR spectroscopy to investigate and characterize ferroelectric phase transitions in manganese and copper doped MOFs with general chemical formula [A][Zn(HCOO)3]x (where x = 1, 2 and Ax+ is molecular cation such as (CH3)2NH2

+) (Figure 1) [3]. The temperature dependent CW EPR spectra (Figure 1) reveal that the local paramagnetic ion-probes are indeed sensitive to the local structural changes occurring at the phase transitions. Spectral simulations were used to obtain the g, hyperfine and fine structure tensors and their temperature dependence which allowed to characterize the observed phase transition. Pulse EPR and ENDOR measurements were used to investigate structures of the frameworks in the low temperature phase.

Figure 1. High temperature phase of [(CH3)2NH2][Zn(HCOO)3] MOF [3].

References [1] S. Kitagawa, R. Kitaura, S. Noro, Angew. Chem. Int. Ed., 43, 2334, (2004) [2] W. Zhang, R. Xiong, Chem. Rev., 112, 1163, (2012) [3] P. Jain, N.S. Dalal, B.H. Toby, H.W. Kroto and A.K. Cheetham, J. Am. Chem. Soc., 130, 10450, (2008)

Fig. 1 The piezoelectric coefficient d24 versus temperature for quasi-single domain PMN-0.32PT crystals. The piezoelectric coefficient d24 was measured by the standard resonance method.

100 150 200 250 300 350

500

1000

1500

2000

2500

Piez

o. C

oeff.

d24

(pC/

N)

Temperature (K)

abnormal decrease

Observation of relaxor-PT single crystals at cryogenic temperatures: contribution from polar nanoregion

S. J. Zhang1*, F. Li2, J. Luo3, L. Q. Chen2 and T. R. Shrout2

1ISEM, AIIM, University of Wollongong, NSW 2500, AU 2Materials Research Institute, Pennsylvania State University, University Park, PA, 16802, US

3TRS Technologies, Inc., 2820 E. College Ave., State College, PA, 16801, US * Corresponding author: Shujun@uow.edu.au

Relaxor-PT single crystals have been extensively studied for ultrasonic transducer

applications, due to their ultra-high piezoelectric coefficients d33s > 1500pC/N and electromechanical coupling factors k33>90% [1-3]. The mesoscale mechanism(s) responsible for the ultrahigh piezoelectric activity of relaxor ferroelectrics have yet to be resolved. In this work, we report on recent developments of the dielectric and piezoelectric behavior of relaxor-PT single crystals at cryogenic temperatures, down to 30K. The temperature dependence of the piezoelectric coefficient d24 and dielectric permittivity ε22 for single domain PMN-0.32PT are shown in Figs. 1 and 2, respectively. A drastic decrease in both d24 (from 2000 to 750 pC/N) and dielectric permittivity ε22 at 10 kHz (18200 to 7800) were observed in the temperature range of 230-120 K. Furthermore, the decrease of permittivity ε22 was accompanied by an obvious dielectric relaxation (frequency dispersion) phenomenon. According to the phenomenological theory of ferroelectrics, the dielectric and piezoelectric response will decrease with temperature deviating from the corresponding phase transition point; meanwhile the rate of decrease will slow during this process, which is not the scenario observed. Thus, the observed decrease of d24 and ε22 cannot be explained by traditional phenomenological theory. It is generally accepted that the switching of polar nanoregions (PNRs) can highly contribute to the shear piezoelectric and transverse dielectric response for relaxor-PT crystals. Thus, the abnormal decrease of the shear piezoelectric coefficient and transverse dielectric permittivity at low temperatures (in Figs. 1 and 2) can be attributed to the “freezing” or slowing down of PNRs. In order to distinguish from the traditional PNR freezing, this phenomenon can be noted as “transverse polar freezing”, where the contributions of PNRs to shear piezoelectric and transverse dielectric activities in PMN-0.32PT crystals are on the level of >60%, which can also explain the ultrahigh piezoelectric observed in relaxor-PT crystals at room temperature.

References [1] S. Zhang and T. Shrout, IEEE Trans. Ultrason. Ferroel. Freq. Contr., vol. 57, 2138-46 (2010). [2] D. Damjanovic, M. Budimir, M. Davis and N. Setter, J. Mater. Sci., vol 4, 65-76 (2006). [2] S. J. Zhang and F. Li, J. Appl. Phys., vol. 111, 031301 (2012).

Fig. 2 Dielectric permittivity ε22 versus temperature for quasi-single domain PMN-0.32PT crystals. The crystal was poled along [011] direction while permittivity was measured along [100] direction.

100 150 200 250 300 350 4000.0

5.0k

10.0k

15.0k

20.0k

Temperature (K)

Die

lect

ric p

erm

ittiv

ity H 22

0.1 KHz 1 KHz 10 KHz

abnormal decrease

0.0

0.1

0.2

0.3

0.4

Loss

fact

or

Influence of texture on the piezoelectric properties of PZT-based high performance piezoceramic actuators M. Deluca,1,* P. Kaufmann,1 and P. Supancic2

1Department of Materials for Microelectronics, Materials Center Leoben Forschung GmbH, Roseggerstrasse 12, Leoben, Austria

2Institut fuer Struktur- und Funktionskeramik, Montanuniversitaet Leoben, Peter Tunner Strasse 5, Leoben, Austria

*Corresponding Author: marco.deluca@mcl.at Multilayer high-performance piezoelectric actuators (MPAs) based on lead zirconate titanate

(PZT) are currently the material of choice for fuel injection valves in the automotive sector (i.e. diesel common rail systems). Their popularity relies on the magnitude, the speed and precision of their response (in terms of elongation) to an applied electric field. MPAs have been the subject of intensive investigation in the past, with the goal of improving their performance by adjusting layer thickness and overall device design. The main issues influencing the performance of MPAs are the creation of cracks during poling between active and passive regions of the actuator, and the influence of external stresses on the achievable elongation. These aspects are intimately related with how the microscopic ferroelectric domain texture responds to external loads. In particular, crack propagation is influenced by the underlying domain texture, which could act as a toughening factor [1]. In addition, it is not clear if the measured performance improvement under low compressive loads is to be related with the domain texture.

In this work, polarised Raman measurements were performed on commercial MPAs both in the remanent state and in-situ - under applied electrical and mechanical loads close to the in-service conditions of MPAs. The results were interpreted with a newly developed Reverse Monte Carlo model that allows quantifying locally the texture distribution of ferroelectric domains [2]. Raman measurements revealed that the domain texture between electrodes in the active area of the MPA is strongly influenced by external electrical and mechanical loads; in particular a strong difference has been detected between remanent and field-induced texture. In MPAs where a passive zone is present, there is a strong texture gradient between active and passive zones, which can lead to the development of strong elastic stresses during poling. These aspects are decisive to understand the link between local texture and macroscopic performance of the MPA and contribute towards the tuning MPA of performances by judicious domain texture engineering.

Raman intensity / Calc. ODF / MPA Micrograph

Figure 1: Ferroelectric domain texture in MPAs as revealed by in-situ polarised Raman spectroscopy. From left to right: Raman intensity (experimental and fitted - red solid line), calculated Orientation Distribution Function (ODF), and micrograph of the MPA. From top to bottom: (a) Poled MPA: the preferential domain orientation is in the direction of poling. (b) Pre-stressed MPA: the preferential domain orientation is in the direction perpendicular to the axis of compression.

References [1] R. Bermejo, H. Grünbichler, J. Kreith, C. Auer, J. Eur. Ceram. Soc., 30, 705-712 (2010) [2] S. Röhrig, C. Krautgasser, R. Bermejo, J. L. Jones, P. Supancic, M. Deluca, J. Eur. Ceram. Soc., 35, 4321-4325 (2015)

Enhanced Ferroelectricity in (Ba0.6Sr0.4TiO3)1-x – (Sm2O3)x Vertically-aligned Nanocomposite Thin Films

Ady Suwardi,1,2,* Kui Yao1, OonJew Lee2 and Judith MacManus-Driscoll2 1Institute of Materials Research and Engineering, A*STAR (Agency for Science, Technology

and Research), 2 Fusionopolis Way, Innovis, #08-03, Singapore 138634 2Department of Materials Science and Metallurgy, University of Cambridge, 27 Charles

Babbage Road, Cambridge, United Kingdom CB3 0FS *Corresponding Author: as2334@cam.ac.uk

Ferroelectric Ba0.6Sr0.4TiO3 (BSTO) has been widely studied for its potential applications

ranging from dynamic random access memories, infrared detectors, microwave devices as well as hydrogen gas sensors due to its high dielectric constant, low dielectric loss as well as high tunability of dielectric permittivity. Vertically-aligned nanocomposite of BSTO and Sm2O3 (SmO) was reported to have strongly enhanced tunability while at the same time, maintaining the low loss in the material.[1] In this work, we report the effect of vertical interface straining by SmO phase on the ferroelectric properties of BSTO in various compositions of (BSTO)1-x – (SmO)x, with x ranging from 0.00 to 0.75 with increments of 0.25.

Figure 1. (a) Plot of tetragonality (bottom) and BSTO lattice parameter (top) as a function

of SmO fraction, x. (b) Polarization vs electric field of the nanocomposite with various SmO fractions, x.

As shown in Figure 1(a), the strain level of BSTO in both in-plane and out-of-plane strongly

depends on the SmO fraction, x. The possible strain mechanism can be associated with vertical interface epitaxy matching as well as thermal expansion coefficient mismatch between BSTO and SmO.[2] Figure 1(b) shows the P-E loop for various SmO fractions. The highest polarization (at x = 0.75) can be associated with the highest level of tetragonality in the BSTO phase. These results demonstrate a novel way to enhance ferroelectricity through strain control in nanocomposite films.

References [1] O. Lee, et al., "Extremely high tunability and low loss in nanoscaffold ferroelectric

films," Nano letters, vol. 12, pp. 4311-4317, 2012.

[2] J. MacManus-Driscoll, et al., "New strain states and radical property tuning of metal oxides using a nanocomposite thin film approach," APL Materials, vol. 3, p. 062507, 2015.

Deep understanding of PFM in ferroelectric domain imaging and characterization of polarization switching

F.X. Li,1,* H.C. Miao,1 and X.L. Zhou2 1College of Engineering, Peking University, Beijing, 100871, China

2College of Science, Wuhan University of Technology, Wuhan, 430070, China *Corresponding Author: lifaxin@pku.edu.cn

Piezoresponse force microscopy (PFM) had been widely used in characterization of electro-

active materials at nanoscale. Despite of its rapid development, the imaging principle of PFM may not be fully understood by most users, which may result in the misinterpretation of the obtained PFM images or curves. In this presentation, we will first show that some non-piezoelectric materials can still show significant PFM responses, and some non-ferroelectric materials show the ferroelectric-like SS-PFM phase hysteresis loops and amplitude butterfly curves. To interpret these phenomena, we proposed the sufficient conditions that a non-piezoelectric dielectrics can show significant PFM responses and that a non-ferroelectric dielectrics can show the ferroelectric-like SS-PFM loops. SS-PFM measurements and macroscopic D-E hysteresis loops measurements on a soda-lime glass and a non-ferroelectric dielectric material Ba0.4Sr0.6TiO3 verified our statements. Then, we show that PFM is very helpful in identifying the magnetic-field-induced ferroelectric domain switching in magnetoelectric (ME) composites and the SS-PFM curves under different magnetic fields can even be used to estimate the ME coefficient. Finally, we suggest that by combining PFM with another AFM-based technique-Atomic Force Acoustic Microscopy (AFAM), one can get more electromechanical information of functional materials at nanoscale.

Figure 1. The SS-PFM loops (a: amplitude butterfly loops; b: phase hysteresis loops) of a

Tefernol-D/PMN-PT two-layer magnetoelectric composite under different applied magnetic field

References [1] C.H. Miao, X.L. Zhou, X.Y. Wei, F.X. Li*, EPL 108, 27010 (2014) [2] C.H. Miao, X.L. Zhou, S.X. Dong, H.S. Luo, F.X. Li*, Nanoscale 6, 8515 (2014) [3] X.L. Zhou, F.X. Li*, H.R. Zeng, J Appl Phys 113, 187214 (2013)

Solidly Mounted Bulk Acoustic Wave switchable Ladder Filter Design on GaN/Sapphire Substrate Using MOSD

Almonir Mansour and T.S. Kalkur

Department of Electrical and Computer Engineering, University of Colorado, Colorado Springs, Colorado Springs, CO 80933

Gallium nitride (GaN) is considered as a wide band-gap semiconductor material with 3.4

eV bandgap at room temperture. The interest and excitement about GaN stems from two

intrinsic properties; it has wide band gap which is promising for high temperature

applications, and high breakdown fields than other materials such as, Si and GaAs. GaN

also has excellent electron transport properties such as, high saturated drift velocity and

exceptional carrier mobility, which makes it adequate for general electronics, and

particularly for microwave and power electronics.

In this paper we are presenting a design and fabrication of Solidly Mounted BAW

ladder filter on (0001) GaN/Sapphire (3.5um/430 um) substrate using BST with 70/30

composition as a thin film ferroelectric material. The BST thin film is deposited by

metalorganic solution deposition (MOSD) method and annealed at 800 oC temperature in

oxygen environment. A six layers of low and high acoustic impedance of SiO2/ Ta2O5,

with a thickness of half wave as a Bragg reflector, were built on the GaN/Sapphire

substrate using MOSD technique. The thickness of silicon dioxide and tantalum oxide

were characterized using Ellipsometer and found to be about 268 nm and 170 nm,

respectively. Furthermore, the device was characterized at low frequency to determine

the voltage capacitance relationship, and hence capacitance tunability. The tunability of

the capacitance as a function of applied voltage was found to be 44.85 % at 1 MHz. Also,

BAW ladder filter was fabricated on the same substrate as SMR type and showed a

switchable and tunable response at switching frequency of 4.85 GHz and tunability of

frequency of about -0.85 % at 11 V. Moreover, we characterized the device over a range

of temperature from room temperature (RT) to 120 oC to see its effect on FBAR

parameters such as, series and parallel frequency (fs, fp), quality factor and effective

electromechanical coupling coefficient (Keff). Also, temperature coefficient of frequency

(TCF) over the same range of temperature was extracted and found to be -19 ppm/oC.

Structure-property-processing relationships in modified Bi(B’B”)O3-based piezoelectrics

Ben Kowalski1, Alp Sehirlioglu1

1Materials Science & Engineering, Case Western Reserve University, 10900 Euclid Ave, Cleveland, USA *Corresponding Author: bak121@case.edu

In recent years there has been an intense push for high temperature piezoelectrics for

applications in both terrestrial and aerospace territories. For years the operating temperature limit, usually taken as ½ the Curie temperature (Tc), has been ~200°C for one of the most widely used commercial piezoelectrics, Pb(Zr,Ti)O3 (PZT). Subsequent research into Bi(B’B”)O3-based piezoelectrics led to the discovery of promising high temperature systems in concert with Pb-based end members, namely PbTiO3, in addition to Pb-free systems. Morphotropic phase boundary (MPB) systems containing BiScO3 and BiFeO3, among others have been shown to have high Tc’s and display thermally stable electromechanical properties up to high temperature.1,2 While the Tc marks the boundary between the ferroelectric-paraelectric state, it is also necessary to determine the depoling temperature (Td) which dictates the actual working temperature range. This work will investigate this working temperature range for promising Pb- and Pb-free systems with B-site modifications against commercial PZT under the simultaneous effects of electric field, frequency, and temperature in addition to the characterization of microstructure.

The fundamental radial resonance peak is shown in Fig. 1 as a function of frequency,

temperature, and phase angle for compositions near the MPB in BS-PT and BS-PT with Bi(Zn0.5Zr0.5)O3 ternary addition. This method reveals multiple aspects of the material through the shape of the phase angle peak that can be overlooked. It is seen that instead of a single depoling temperature, there is actually a depoling onset (Td

onset) which corresponds to a narrowing of the phase angle peak indicating that depoling can be a two-step process. Additionally, there is a softening occurring in the rhombohedral compositions at higher temperatures evidenced by the bend in the phase angle peak, that is absent in the tetragonal BZZ5 composition. This method can be used to help identify and compare promising materials for high temperature piezoelectric applications. Funding Source: NASA GSRP Fellowship NNX11AL17H References [1] R. Eitel, C. Randall, et al., Jpn. J. Appl. Phys., vol 40, pp. 5999–6002 (2001) [2] M.S.B. Darby, D.V. Karpinsky, et al., Thin Sold Films, vol 531, pp 56-60 (2013)

Tc Tdfinal

Tdonset

T (°

C)

Figure 1: Phase angle for the fundamental radial resonance peak as a function of temperature and frequency for various compositions.

Fabrication and characterization of Ba(ZrxTi1-x)O3 nanocube 3D assembly films K. Mimura,1,* Q. Ma,1 and K. Kato1

1National Institute of Advanced Industrial Science and Technology, 2266-98 Anagahora Shimoshidami Moriyama, Nagoya, Japan

*Corresponding Author: k.mimura@aist.go.jp Nanocrystal is defined as nano-sized single crystal with precise control of their size

distribution and shape such as cube, cuboid, rod, octahedron, and so on. Nanocrystals attract a great deal of attention due to the unique properties attributed by their shapes and sizes. Especially, dielectric nanocube is strongly expected to be used as a component of the new generation devices. BaTiO3 nanocubes (BT NCs) have been synthesized by hydrothermal method with aqueous complex and surfactant. [1] The BT NC 3D assembly was fabricated by self-assembly method. [2, 3] The BT NC assemblies heat-treated at 800-900˚C showed high dielectric constant above 3000 with relative low loss tangent due to high quality single crystals and numerous interfaces. [4, 5] On the other hand, the tuning of the dielectric properties is important to use the devices. Substitution of Ti ion by Zr on BT is well-known method to flatten the temperature dependence of dielectric properties. [6] In this study, we synthesized Ba(ZrxTi1-x)O3 nanocubes (BZTx NCs) by hydrothermal method with aqueous Ti and Zr complex and surfactants. BZTx NCs (about 20 nm) with sharp edges were obtained when x≤0.2. The elemental mapping of BZT0.2 NCs was characterized by STEM-EDX as shown in Fig. 1a-1e. Ti sites were considered to be homogeneously substituted by Zr ions. Composition of BZT0.2 NCs was nearly equal to the nominal ratio. BZTx NC ordered assembly was fabricated by dip-coating with capillary-force-assisted self-assembly method (Fig. 1f). Dielectric properties of BZTx NC assembly films will be discussed.

Figure 1. (a) HAADF-STEM image of BZT0.2 NCs. EDX mapping of (b) O, (c) Ba, (d) Zr,

and (e) Ti. (f) SEM image of BZT0.2 NC assembly film fabricated by dip-coating method.

A part of this work was supported by the Advanced Low Carbon Technology Research and Development Program (ALCA) of Japan Science and Technology Agency (JST).

References [1] F. Dang, K. Mimura, K. Kato et al., Nanoscale, 4, 1344-1349 (2012) [2] K. Mimura, K. Kato et al., Appl. Phys. Lett., 101, 012901 (2012) [3] K. Mimura, K. Kato, J. Nanopart. Res., 15, 1995 (2013) [4] K. Mimura, K. Kato, Appl. Phys. Express, 7, 061501 (2014) [5] K. Mimura, K. Kato, Jpn. J. Appl. Phys., 53, 09PA03 (2014) [6] P. S. Dobal et al., J. Appl. Phys., 89, 8085-8091 (2001)

(a) (c)

(e)(d)

(b)

10nm

10nm

10nm 10nm

10nm

(f)

Peculiarities of relaxor to ferroelectric phase transition in 0.1Na0.5Bi0.5TiO3-0.6SrTiO3-0.3PbTiO3 solid solutions

Š. Svirskas,1,* J. Banys,1 V. V. Shvartsman,2 D. Lupascu,2 M. Dunce3, E. Birks3, R. Ignatans3

1Faculty of Physics, Vilnius University, Sauletekio av. 9/3b., Vilnius, Lithuania 2Institute for Materials Science and Center for Nanointegration Duisburg-Essen (CENIDE),

University of Duisburg-Essen , Universitätsstrasse 15, Essen, Germany 3Institute of Solid State Physics, University of Latvia, Kengaraga 8, Riga, Latvia

*sarunas.svirskas@ff.vu.lt Sodium bismuth titante (Na0.5Bi0.5TiO3) is one of the most promising lead-free piezoelectric

materials. Recently, multi-component solid solutions based on Na0.5Bi0.5TiO3 have attracted significant attention [1, 2]. Such solid solutions may drastically enhance piezoelectric properties of the parent material. Moreover, sometimes it is possible to increase the depolarization temperature, as well as to reduce the dielectric losses and conductivity.

This report deals with 0.4Na0.5Bi0.5TiO3-0.6SrTiO3 solid solutions with addition of lead titanate (PbTiO3). Particular compositions of this family have a spontaneous 1st order phase transition from relaxor to ferroelectric state. The aim of this report is to discuss the origin and peculiar behavior of this phase transition in the 0.1Na0.5Bi0.5TiO3-0.6SrTiO3-0.3PbTiO3 (0.1NBT-0.6ST-0.3PT) solid solution.

The report concentrates on the results of several experimental techniques. The X-ray diffraction, broadband dielectric spectroscopy experiments were carried out. In addition, the measurements of polarization, displacement and pyroelectric current measurements were performed. The temperature dependence of remnant polarization extracted from measurements of pyroelectric current shows an unusual critical exponent β (P ~ (T-Tc)β). The critical exponents which do not coincide with Landau-Ginzburg-Devonshire (LGD) theory were already reported for several relaxor-like systems [3]. There are several interpretations of such behavior: 1) the deviation from the LGD theory is related to the rich defective states in the material [4], 2) according to Kleemann some relaxor systems have critical exponents which are consistent with random-field Ising model [5, 6].

The broadband dielectric spectroscopy data show large dispersion above the phase transition temperature in microwave region. Such behavior resembles the order-disorder type ferroelectrics although obvious critical slowing down is not observed. It is important to stress that at temperatures above the phase transition the ferroelectric state can be induced by external electric field in a significant temperature interval. This allows us to attribute the high temperature phase as a relaxor phase.

Finally, the nanoscale measurements by piezoresponse force microscopy (PFM) revealed unusual behavior of local polarization. There exist several types of grains which have very different domain structure and show different temperature dependences of the local piezoresponse. This may explain the peculiar macroscopic response of the material under investigation. It seems that some kind of frustration exists between the different grains which complicate the formation of long range order, thus giving rise to a relaxor-like properties at elevated temperatures. The relation between the microscopic and macroscopic properties will be revealed in the report and discussed in more detailed manner.

References [1] J. Roedel, W. Jo et al. J. Amer. Ceram. Soc., vol. 92(6) 1153-1177 (2009) [2] D. Damjanovic, N. Klein et al. Funct. Mater. Lett., 03, 5 (2010) [3] P. Lehnen, W. Kleemann et al., The European Physical Journal B, vol. 14, 633-637 (2000) [4] J. F. Scott, J. Phys.: Cond. Matt., vol. 18, 7123–7134 (2006) [5] W. Kleemann, J. Dec et al. Europhys. Lett.,vol. 57, 14 (2002) [6] W. Kleemann, J. Mat. Sci., vol. 41, 129-136 (2006)

The Creation of the Piezoresponse Force Microscopy (PFM) 23 Years AgoK. Franke 1,*, L. Eng 2, M. Weihnacht 3, J. Besold 4, W. Haessler 3

1 Retired, Striesener Str. 40 d, 01307 Dresden, Germany 2 Institut für angewandte Physik (IAP), TU Dresden, Beyerbau, George-Baerstrasse, 01069

Dresden, Germany3 Institut für Festkörper- und Werkstoffforschung (IFW), Helmholtzstrasse 20, 01069

Dresden, Germany4 TGZ GmbH, Preuschwitzer Str. 20, 02625 Bautzen, Germany

* Corresponding Author: frankekurt@gmx.de

The voltage-induced thickness variations of piezoelectric samples are in the range of one Angstrom unit only. Therefore, the creation of PFM is performed when such small deformations can be reliably measured, i.e. with low noise and down to some picometres. We first succeeded in doing in February 1993.

Our initial competence for it was got in the 80ths on measuring surface acoustic waves (SAW) on piezoelectrics developed in Dresden, Germany. By the use of special light fibre and selected pulse-like laser we could construct some interferometers both for high-resolving SAW- and later PFM measurements. The principle of light fibre interferometer is explained and three methods to minimize noise too. The access to scanning tunnelling technique in the early 90ths enabled the rapid start of our home made high-resolving PFM [1].

The very first and some nicely later pictures are shown together with different polarization experiments [2]. It is discussed what physical quantities contribute in the simultaneously measured three pictures of the PFM. A funny summary is given.

References[1] K. Franke, J. Besold, W. Haessler, C. Seegebarth, Surface Science Letters, 302, L283-

L288 (1994)[2] K.Franke, H. Huelz, M. Weihnacht, W. Haessler, J. Besold; Ferroelectrics, 172,

397-404(1995)

Transport and defect mechanisms in BaTiO3-Bi(Me)O3 ceramics for high temperature and energy density capacitor applications

Nitish Kumar,1,* Eric A. Patterson,2 Till Frömling,2 and David P. Cann1 1Materials Science, School of Mechanical, Industrial, and Manufacturing Engineering, Oregon

State University, Corvallis, Oregon, USA 2Institute of Materials Science, Technische Universität Darmstadt, Darmstadt, Germany

*Corresponding Author: nitishkumar.iitk@gmail.com Ceramics based on BaTiO3-Bi(Me)O3 exhibit excellent properties (dielectric permittivity >

1000, high breakdown strength) for dielectric applications, which also remain stable with temperature and electric field. Multilayer ceramic capacitors based on these materials have demonstrated energy densities approaching ~3 J/cm3, which is superior to commercially available devices. However, their underlying defect chemistry and transport properties need to be fully understood before they can be fully exploited for capacitor applications. Recently, it was shown that there was a significant improvement in electrical resistivity in BaTiO3-Bi(Me)O3 ceramics on addition of Bi(Me)O3 to solid solution, which was also accompanied by a change in the polarity of the majority charge carrier from p-type for BT to n-type for the BaTiO3-Bi(Me)O3 solid solution. This pointed towards an unintended “effective” donor doping in BT-Bi(Me)O3 ceramics on addition of Bi(Me)O3.

Figure 1. Arrhenius plots of resistivity for BaTiO3-Bi(Me)O3 ceramics Taking a specific example of BT-Bi(Zn1/2Ti1/2)O3 (BT-BZT), the origin of the same was

investigated. Even though there is no obvious mechanism for donor doping in these ceramics, the cause may be linked to the formation of an intermediate phase BaBiO3 with Bi5+ on the B-site, the presence of oxygen vacancies being compensated by electrons, the loss of zinc and bismuth during processing, and other mechanisms. With the help of techniques like high-energy diffraction, prompt-gamma neutron activation analysis, XPS, TGA with in-situ mass spectroscopy, EELS and other experiments, this presentation will include findings which aim to help understand the underlying defect mechanisms in these ceramics. Finally, it will be shown that this understanding of defects can be used to tune properties e.g. insulation properties can be improved to make these ceramics better-suited for applications like high temperature dielectrics or ionic conduction can be increased to make them better suited for applications like oxygen-ion conduction.

References [1] N. Kumar and D. P. Cann, Journal of the American Ceramic Society, 98[8] 2548-55 (2015) [2] N. Kumar, E. A. Patterson, T. Frömling, and D. P. Cann, Journal of Materials Chemistry C, 4[9] 1782-86 (2016) [3] N. Kumar, E. A. Patterson, T. Frömling, and D. P. Cann, Journal of the American Ceramic Society (under revision) (2016)

103

105

107

109

1011

0.0012 0.00135 0.0015 0.00165 0.0018

BTBT-BiScO3BT-Bi(Ni1/2Ti1/2)O3BT-Bi(Zn1/2Ti1/2)O3

1/Temperature (K-1)

Res

istiv

ity (Ω

-cm

)

560 468 394 333 283Temperature (°C)

Bi0.5Na0.5TiO3-BaTiO3:ZnO composites, improved property’s temperature stability and beyond

Shan-Tao Zhang*

1Department of Materials Science and Engineering, Nanjing University, Hankou Road 22,

Nanjing, China *Corresponding Author: stzhang@nju.edu.cn

ZnO particles were embedded into Bi0.5Na0.5TiO3-BaTiO3 (BNT-6BT) matrix to form 0-3

type lead-free piezoelectric composite. The depolarization temperature increases with increasing ZnO concentration until depolarization disappears at 30 mol% ZnO. We propose that the semiconducting nature of ZnO provides charges to partially compensate the ferroelectric depolarization field. In addition, such a composite can enhance the photoluminescence of lanthanide ion by a factor of 5.5 times, electric poling further enhances the photoluminescence. We hope this work can be helpful for the understanding of the mechanism of depolarization, as well as for developing multifunctional materials.

References [1] J. Zhang, Z. Pan, F. F. Guo, W. C. Liu, H. P. Ning, Y. B. Chen, M. H. Lu, B. Yang, J. Chen,

S. T. Zhang, X. R. Xing, J. Rödel, W. W. Cao, Y. F. Chen, Nature Communications 6, 6615 (2015)

[2] J. Zhang, Z. Pan, P. X. Nie, Y. S. Cui. B. Yang, J. Chen, S. T. Zhang, Appl. Phys. Lett. 106, 232904 (2015)

Novel perovskite-type ferroelectrics with high Curie temperature and piezoresponse

Jian Yu1,2*, Linlin Zhang,2 Xianbo Hou,2 Yang Lin,2 and Weilin Zheng2

1Functional Materials Research Laboratory, Donghua University, Shanghai 201620, China

2Functional Materials Research Laboratory, Tongji University, Shanghai 201800, China

*Corresponding Author: jyu@tongji.edu.cn

With the global requirements for increased efficiency and safety, piezoelectric sensors have been pursued to meet the increasing demand in applications of pressurized water reactors, flow monitoring in oil and gas plant, and position sensing in aerospace, which integrates relatively simple device packaging that can withstand elevated temperature ranges above 200oC, to condition monitoring and acoustic non-destructive testing. As the present candidate, tungsten-bronze-structured PbNb2O6 and Aurivillius-structured Bi4Ti3O12 ferroelectrics exhibit higher ferroelectric Curie temperature (TC) above 500°C but relatively low piezoresponse.

In this talk, we will present how-to design novel perovskite-type ferroelectrics with similar TC but higher piezoresponse than the PbNb2O6 and Bi4Ti3O12 systems. Through data-mining within materials genome approach, two quantitative relationships of 𝑇𝑇𝐶𝐶(𝜇𝜇) = 𝑎𝑎 + 𝑏𝑏𝜇𝜇 + 𝑐𝑐𝜇𝜇2 (μ is reduced mass of ABO3 unit cell)1,2 and 𝑑𝑑33 = 𝑎𝑎𝜀𝜀33 − 𝑏𝑏𝜀𝜀332 (ε33 is dielectric constant after poling ceramics)3,4 are obtained for perovskite-type ferroelectrics. Therefore, the principles to choose element and construct structural phase boundary are purported and relevant experiments on perovskite-structured BiFeO3-Bi(Zn1/2Ti1/2)O3-PbTiO3 (BF-BZT-PT) and BiFeO3-Bi(Zn1/2Ti1/2)O3-BaTiO3 (BF-BZT-BT) ternary solid solutions carried out.3-5 The structural phase boundary was determined by powder X-ray diffraction and found strongly influenced by ceramic microstructure grain size. The structural phase boundary is intrinsically benefiting for high piezoresponse while residual internal tensile stresses play extrinsic role to pin ferroelectric polarization switching and cause non-full poling for those BZT-riched ceramics.4-6 BF-BZT-PT and BF-BZT-BT systems are becoming promising candidate for future high temperature applications or lead-free applications because extended structural phase boundary provides big space to adjust piezoelectric performance and aging stabilities by changing composition.

Table I. Summary of piezoelectric property for BF-BZT-PT and BF-BZT-BT ceramics obtained in our work. Those for commercial lead titanate (MLT), lead metaniobate (BM901) and bismuth titanate (K-15) ceramics with Curie temperature above 490°C are also presented for comparison.

ε33T/ε0

(εr) tanδ d33

(pC/N) TC

(°C)

0.05wt%MnO2-doped 0.70BF-0.04BZT-0.26PT 183 0.015 28 640 This work 0.70BF-0.08BZT-0.22PT 177 0.030 29 > 650 This work 0.66BF-0.15BZT-0.19PT (217) 0.020 24 630 This work 0.60BF-0.14BZT-0.26PT 264 0.020 16 590 This work 0.59BF-0.15BZT-0.26PT 258 0.023 41 582 This work 0.53BF-0.15BZT-0.32PT 302 0.021 30 560 This work 0.07wt%MnO2-doped 0.68BF-0.10BZT-0.22BT 504 0.055 70 630 This work 0.17wt%MnO2-doped 0.69BF-0.04BZT-0.27BT 578 0.034 145 510 This work 0.22wt%MnO2-doped 0.696BF-0.014BZT-0.29BT 660 0.033 150 513 This work Lead Titanate(MLT) 170 0.008 51 495 commercial Lead Metaniobate(BM901) 325 0.01 90 490 commercial Bismuth Titanate (K-15) 140 0.03 18 ~620 commercial

References [1] L.L. Zhang, J. Yu*, M. Itoh, J. Appl. Phys. 115, 123523(2014). [2] J. Yu*, F.F. An, F. Cao, Jpn. J. Appl. Phys. 53, 051501 (2014). [3] X.B. Hou, J. Yu*, J. Am. Ceram. Soc. 96(7), 2218 (2013). [4] L.L. Zhang, X.B. Hou, J. Yu*, Jpn. J. Appl. Phys. 54, 081501 (2015). [5] Y. Lin, L.L. Zhang, W.L. Zheng, J. Yu*, J. Mater. Sci.: Mater. Electron. 26(10), 7351 (2015). [6] L.L. Zhang, J. Yu*, Appl. Phys. Lett. 106, 112907 (2015).

Negative capacitance: theory, practice and limitations Y.J. Kim, M.H. Park, and C.S. Hwang*

Department of Material Science & Engineering and Inter-University Semiconductor Research Center, Seoul National University, Seoul 151-744, Republic of Korea

*Corresponding Author: cheolsh@snu.ac.kr

The negative capacitance (NC) effects in ferroelectric materials have emerged as the

possible solution to low-power transistor devices and high-charge-density capacitors. This is fundamentally based on the total energy argument of dielectric/ferroelectric (DE/FE) stacked film using the Landau-Ginzburg-Devonshire (LGD) theory. Although the steep switching characteristic (subthreshold swing <sub-60mV/dec) has been demonstrated in various devices combining the conventional transistors with ferroelectric gates, the actual applications of the NC effects are still some way off owing to the inherent hysteresis problem. Capacitance enhancement from the stacked DE/FE compared with the single layer DE has been reported under a limited circumstances, but direct proof for charge boosting has not been rigorously reported. This talk will start with the discussions on the possible problems related with recent claim on the direct observation of a NC effect from a single layer epitaxial Pb(Zr0.2,Ti0.8)O3 (PZT) thin film [1], and alternative interpretations that can explain the experimental results without invoking the NC effect are provided.[2]

Then, the presentation will cover a topic of “Why the NC effect is not seen even when it is supposed to be seen based on the LGD theory?” For this purpose, this work adopted a modified formalism to incorporate the depolarization effect to describe the energy of the general DE/FE system [3]. The model predicted that the SrTiO3/BaTiO3 system will show a capacitance boost effect. It was also predicted that the 5nm-thick Al2O3/150nm-thick BaTiO3 system shows the capacitance boost effect with no FE-like hysteresis behavior, which was inconsistent with the experimental results; the amorphous-Al2O3/epitaxial-BaTiO3 system showed a typical FE-like hysteresis loop in the polarization – voltage test. This was due to the involvement of the trapped charges at the DE/FE interface, originating from the very high field across the thin Al2O3 layer when the BaTiO3 layer played a role as the NC layer. Therefore, the NC effect in the Al2O3/BaTiO3 system was frustrated by the involvement of reversible interface charge; the highly stored charge by the NC effect of the BaTiO3 during the charging period could not be retrieved during the discharging process because integral part of the polarization charge was retained within the system as a remanent polarization [3].

This part will be succeeded by the third part on how to improve the circumstance and to see the actual charge boosting from the DE/FE layer. This was accomplished by reinterpreting the hysteretic properties of the NC effects within the time domain, and demonstrated that capacitance (charge) boosting could be achieved without the hysteresis from the Al2O3/BaTiO3 bilayer capacitors through short-pulse charging [4]. This work revealed that the hysteresis phenomenon in NC devices originated from the dielectric leakage of the dielectric layer. The suppression of charge injection via the dielectric leakage, which usually takes time, inhibits complete ferroelectric polarization switching during a short pulse time. It was demonstrated that a non-hysteretic NC effect can be achieved only within certain limited time and voltage ranges, but that these are sufficient for critical device applications.

References [1] A.I. Khan et al., Nat. Mater. 14, 182-186 (2015). [2] S.J. Song et al., Sci. Rep. 6, 20825 (2016). [3] Y.J. Kim et al., Sci. Rep. 6, 19039 (2016). [4] Y.J. Kim et al., (Submitted to Nano Lett.).

Evolution of Interface Structure in BaTiO3 Nanocube Assemblies for Enhanced Dielectric Properties

Kazumi Kato, Qiang Ma, Zheng Liu, Ken-ichi Mimura, Kyuichi Yasui National Institute of Advanced Industrial Science and Technology, 2266-98 Anagahora,

Shimoshidami, Moriyama, Nagoya, Japan *Corresponding Author: kzm.kato@aist.go.jp

Single crystalline {100} dominant BaTiO3 nanocubes were synthesized by the hydrothermal

method using aqueous sources of Ba and Ti, and organic additives [1]. The 15nm-sized nanocube has been addressed as a building block to develop hierarchical structures in which the nanocubes were assembled with the 4-fold symmetry along both vertical and horizontal directions [2]. Small capacitors consisting of the BaTiO3 nanocube ordering assemblies and platinum electrodes exhibited higher dielectric constant and relatively low loss of 4000 and 0.07, respectively [3,4]. In addition, the anisotropy in shape of the nanoblocks was considered to be strongly associated with the ferroelectricity [5]. Recently, the precise characterization of BaTiO3 nanocube itself and interfaces developed between the adjacent nanocubes with small tilting angles were performed using advanced TEM methods. The nature at relatively high temperatures was analyzed. By in-situ analysis of the nanocube at 773K, the hopping movement of atoms at the surface and the surface reconstruction were confirmed although the inner atomic arrangement has been fixed as a perfect perovskite structure [6]. On the other hand, the lattice fringes of the adjacent nanocubes after heating at a certain temperature range of 1023K to 1073K struggled while getting together to give moire patterns. The edge dislocations locally formed after heating at 1073K to 1173K. Then finally, the series of edge dislocations or small angle grain boundary (Fig. 1), stacking faults and waved lattice fringe appeared after heating at relatively high temperature range of 1173K to 1223K [7]. From these characteristic behaviors, the adjacent nanocubes with small tilting angles were found to bond each other to generate misfit strain. The consequent geometric appearances were consistent with the enhanced dielectric properties of 3D nanocube ordering assemblies.

Figure 1. Typical TEM and FFT filtered images of the interface between the adjacent nanocubes heated at 1173K [7].

A part of this work was supported by the Advanced Low Carbon Technology Research and

Development Program (ALCA) of Japan Science and Technology Agency (JST). References [1] F. Dang, K. Mimura, K. Kato, H. Imai, S. Wada, H. Haneda, M. Kuwabara, Nanoscale, 4, 1344 (2012); [2] K. Mimura and K. Kato, J. Nanopart. Res., 15, 1995 (2013); [3] K. Mimura, K. Kato, H. Imai, S. Wada, H. Haneda, M. Kuwabara, Appl. Phys. Lett., 101, 012901 (2012); [4] K. Mimura, K. Kato, Applied Physics Express, 7, 061501 (2014); [5] Q. Ma, K. Kato, submitted; [6] Z. Liu, K. Kato, unpublished; [7] Q. Ma, K. Kato, CrystEngComm, 18, 1543 (2016)

5 nm

BaTiO3

nanocube A

BaTiO3

nanocube B

Investigating Morphotropic Phase Boundary of PbZr1-xTixO3 from the Local Scale N. Zhang,1,* H. Yokota,2 A. M. Glazer,3 W. Ren1, and Z.-G. Ye1,4

1Electronic Materials Research Laboratory, Key Laboratory of the Ministry of Education & International Center for Dielectric Research, Xi’an Jiaotong University, Xi’an 710049, China

2Department of Physics, Chiba University, Japan 3Department of Physics, University of Oxford, Oxford, United Kingdom

4Department of Chemistry and 4D LABS, Simon Fraser University, Burbaby, Canada *Corresponding Author: nzhang1@xjtu.edu.cn

The crystal structure and its relationship with the high piezoelectric performance of PbZr1-

xTixO3 (PZT) have been under extensive studies for many years, especially with compositions near the morphotropic phase boundary (MPB) where its piezoelectric properties reach the peak values. Traditionally, in the average structure scale, the structure evolving process has been widely accepted as rhombohedral-monoclinic-tetragonal phase transitions, with the monoclinic Cm in the MPB acting as a bridging phase. However, in our recent high-resolution powder diffraction experiments and pair distribution function analyses studies at room temperature, the presence of the monoclinic phase has been found in the local scale with different coherent lengths across a wide composition range from the MPB to the rhombohedral region, with a MB-MA phase change. This explains the rapid increase of the piezo-activity of PZT on approaching MPB from the rhombohedral side in terms of both intrinsic and extrinsic contributions1. On the other hand, at high temperatures, the local arrangements of oxygen octahedra tilts remain even in the cubic phase2. Increasing amount of evidences shows that when viewing the crystal structures from the local scale, new phenomena are frequently found. Therefore, in order to fully understand the temperature- / composition- induced phase transitions and the structure-property relationships in ferroelectric materials, a thorough investigation from the local structure point of view is essential.

Figure 1. Updated phase diagram of PZT containing the local structure information

On the basis of the local structure studies of PZT in the rhombohedral compositions, we

carry on with the pair distribution function analyses in the MPB region and towards the tetragonal side. The local phase transition process across the MPB has been systematically studied. The local distribution of the Pb displacements and their directions are plotted out for different compositions. This reveals a different phase transition mechanism from the understanding of the average structure.

References [1] N.Zhang et al., Nature Comm., 5, 5231 (2014) [2] N.Zhang et al., J. Appl. Cryst., 48, 1637-1644 (2015)

High-temperature characterization of langasite Ca3NbGa3-xAlxSi2O14 single crystals

T. Karaki,1,* M. Kobayashi,1 N. Shimota,1 T. Fujii,1 M. Adachi,1 Y. Ohashi,2 J. Kushibiki,2 and A. Yoshikawa2

1Faculty of Engineering, Toyama Prefectural University, Imizu, Toyama 939-0398, Japan 2Faculty of Engineering, Tohoku University, Sendai 980-8579, Japan

*Corresponding Author: chen@pu-toyama.ac.jp Piezoelectric langasite-family single crystals have the point group 32 and general chemical

formula A3BC3D2O14. There are mine cation sites in which cations would be substituted by others.1–2) In our primary work,3) we have successfully grown one of the langasite-family single crystals, Ca3NbGa3Si2O14 (CNGS) by a Czochralski method. The CNGS has a melting point of about 1325 oC, so the crystal growth could be carried out in air or oxygen atmosphere using a Pt crucible. Since the langasite crystals have no phase transition until their melting point, high-performance pressure sensors operating under a high-temperature environment, for example, higher than 600 oC, have been expected for applications in automobile engines and turbines recently.4–12)

The langasite-family single crystals have a problem of low resistivity and high dielectric loss at high temperatures. It has been reported that by substituting Al for Ga, langasite-type crystal La3Ta0.5Ga5Al0.5O14 (LTGA05) showed a high electrical resistivity at high temperatures.11) We also reported that Al-substituted Ca3NbGa3-xAlxSi2O14 (CNGAS) (x=0.1–0.8) single crystals showed a great improvement of electrical resistivity at high temperature.12)

In this work, CNGAS (x=1.0) single crystals were grown and the electric resistivity in a high temperature range was substantially improved comparing with that of CNGAS (x=0.8) specimen. The specimen had an electric resistivity of 1010 :cm at 520 oC. From the dependence of the resistivity on temperature, an activation energy of about 1.2 eV was obtained. However, the dielectric features associated with loss tangent (10 kHz) increase at about 600 oC was not improved by the Al substituent. It is considered that the loss tangent associated with an alternating electric field has a different mechanism from the electric resistivity associated with a direct current field. The origin of the loss tangent change needs further investigation.

References [1] A. A. Kaminskii, I. M. Silvestrova, and G. A. Denisenko, Phys. Status Solidi A 80, 607 (1983). [2] A. B. Ilyaev, B. S. Umarov, L. A. Shabanova, et al., Phys. Status Solidi A 98, K109 (1986). [3] T. Karaki, R. Sato, M. Adachi, J. Kushibiki, et al., Jpn. J. Appl. Phys. 43, 6721 (2004). [4] T. Karaki, T. Lv, M. Adachi, Y. Ohashi, et al., Jpn. J. Appl. Phys. 51, 09LD09 (2012). [5] H. Fritze, H. L. Tuller, G. Borchardt, and T. Fukuda, MRS Proc. 604, 65 (1999). [6] H. Takeda, S. Tanaka, S. Izukawa, et al., Proc. IEEE Ultrasonics Symp., 2005, p. 560. [7] H. Takeda, S. Tanaka, H. Shimizu, T. Nishida, et al., Key Eng. Mater. 320, 239 (2006) [8] I. H. Jung, T. Fukuda, and K. H. Auh: J. Electroceram. 13, 471 (2004). [9] S. Zhang, A. Yoshikawa, K. Kamada, E. Frantz, et al., Solid State Commun. 148, 213 (2008). [10] H. Takeda, S. Tanaka, T. Nishida, et al., Trans. Mater. Res. Soc. Jpn. 31, 11 (2006). [11] H. Takeda, J. Yamaura, T. Hoshina, and T. Tsurumi, J. Ceram. Soc. Jpn. 118, 706 (2010). [12] T. Karaki, M. Kobayashi, S. Song, T. Fujii, et al., Jpn. J. Appl. Phys. 54, 10ND07, (2015).

The improvement of the piezoelectric properties in Pb(Ni

ceramics by grain orientation

Y. Miwa1

1Murata Manufacturing Co., Ltd., 102Ceramic Laboratory, École Polytechnique Fédérale de Lausanne,

*Corresponding Author:

Pb(Ni1/3Nb2/3)O3-Pb(Zr,Ti)Opiezoelectric properties, and However, a much higher electromechanical coefficientfor miniaturization of these device

One of the solutions to The piezoelectric properties of certain direction. Therefore, many

We employed a magnetic alignment method to fabricate oriented PNNceramic slurry, which consists of calcinedinto a mold under a high magnetic field up to 9Tceramics were obtained by sintering these green compacts without magnetic field.

The sintered sample was cutdielectric, piezoelectric, and pyroelectric properties were measured by impedance analyzer as a function of orientation direction. showed strong dependence on the orientation direction, and they were maximized perpendicular to the driving electric field and vibration directionThe maximum value of electsample.

Figure 1. The dependence of electromechanical coefficient

The distribution of grain direction was also analyzed, it Mises-Fisher distribution[2]. We will distribution on the piezoelectric properties

References

[1] Y. Miwa et al, Appl. Phys. Express[2] X. Lu, S. Hanagud, IEEE

0

0.1

0.2

0.3

0.4

0.5

0.6

k 31

The improvement of the piezoelectric properties in Pb(Ni1/3Nb

ceramics by grain orientation and their dependence on the orientation direction

1,*, D. Damjanovic

2, K. Ogiso

1, and S. Kawada

Murata Manufacturing Co., Ltd., 10-1 Higashikotari 1-chome, Nagaokakyo, Kyoto, JapanCeramic Laboratory, École Polytechnique Fédérale de Lausanne, Lausanne, Switzerland

Corresponding Author: miwa_y@murata.com

Pb(Zr,Ti)O3 (PNN-PZT) ceramics are well known for piezoelectric properties, and are used for many kinds of devices such as actuators and sensors.

electromechanical coefficient and a piezoelectric constantdevices and for new applications such as energy harvesting.

One of the solutions to achieve the requirement is through ceramics with oriented e piezoelectric properties of oriented ceramics are anisotropic, and

many kinds of orientation methods are studied.We employed a magnetic alignment method to fabricate oriented PNN

ceramic slurry, which consists of calcined PNN-PZT powder, water, and dispersant, was cast a high magnetic field up to 9T to obtain oriented green compacts. The oriented

ceramics were obtained by sintering these green compacts without magnetic field. The sintered sample was cut into chips with different orientation directions, an

dielectric, piezoelectric, and pyroelectric properties were measured by impedance analyzer as a function of orientation direction. The electromechanical coefficient and piezoelectric constant

wed strong dependence on the orientation direction, and they were maximized perpendicular to the driving electric field and vibration direction, as shownThe maximum value of electromechanical coefficient was 24% higher than

The dependence of electromechanical coefficient k31 on the orientation direction

in direction was also analyzed, it could be approximated by a . We will discuss in the presentation the contribution of orientation

the piezoelectric properties.

Appl. Phys. Express, 8, 041501 (2015)IEEE Trans. Ultrason. Ferroelectr. Freq. Control,

0

0.1

0.2

0.3

0.4

0.5

0.6

0 10 20 30 40 50 60 70 80 90 Nonoriented

θ [degree]

Nb2/3)O3-Pb(Zr,Ti)O3

and their dependence on the orientation direction

Kawada1

chome, Nagaokakyo, Kyoto, JapanLausanne, Switzerland

well known for their high such as actuators and sensors.

piezoelectric constant are required s such as energy harvesting.

through ceramics with oriented grains. nd can be improved in a

kinds of orientation methods are studied.We employed a magnetic alignment method to fabricate oriented PNN-PZT ceramic[1]. The

PZT powder, water, and dispersant, was cast oriented green compacts. The oriented

ceramics were obtained by sintering these green compacts without magnetic field. into chips with different orientation directions, and their

dielectric, piezoelectric, and pyroelectric properties were measured by impedance analyzer as a electromechanical coefficient and piezoelectric constant

wed strong dependence on the orientation direction, and they were maximized at angle 90°as shown for k31 in Figure 1.

than that of non-oriented

on the orientation direction

could be approximated by a von the contribution of orientation

, 53, 1239 (2006)

Non-oriented

Field-Induced Phase Changes in Multi-Layer Piezoelectric Actuators during Electrical and Mechanical Load

Giovanni Esteves1, Chris M. Fancher1, Sören Röhrig2, Günther Maier2, Marco Deluca2,*, and Jacob L. Jones1

1Department of Materials Science and Engineering, North Carolina State University, 911 Partners Way, Raleigh, U.S.A.

2Department of Materials for Microelectronics, Materials Center Leoben Forschung GmbH, Kerpelystraße 2, Leoben, Austria

*Corresponding Author: marco.deluca@mcl.at Multilayer piezoelectric actuators (MPA(s)) with interdigitated metallic electrodes are

widely used in fuel injection systems for vehicle combustion engines due to their fast and reliable response. To develop the next generation of MPAs requires knowledge of the structure property relationships to optimize their performance. Mechanical constraints are known to alter the performance of MPAs. In fact, compressing an MPA (~ 50-60 MPa), leads to enhanced field-induced strain. [1] Previous studies on bulk ferroelectrics with simultaneous electrical and mechanical loading have been limited to the measurement of macroscopic properties. [1–3] Therefore, the local-scale mechanisms that enable the enhancement in macroscopic responses under low compression are inferred instead of directly verified.

In the present work, synchronized X-ray diffraction (XRD) and macroscopic property measurements were used to study the effect of electrical and mechanical loading in situ on MPAs. Rietveld refinement was performed on the measured diffraction data using a mixed phase model of tetragonal, P4mm, and rhombohedral, R3m. Refinement results suggest that a combination of phase fraction changes and domain reorientation is responsible for the enhanced response of MPAs during electric field cycling and low mechanical loads. Phase fraction versus electric field for various mechanical loads are reported. Under low compression loads, < 30 MPa, and high electric fields, the rhombohedral phase is the dominant phase while the opposite holds true for high loads, >100 MPa. The phase reversibility of the electric field-induced phase change increases with increasing mechanical load up to 70 MPa. The largest changes in the measured macroscopic strain and polarization were seen between 50-70 MPa, which correlate with the increased reversibility seen from the refinement results. Under high loads, >100 MPa, field-induced phase transitions and domain switching are significantly reduced. The suppression of both mechanisms is attributed to the large energy barrier that is imposed by the mechanical load on the MPA. When examining the dependence of purely mechanical loading, the tetragonal phase is the dominant phase and mainly changes in domain texturing are seen as opposed to mechanical load induced phase changes. Overall, the present XRD results, coupled with macroscopic measurements, suggest that interphase boundary motion plays a more substantial role in the enhanced response than domain reorientation. This work establishes new structure-property relationships for MPAs.

References [1] P. M. Chaplya and G. P. Carman, J. Appl. Phys. 90, 5278 (2001) [2] H. Grünbichler et. al., J. Eur. Ceram. Soc. 30, 249 (2010) [3] D. Zhou, M. Kamlah, and D. Munz, J. Mater. Res. 19, 834 (2004)

Figure 1. Tetragonal phase fraction versus electric field for 3 mechanical loads; 2 MPa, 70 MPa, and 300 MPa. The shaded regions indicate the error of the reported values (solid line).

Domain switching in multiferroic Bi0.9La0.1FeO3 thin films by Scanning Probe Microscopy

T.T. Jia1,*, H. Kimura1,*, Z.X. Cheng2, H.Y. Zhao3

1National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki, Japan. 2Institute for Superconducting and Electronic Materials, University of Wollongong, Squires

Way, North Wollongong, NSW, Australia. 3Department of Materials Science and Engineering, Wuhan Institute of Technology, No. 693

Xiongchu Road, Wuhan, China

*Corresponding Author: jia.tingting@nims.go.jp (T.T. Jia) or KIMURA.Hideo@nims.go.jp (H.

Kimura)

Multiferroic materials have been drawing extensive attention worldwide because they simultaneously possess ferroelectric, ferromagnetic, and/or ferroelastic properties. The coupling between these properties enables the dynamic manipulation of one ordering parameter by another, which is promising for broad applications in sensing, actuation, memory, etc.[1, 2] Numerous efforts have been made to investigate the coupling phenomena, especially the coupling between electric and magnetic orderings that would account for the magnetoelectric (ME) effect in multiferroic materials, due to the rich fundamental physics and exciting application potential in multiply controlled devices. [3] BiFeO3 has been one of the most popular materials in multiferroic research field, not only because of its simultaneous ferroelectricity and antiferromagnetism at room temperature, but also for the intrinsic ME coupling at room temperature. [4,5] In this work, we have successfully visualized the switching of both ferroelectric and magnetic domains in Bi0.9La0.1FeO3 thin film by electrical field using a SPM system. The Bi0.9La0.1FeO3 thin film was deposited on Pt/TiO2/SiO2/Si substrates using a pulsed laser deposition (PLD) system with the laser source at 355nm and a repetition rate of 10Hz. The film shows good ferroelectric and antiferromagnetic properties. Piezoresponse force microscopy (PFM) image and magnetic force microscopy (MFM) phase image show both ferroelectric and magnetic domain switching pattern which was written by the electric field. We have directly imaged the domain wall nucleation by applying an external electric field. Our results directly confirmed the existence of room temperature ME coupling in Bi0.9La0.1FeO3, which is potentially useful for the computing applications.

KEYWORDS: scanning probe microscopy, multiferroics, pulse laser deposition.

References [1] W. Eerenstein, N. D. Mathur, J. F. Scott, Nature, 442, 759(2006). [2] S.W. Cheong, M. Mostovoy, Nat. Mater., 6, 13(2007). [3] N. A. Spaldin, M. Fiebig, Science, 309, 391(2005).

[4] J. Wang, J. B. Neaton, H. Zheng et al., Science,299, 1719 (2003). [5] Y.-C. Chen, Q. He, F.-N. Chu, et al., Adv. Mater., 24, 3070 (2012).

Giant Photostriction in MAPbI3 and Ferroelectric Photovoltaic Effect

Lu You 1, Fan Zheng2, Andrew M. Rappe2, Liang Fang3, Junling Wang1,*

1 School of Materials Science and Engineering Nanyang Technological University, Singapore, 639798

Tel: +65 63168920 Fax: +65 67909081 2The Makineni Theoretical Laboratories, Department of Chemistry, University of Pennsylvania,

Philadelphia, Pennsylvania 19104−6323, United States 3Jiangsu Key Laboratory of Thin Films and Department of Physics, Soochow University, Suzhou

215006, People's Republic of China * Corresponding Author: jlwang@ntu.edu.sg

The past few years witnessed the explosion of research on photovoltaic cells based on the hybrid lead halide perovskites, in particular CH3NH3PbI3. Within a short period of 5 years, the efficiency of these cells has increased from 3.8% to over 20%. Despite the tremendous progress in device performance, much less is known about the underlying mechanism except that the carrier lifetime and diffusion length are astonishingly long in both thin films and single crystals. We recently observed a giant photostrictive response, i.e., light-induced dimension change, of more than 1200 ppm in CH3NH3PbI3. This is very similar to what has been observed in conventional ferroelectric oxides. However, the hybrid lead halide perovskites are not ferroelectric despite the large dipole of the CH3NH3 group. On the other hand, in conventional oxide perovskite BiFeO3 with strong ferroelectricity, we observed that the photovoltaic response could be significantly improved by destabilizing the polarization. Combining these observations, we propose a model to explain the photostriction of CH3NH3PbI3, and suggest a strategy to improve the photovoltaic property of conventonal ferroelectric materials. Reference: [1], “Giant Photostriction in Organic-Inorganic Lead Halide Perovskites”, Yang Zhou†, Lu You†, Zhiliang Ku, Hongjin Fan, Shiwei Wang, Daniel Schmidt, Andrivo Rusydi, Lei Chang, Le Wang, Peng Ren, Liufang Chen, Guoliang Yuan, and Junling Wang*, Nature Communications 7:11193, doi: 10.1038/ncomms11193, (2016). [2], “Polar-instability and/or indirect band gap driven photovoltaic enhancement: An insight from ferroelectric perovskite solar cells”, Lu You, Fan Zheng, Liang Fang, Yang Zhou, Liang Z. Tan, Zeyu Zhang, Guohong Ma, Daniel Schmidt, Andrivo Rusydi, Le Wang, Peng Ren, Shiwei Wang, Lei Chang, Andrew M. Rappe, Junling Wang, submitted (2016).

PTC properties of PE/CB composites for energy saving heating

elements

Ju-Hyun Yoo1a,Jong-Dae Han1, Ho-Jun Yoo2, Sung-Gyeong Ok3, Jong-Seok Ok4

1Department of electrical Engineering, Semyung University 2Jecheon High School

3C n T E S 4Department of English, Semyung University

*Corresponding Author: juhyun57@semyung.ac.kr

Polyethylene/Carbon black(PE/CB) composites have been widely used in various

application devices such as heating element, temperature sensor and current limiter due to its

Positive Temperature Coefficient(PTC) effect. It is well known that the PTC effect is

generated owing to a great thermal expansion caused as the result of dissolution of the

crystal. In this study, in order to develop the excellent energy saving heating elements, we

manufactured PE/CB composites. We systematically investigated the PTC properties of

PE/CB composites. The SEM results show that CB element homogeneously diffuses into PE.

The resistivity jump characteristics (ρmax/ρmin ) and temperature coefficient of resistivity(α)

of Bi(NaBa)TiO3 ceramics were better than those of PE/CB composites. However, PE/CB

composite was suitable for energy saving heating element application because the PE/CB

composites showed proper PTC properties.

References

[1] Y. Oh, S. Choi, and J. Yoo, J. KIEEME, 24, 559 (2011)

[2] Ki. Lee thesis. Junbuk university, (2008)

[3] Y. Park, S. Nahm, Y. Lee, Y. Jeong, J. Paik, D. Kim, and W. Lee, J. KIEEME, 21, 638

(2008)

Aurivillius phase Bi4Ti3O12-nBiFeO3 (n = 1-5) single crystals from melt H. Kimura1*, T.T. JIa1, R. Tanahashi1, and H.Y. Zhao2

1National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki, 305-0047, Japan 2Department of Materials Science and Engineering, Wuhan Institute of Technology

No. 693 Xiongchu dajia, Wuhan 430073, China *Corresponding Author: kimura.hideo@nims.go.jp

Aurivillius phase bismuth layer-structured materials with the formula of (Bi2O2)2+(Am-1

BmO3m+1)2- are expected an amazing variety of both structural and physical properties by changing the A and B cations as well as the number of perovskite-like units (m) [1-5].

In recent years, number of paper is increased on those Aurivillius compounds with m=4, 5 or more complicated one. In recent years, energy harvesting is of interest. One of the applications of piezoelectric materials is in-situ energy harvesting using piezoelectric effects by vibration, despite of low energy. Aurivillius compounds are expected to be new lead free piezoelectric materials for this application.

In this paper, we report the crystal growth (Fig. 1) and properties of these oxides compound; Bi5Ti3FeO15 (BTFO) (m=4); i.e., Bi4Ti3O12-nBiFeO3 (n= 1-5; n=1: BTFO-15, n=2: BTFO-18, n=3: BTFO-21, n=5: BTFO-27), compared with ceramics. BTFO-15 crystallizes in the polar space group A21am at room temperature. However, the structure of Bi4Ti3O12- nBiFeO3 (n= 2-5) compounds is not so clear yet. In these cases, smaller Fe ions are also incorporated into B sites with Ti ions, which may cause new magnetically ordered structures. Crystal growth direction is estimated along <110>. For the characterization, it is measured melting point, piezoelectric constant (d33), hardness and elastic modulus, and Polarization-Electric field relationship (P-E loop) along <110> and <001> directions. Since an anisotropy is expected in single crystals, electric properties of single crystals are measured along growth direction and its perpendicular direction.

Part of this work was supported by a Green Network of Excellence (GRENE) project of the

Ministry of Education, Culture, Sports, Science and Technology (MEXT) of Japan. The authors also acknowledge Prof. Ikuhara, Prof. Shibata, Dr. Matsumoto and Mrs. M. Nakabayashi of The University of Tokyo at GRENE for Transmission Electron Microscope (TEM) observations.

References [1] B. Aurivillius, Ark. Kemi 1, 463-480 (1950). [2] Y. Noguchi, M. Miyayama, T. Kudo, Phys. Rev. B 63, 214102 (2001). [3] C. M. Wang, J. F. Wang, Appl. Phys. Lett. 89, 202905, (2006). [4] Y. Noguchi, K. Murata, M. Miyayama, Ferroelectrics 355, 55-60, (2007). [5] Y. Noguchi, M. Miyayama, T. Kudo, Appl. Phys. Lett. 77, 3639-3641, (2000).

Fig. 1 Growing BTFO-15 crystal.

Domain engineering and Polarization Rotation in Ferroelectric Tricolor Superlattices

N. Lemée,1,* I. C. Infante,2 C. Hubault,1 A. Boulle,3 N. Blanc,4,5 N. Boudet,4,5

V. Demange,6 and M. G. Karkut1 1LPMC, EA 2081, Université de Picardie Jules Verne, 80039 Amiens, France

2 SPMS, UMR 8580 CNRS/CentraleSupélec, 92295 Châtenay-Malabry Cedex, France 3SPCTS, CNRS UMR 7315, Centre Européen de la Céramique, 87068 Limoges, France

4Université Grenoble Alpes, Institut Néel, F-38000 Grenoble, 5CNRS, Institut Néel, F-38042 Grenoble, France

6 ISCR, UMR 6226 CNRS/Université de Rennes 1, 35042 Rennes, France *Corresponding Author: nathalie.lemee@u-picardie.fr

Ferroelectric/paraelectric superlattices offer an excellent means for studying

ferroelectricity at the nanoscale. We have investigated tricolor superlattices based on two ferroelectrics (PbTiO3, PbZr0.2Ti0.8O3) and paraelectric SrTiO3

1. In this original geometry with 4 layer periodicity, an ultrathin SrTiO3 layer modifies the electrostatic boundary conditions between the ferroelectric layers and produces a depolarization field, which induces 180° stripe nanodomains. Combined with the electrostatic effect, there is competition between different polarization orientations via different strain states in the ferroelectric layers. Indeed we determine that PbZr0.2Ti0.8O3 layers are compressively strained whereas the PbTiO3 and SrTiO3 layers are under tensile strain. This leads respectively to an out-of-plane polarization and an in-plane polarization in these layers. This competition results in an overall polarization rotation in the nanodomains which we evidence by grazing incidence x-ray measurements. We demonstrate that this polarization rotation is associated to a monoclinic Mc phase as revealed by the splitting of the (HHL) and (H0L) reciprocal lattice points.

Figure 1. Out of plane (a) and in plane (b) XRD reciprocal space maps: the arrows indicate the satellite peaks, due to polar nanodomains in a tricolor superlattice.

The ferroelectric/paraelectric tricolor superlattices offer an effective pathway to stabilize

a rotation of the polarization compatible with an enhancement of the piezoelectric properties. Furthermore, these tricolor systems provide a way to engineer the domain structure and the domain size, by adjusting the thickness of the ferroelectric layers. Our work demonstrates that these tricolor superlattices constitute a tunable system to investigate the concomitant effects of strains and depolarizing fields.

References [1] N. Lemee et al., ACS Appl. Mater. Interfaces, 7, 19906 (2015).

Homogenization and Characterization of Piezoelectric Stack Actuators by Means of the Inverse Method

M. Weiß,* S. J. Rupitsch, and R. Lerch

Chair of Sensor Technology, FAU Erlangen-Nürnberg, Paul-Gordan-Str. 3/5, Erlangen, Germany

*Corresponding Author: manuel.weiss@fau.de Piezoelectric stack actuators are utilized in a wide field of application due to their relatively

high mechanical displacements and forces. Numerical simulations are suitable to predict the mechanical and electrical performance of such transducers in advance. The major conditions for reliable numerical simulations are, however, a detailed knowledge regarding internal structure of the transducer as well as precise material parameters of all involved materials. Especially stack actuators exhibit a complex composition and a large number of used materials (e.g., piezoceramics, adhesives, electrodes, passive discs). These are the reasons why the preparatory work of numerical simulations is very challenging and elaborate.

In this contribution, we present an innovative and novel top-down approach, which simplifies the actuator structure by means of a homogenized, uniform model for only one fictive piezoelectric material with effective parameters (see Fig. 1). These effective material parameters are determined through the inverse method, a simulation-based approach for identifying all small signal parameters of piezoelectric materials [1, 2]. In doing so, frequency-resolved electrical impedance and mechanical displacement measurements of the piezoelectric actuator serve as input quantities. Figure 2 displays exemplary characterization results: Simulations of frequency-resolved electrical impedance and mechanical displacement (excitation voltage uത ( f ) = 1 V) for the identified effective parameters coincide well with measurements.

Figure 1. Schematic of complex and homogenized stack actuators

Figure 2. Exemplary results for stack actuator P-010.20P (Physik Instrumente)

We will illustrate the principle of the homogenization based on the inverse method, the

measurement setups and effective material parameters of commercially available stack actuators. Moreover, we point out advantages (e.g., efficient and precise numerical simulations, easy implementation), challenges (e.g., initial guess) as well as limitations (e.g., permissible frequency range, mechanical conditions) of our approach.

References [1] S.J. Rupitsch, J. Ilg, IEEE Transactions on UFFC, 62, 1403-1413 (2015) [2] S.J. Rupitsch et al., Procedia Engineering, 25, 1441-1444 (2011)

Relaxor Ferroelectricity and Field Induced Phase Transformation in the Lead-

Free Piezoelectric (Ba0.85 Ca0.15)(Ti0.90 Zr0.10)O3 Rajeev Ranjan* and Kumar Brajesh

Department of Materials Engineering, Indian Institute of Science, Bengaluru-560012, India *Corresponding Author: rajeev@materials.iisc.ernet.in

The lead-free ferroelectric alloy (Ba0.85 Ca0.15)(Ti0.90 Zr0.10)O3 (15/10BCZT ) is well known for its exceptionally large piezoelectric response (d33 ~ 600 pC/N) [1]. We have investigated the mechanism(s) associated with the anomalously large piezoelectric response of this piezoceramic by temperature and electric field dependent dielectric and structural study. A detailed structural analysis of the x-ray powder diffraction pattern at room temperature revealed signatures of three phase coexistence: tetragonal (P4mm), rhombohedral (R3m) and orthorhombic (Amm2). On application of electric field, the fractions of the orthorhombic and the rhombohedral phases increase, suggesting a field induced P4mm to Amm2 + R3m transformation.

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Temperature dependent dielectric study shows that the system exhibits a weak dielectric relaxation near the anomaly temperature. The dielectric dispersion vanishes above ~ 200 oC (Fig. 1). Deviation from Curie-Weiss behavior and excess thermal expansion also sets in below this temperature. These results suggest that polar nano regions, characteristic of a relaxor ferroelectric material, appear deep in the cubic region. The dielectric anomaly therefore appears to be a manifestation of relaxor to normal ferroelectric transformation, instead of a normal paraelectric-ferroelectric thermodynamic transformation. Our results provide new insight with regard to the anomalous piezoelectric response of this lead-free system.

References [1] W. Liu and X. Ren, Phys. Rev. Lett. 103, 257602 (2009)

In-situ Electric Field Dependent High Energy x-Ray Diffraction Close to the

Morphortropic Phase Boundary of PbTiO3-BiScO3 Dipak Kumar Khatua1, Lalitha K V1, Chris M. Fancher2, Jacob L. Jones2, and Rajeev

Ranjan1*

1Department of Materials Engineering, Indian Institute of Science, Bengaluru 560012, India 2Department of Materials Science and Engineering, North Carolina State University, Raleigh,

NC 27695, USA *Corresponding Author: rajeev@materials.iisc.ernet.in

We have investigated the mechanism associated with the large piezoelectric response of the morphotropic phase boundary (MPB) composition of the piezoelectric system (1-x)PbTiO3-(x)BiScO3 by in-situ electric field dependent high energy synchrotron x-ray diffraction. A comparative study was undertaken on two close by composition x = 0.40 and x = 0.3725, corresponding to a non-MPB (rhombohedral phase) and the MPB (rhombohedral + tetragonal phases), respectively. Detailed analysis revealed that the non-MPB composition exhibits a considerably higher domain switching and lattice strain than the MPB composition. The MPB composition however exhibits an additional phenomenon of field induced rhombohedral to tetragonal transformation. Our results suggests that the significantly large piezoelectric response of the MPB composition as compared to the non-MPB composition is primarily due to the field induced phase transformation.

Polarization switching kinetics in PZT ceramics containing oriented anisotropic pores

R. Khachaturyan,1 S. Zhukov,1 J. Schultheiß,1 C. Galassi,2 C. Reimuth,1 J. Koruza,1 and Y.A. Genenko,1*

1Institut für Materialwissenschaft, Technische Universität Darmstadt, 64287 Darmstadt, Germany

2CNR-ISTEC National Research Council, Institute of Science and Technology for Ceramics, I-48018 Faenza (RA), Italy

* Y.A. Genenko: genenko@mm.tu-darmstadt.de

Electric-field-induced polarization reversal in ferroelectric ceramics can be considerably

accelerated by texturing of these materials1.This phenomenon can be explained within the frame of the Inhomogeneous Field Mechanism (IFM) model by variation of spatial distribution of the applied electric field in polycrystalline ferroelectrics2. Porous lead zirconate titanate (PZT) ceramics present a model material3, which allows controlling the field distributions by orientation of anisotropic pores. In this contribution, comprehensive experimental studies of PZT ceramics of different pore morphologies and orientation grade are supported by extensive finite-element (FEM) simulations of field distributions and the IFM model analysis of switching kinetics. Particularly, distributions of pore sizes are investigated by Scanning Electron Microscopy (SEM) and their effect on field distributions is simulated by FEM. The results are compared with the IFM analysis of polarization reversal data over a large time window, which delivers statistical distributions of local polarization switching times.

FEM simulations show that statistical field distributions are virtually independent of the individual pore size when the total porosity is fixed. This applies also to different size distributions of round pores and to anisotropic (elliptical) pores. On the other hand, orientation of elliptical pores with respect to the applied external field direction has a significant effect on local field distributions. Increasing porosity leads in all cases to broadening of field distributions, which can be explained by scaling analysis; a result qualitatively supported by experiment.

References [1] S. Zhukov, Y.A. Genenko, J. Koruza, J. Schultheiß, H. von Seggern, W. Sakamoto, H. Ichikawa, T. Murata, K. Hayashi, and T. Yogo, Appl. Phys. Lett. 108, 012907 (2016). [2] Y.A. Genenko, S. Zhukov, S.V. Yampolskii, J. Schütrumpf, R. Dittmer, W. Jo, H. Kungl, M. J. Hoffmann, and H. von Seggern, Adv. Funct. Mater. 22, 2058 (2012). [3] C. Galassi, J. Eur. Ceram. Soc. 26, 2951 (2006).

Investigation of the photovoltaic effect in BiFeO3 thin films S. Yousfi1, B. Carcan1, F. Le Marrec1, H. Bouyanfif1, M. El Marssi1, S. Matzen2

1LPMC EA2081, Université de Picardie Jules Verne 33 Rue Saint Leu, 80000 Amiens, France 2Institut d’Electronique Fondamentale, Université Paris Sud, F91405 Orsay cedex

During the last years, multiferroic materials have gained great attention due to their

fundamental physics and possible integration in advanced application. BiFeO3 (BFO) appears actually as one of the most interesting, because it shows multiferroic properties at room temperature. Recently a peculiar photovoltaic effect has also been revealed in BFO with a large open circuit voltage Voc above the band gap. The very large Voc (up to 16V) was first interpreted as arising from the domain structure and electric field at the domain walls. More recently an interpretation based on the symmetry was put forward to explain the anomalous high Voc. In both cases planar geometry of the PV effect was used and the ferroelectric polarization is responsible of the electric field separating the electrons from the holes in the thin films. A smaller Voc (<1V) was however measured in parallel plate capacitor and the origin of this low PV response may be obscured by the possible existence of a Schottky barrier, defects, depolarizing field and the complex rhombohedral ferroelectric domain structure. To better understand the observed PV effect, we have grown by pulsed laser deposition BFO thin films with different thickness on buffered LaAlO3 substrates. A 20nm thick SrRuO3 layer is used as a bottom electrode while Pt and ITO top electrodes were deposited. Reciprocal space mappings and Raman spectroscopy were used to characterize the domain structure and symmetry. Ferroelectric properties were investigated using a Sawyer-Tower home made system and piezo-force microscopy. Very large spontaneous polarization were measured and I(V) curves were collected at different temperatures to understand the transport properties (interface or bulk limited and the existence of a Schottky barrier). PV effects under laser illumination of different wavelength (from 647nm to 457nm) and powers were investigated at different temperatures. Observed switchable Voc and Isc (short circuit current) will be presented showing that the PV effect arises from the ferroelectric field effect. An attempt to fully understand the electric structure of the BFO films has been performed and an impedance spectroscopy investigation of the ferroelectric PV solar cell will be also presented.

Mechanically induced ferroelectric long range order in relaxor ferroelectrics B. Kaeswurm,1,* and F.H. Schader,2 K.G. Webber,1

1Friedrich Alexander Universität Erlangen, Erlangen, Germany 2Technische Universität Darmstadt, Darmstadt, Germany

*Corresponding Author: Barbara.Kaeswurm@fau.de Mechanical stress can lead to a transition from a relaxor ferroelectric state to a long-range

ferroelectric order. Analogous to the well-known electrical case, [1-3] it has been shown that an anomaly in the temperature dependent dielectric response occurs in mechanically textured lead-free relaxors ((Na1/2Bi1/2)TiO3-0.06BaTiO3) [4]. Figure 1a) shows the relative permittivity as a function of temperature at different frequencies for unpoled polycrystalline NBT-0.06BT between 300 K and 650 K. The same data is displayed in dotted lines in panels b) and c) for comparison. The measured dielectric response is characteristic of NBT-based ferroelectric materials. After poling with an electric field of 2 kV/mm at 423 K for 5 min (field-cooled), an anomaly in the relative permittivity is observed at 350 K (Fig. 1b)), consistent with previous studies. This is due to a ferroelectric-relaxor transition occurring at temperature TF-R. In comparison, a sample mechanically textured at 423 K with a compressive stress of –500 MPa for 5 minutes (field-cooled) shows an almost identical temperature dependent dielectric anomaly. This clearly demonstrates that an external uniaxial mechanical stress induces a long-range ferroelectric order in relaxor ferroelectrics.

Figure 1: Temperature-dependent real part relative permittivity of polycrystalline NBT-0.06BT a) unpoled , b) electrically poled and c) mechanically textured [4].

The aim of this work is to show the influence of stress on the relaxor to ferroelectric

transition in lead free and lead containing model systems. Temperature and load dependent measurements of the longitudinal piezoelectric coefficient d33 are presented. The dielectric and piezoelectric properties will be discussed in the context of a stress-temperature phase diagram.

References [1] R. Sonmer and N.K. Yushin, J.J. van der Klink, Phys. Rev. B, 48, 13230(1993) [2] V. Bobnar, Z. Kutnjak, R.Pirc and A. Levstik, Phys. Rev. B, 60, 6420(1999) [3] J. E. Daniels, W. Jo, J. Rödel, and J. L. Jones, Appl. Phys. Lett. 95, 032904 (2009) [4] F.H. Schader, Z. Wang, M. Hinterstein, J. E. Daniels, K.G. Webber, Phys. Rev. B, in press (2016)

Processing and characterization of transparent piezoelectric thin films on glass substrates for large area transducers

D. Sette, N. Adjeroud, S. Girod, R. Leturcq, and E. Defay*

Department of Materials Research and Technology, Luxembourg Institute of Science and Technology - LIST,

Rue du Brill, L-4422 Belvaux, Luxembourg *Corresponding author: emmanuel.defay@list.lu

The field of micro-electromechanical system (MEMS) has largely driven the development of processing techniques of piezoelectric thin films. In particular, sputtering and chemical solution deposition (CSD) have reached industrial maturity and are now integrated with silicon technologies. In this context, it is worth adapting these techniques to other substrates for innovative applications. In this study, the fabrication of lead zirconate titanate (PZT) on glass substrates together with transparent electrodes is investigated for large area applications, such as acoustic transducers or haptic actuators.

Pb(Zr0.52Ti0.48)O3 thin films are grown following a sol-gel route on fused silica wafers where a nucleation layer has been previously deposited. 200 nm to 1 µm-thick PZT layers are realized, showing excellent perovskite crystallization (Fig. 1.a). Different materials are tested for the electrodes, namely evaporated platinum, gold, and ALD aluminum-doped zinc oxide (Fig. 1.b).

Absorbance measurements of 200 nm-thick PZT layers on glass exhibit transmittance higher than 60% in the visible range. When patterned with 100 nm-thick platinum electrodes, PZT dielectric constant value is εPZT = 1290 with a tuning ratio of 43% at 500kV/cm. The d33 piezoelectric coefficient is in the range of 100 pm/V, as fitted from displacement measurements on a cantilever-like structure. To achieve transparent transducers, a trade-off between electrodes transparency and electrical conductivity is necessary (material and thickness). Absorbance measurements, electrical and piezoelectric properties of devices with different electrodes configurations will be exposed during the conference.

Figure 1.a) 200nm-thick PZT diffraction diagram on fused silica. b) Fused silica substrate with 20 nm-thick nucleation layer, 200 nm-thick crystallized PZT,

and 100 nm-thick patterned Al-doped ZnO electrodes.

Acknowledgments We are indebted with Gwenael Le Rhun for having provided commercial sol-gel precursors and Nohora Caicedo for electrodes design.

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The appearance of ferroelectricity and weak ferromagnetism of hexagonal stabilized ErFeO3 thin film

H. Yokota,1,* T. Nozue,1 S. Jitsukawa,1 S. Nakamura2,3 Y. Kobayashi4, S. Kitao4 and M. Seto4

1Dept. of Phys., Chiba Univ., 1-33 Yayoi-cho, Chiba, JAPAN 2Dept. of Sci. and Eng., Teikyo Univ., 1-1 Toyosatodai, Tochigi, JAPAN

3Adv. Research Center of Sci. and Eng., Waseda Univ., 3-4-1 Okubo, Tokyo, JAPAN 4 Research Reactor Institute, Kyoto Univ., 2 Kumatori, Kyoto, JAPAN

*Corresponding Author: hiroko.9bq@chiba-u.jp

Hexagonal ReFeO3 (Re: rare earth) system has been a recent subject of increased interest because of its multiferroic property. We fabricated hexagonal ErFeO3 (h-ErFeO3) thin films by a pulsed laser deposition method and the c axis oriented h-ErFeO3 thin film was obtained on YSZ (111) and/or Al2O3 (0001) substrate. To examine the ferroelectricity, DE hysteresis, dielectric constant, and superlattice measurements were carried out. These results indicated that h-ErFeO3 thin film exhibits ferroelectricity at room temperature.[1,2] Magnetic properties were investigated by a magnetic property measurement system (MPMS) and 57Fe Mössbauer spectroscopy. Below 120 K, a weak ferromagnetism appears along the c axis and MH hysteresis appears at this temperature range.[1]

To understand the magnetic structure of Fe ion, we performed Mössbauer spectroscopy under the application of a magnetic field. 57Fe-enrich ErFeO3 thin film fabricated on Al2O3 (0001) substrate was used as a specimen. Mössbauer spectrum was measured in a transmission geometry using a 57Co-in Rh as the J-ray source. The incident direction of J-ray was parallel to the c axis of the specimen within an error of ±2º. The experiment was conducted at 4.2 K and a magnetic field of 5 T was applied parallel to the c axis. Figure 1(a) shows the Mössbauer spectrum measured at 4.2 K under a magnetic field. For a comparison, a Mössbauer spectrum without a magnetic field is also shown in Fig. 1 (b). Magnetically ordered profiles are obtained for both spectra. The best fit was obtained assuming that h-ErFeO3 thin film possesses up- and down- domain structures. The existence of different domains can explain the disappearance of MH hysteresis loop observed below 30 K. With decreasing temperature, the magnetic anisotropy increases and it prevent the domain motion along the applied magnetic field. It is worth noticing that the quadrupole coupling constant increases around 12 % with the magnetic field and it would correspond to the multiferroic property.

References [1] H. Yokota, T. Nozue, S. Nakamura, H. Hojo, M. Fukunaga, P.-E. Janolin, J.-M. Kiat, and A. Fuwa, Physical Review B 92, 054101 (2015) [2] H. Yokota, T. Nozue, S. Nakamura, M. Fukunaga, and A. Fuwa, Japanese Journal of Applied Physics 54, 10NA10 (2015)

Figure 1 Mössbauer spectrum of h-ErFeO3 thin film at 4.2 K at applied magnetic field of (a) 5 T, and (b) 0T. Magnetic field was applied parallel to the c axis.

Nanoscaled Permittivity Distribution Imaging Using an SNDM Probe Y. Hiranaga,* N. Chinone, K. Hirose, and Y. Cho

Research Institute of Electrical Communication, Tohoku University 2-1-1 Katahira, Aoba-ku, Sendai, Japan

*Corresponding Author: hiranaga@riec.tohoku.ac.jp The importance of nanoscaled imaging or characterization of dielectric materials are

growing up with miniaturization and performance enhancement of dielectric devices. However permittivity measurements in nanoscaled region are often accompanied by difficulties due to the effect of stray capacitance. Scanning nonlinear dielectric microscopy (SNDM) is a technique which can detect capacitance variation with high sensitivity. Conventional SNDM has mainly been used for observation of local electrical anisotropies through nonlinear permittivity measurement. In this presentation, we will propose a novel method for linear permittivity imaging using SNDM.

The schematic diagram of the proposed method is shown in Fig. 1. This setup contains a probe composed of an LC resonant circuit and a conductive cantilever for capacitance imaging, as with a conventional SNDM. The distance between the cantilever tip and a sample surface is alternatingly modulated by a piezo vibrator. The capacitance variation induced by the cantilever vibration is dependent on the linear permittivity of the measurement sample. This capacitance variation is converted to the frequency shift of the LC resonant circuit, and is reproduced by an FM demodulator. Thus the intensity of demodulated signal corresponds to the linear permittivity of the sample. A cross section of a multilayer oxide film was observed for a demonstrative test. The result shown in Fig.2 verified that the proposed method can visualize linear permittivity in nanoscaled region.

Acknowledgments This work was supported in part by a Grant-in-Aid for Scientific Research (A) (16H02330) from the Japan Society for the Promotion of Science (JSPS). References [1] Y.Cho, Jpn. J. Appl. Phys., 46, 4428 (2007)

Figure 1. Schematic diagram of the proposed method for observing nanoscaled permittivity distribution using an SNDM probe.

Figure 2. Permittivity image of a TiO2/ZrO2/Al2O3 multilayer film observed by the proposed method.

Dielectric Spectroscopy and Magnetometry Investigation of Gd- and Dy-doped Strontium Titanate Ceramics

A. Tkach,1,* P. M. Vilarinho,1 J. S. Amaral,2,3 and V. S. Amaral2

1CICECO – Aveiro Institute of Materials, Department of Materials and Ceramic Engineering, University of Aveiro, Campus Universitario de Santiago, 3810-193 Aveiro, Portugal

2CICECO – Aveiro Institute of Materials, Department of Physics, University of Aveiro, Campus Universitario de Santiago, 3810-193 Aveiro, Portugal

3IFIMUP and IN – Institute of Nanoscience and Nanotechnology, Department of Physics and Astronomy, Faculty of Science of University of Porto,

R. do Campo Alegre, 687, 4169-007 Porto, Portugal *Corresponding Author: atkach@ua.pt

Doping of incipient ferroelectrics (IF) with magnetically active ions makes them attractive

for possible multiferroic functional applications, including multiple state memory elements, electric-field controlled ferromagnetic resonance devices, tunable microwave devices with constant characteristic impedance. Recently, dielectric and magnetic anomalies were found to be coupled in Sr1-xMnxTiO3 ceramics and thin films according to the so called “multiglass” scenario, where freezing of the electric dipoles, created by off-centre Mn2+

Sr ions in highly polarizable IF lattice of SrTiO3, initiates the transition of the magnetic Mn2+ spin moments into a spin glass state [1-3].

Figure 1. Real part of the dielectric permittivity, measured at 10 kHz, (right scale) and

magnetization, measured at 100 Oe after zero field cooling, (left scale) of Sr1-1.5xDyxTiO3 and Sr1-1.5xGdxTiO3 ceramics as a function of temperature

In this work, a systematic research on the structure, microstructure, dielectric and magnetic

behaviour of conventionally prepared SrTiO3 ceramics doped with such magnetically active ions as Dy3+ and Gd3+ is reported. The room-temperature crystallographic structure of the obtained Sr1-1.5xDyxTiO3 and Sr1-1.5xGdxTiO3 ceramics (x ≤ 0.05) is analysed by x-ray diffraction, while scanning electron microscopy together with energy dispersive spectroscopy is employed for microstructural and local chemical characterization. The dielectric spectroscopy and magnetometry measurements are performed in a temperature range from 2 to 300 K and discussed.

References [1] V. V. Shvartsman et al., Phys. Rev. Lett., 101, 165704 (2008) [2] A. Tkach et al., Ferroelectrics, 426, 274 (2012) [3] A. Tkach et al., Adv. Funct. Mater., 23, 2229 (2013)

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Local structure in sustainable functional ceramics

Ian M. Reaney

Material Science and Engineering

University of Sheffield, Sheffield, S1 3JD, UK

The local structure-property relations in sustainable functional ceramics have been elucidated using a combination of aberration corrected and conventional transmission electron microscopy. The complex nature of the phase transition sequence and cation ordering in RE-doped SrTiO3, a potential n-type thermoelectric materials, is elucidated and the relation to thermal and electrical conductivity established. The complex hierarchical structure of Na1/2Bi1/2TiO3 and related compounds is also presented with a view to understanding the extent of pseudosymmetry in this system and its role in associated ferroic transitions. Finally, comparison of bulk and thin film RE doped BiFeO3 is made to illustrate the role of substrate clamping on phase assemblage.

Ferroelectric Nanodomain Observation in Yttrium-Doped HfO2 Thin Films Using Scanning Nonlinear Dielectric Microscopy

Z. Chen,1 Y. Hiranaga, 1,* T. Shimizu,2 K. Katayama,3 T. Mimura,3 H. Funakubo,2,3 and Y. Cho1

1 Research Institute of Electrical Communication, Tohoku University 2-1-1 Katahira, Aoba-ku, Sendai, Japan

2 Materials Research Center for Element Strategy, Tokyo Institute of Technology 4259 Nagatsuta, Midrori-ku,Yokohama, Japan

3 Department of Innovative and Engineered Materials, Tokyo Institute of Technology 4259 Nagatsuta, Midrori-ku, Yokohama, Japan

*Corresponding Author: hiranaga@riec.tohoku.ac.jp Orthorhombic-phase HfO2 thin films are attracting considerable attention as novel

materials which possess excellent ferroelectric property with a thickness less than 20 nm. We studied on applicability of ferroelectric HfO2 films in recording media for ferroelectric probe data storage application based on scanning nonlinear dielectric microscopy (SNDM). Yttrium-doped HfO2 (Y:HfO2) films with a thickness of 11 nm were deposited on ITO/YSZ substrate using pulsed laser deposition method. The epitaxial growth of film was confirmed by the X-ray diffraction method. We revealed that SNDM can be used for observation of ferroelectric domain structures in HfO2–based films as shown in Fig.1. An SNDM image of nanodomain dot written on the Y:HfO2 film is shown in Fig.2. This result revealed that domain dot with a diameter of approximately 30 nm can be formed on the film.

Acknowledgments This work was supported in part by a Grant-in-Aid for Scientific Research (A) (16H02330) from the Japan Society for the Promotion of Science (JSPS). References [1] J. Müller et al., Nano Lett., 12, 4318 (2012) [2] T. Shimizu et al., Appl. Phys. Lett., 107, 032910 (2015)

Figure 1. SNDM image of a domain inversion pattern written on a Y:HfO2 film by applying a DC voltage

Figure 2. SNDM image of nanodomain dots written on a Y:HfO2 film by applying pulse voltages

Lead-free (K, Na)(Sb, Nb)O3-x(Bi, Na, K)ZrO3 Piezoelectric Thin Films Derived from Chemical Solution Deposition

Yumei Wang1,2,3, Xian Qin2, Meysam Sharifzadeh Mirshekarloo2, Kui Yao2*, Francis Eng Hock Tay1

1Department of Mechanical Engineering, National University of Singapore, 21 Lower Kent Ridge Road, Singapore.

2Institute of Materials Research and Engineering, 2 Fusionopolis Way, Innovis, #08-03, Singapore.

3NUS Graduate School for Integrative Sciences and Engineering, National University of Singapore, 28 Medical Drive, Singapore.

*Corresponding Author: k-yao@imre.a-star.edu.sg

(K, Na)NbO3 (KNN)-based lead-free piezoelectric ceramic materials have received intensive attention to replace currently market-dominating lead-based piezoelectric compositions for various electromechanical sensors and transducers applications, with serious concern of lead hazard to environment and human health. However, it is still challenging to obtain competitive piezoelectric performance properties in KNN-based thin films. Here we report lead-free (K, Na)(Sb, Nb)O3-x(Bi, Na, K)ZrO3 ferroelectric thin films derived from a chemical solution deposition method modified with appropriate stabilizing chemical agents. Orthorhombic-rhombohedral-tetragonal phase transition was observed with a composition of 0.01 <x< 0.07. An effective large piezoelectric coefficient d33 up to 124.8 pm/V was obtained in the thin film with a selected composition, under the substrate clamping condition. This value is comparable to those of optimized Pb(Zr,Ti)O3 (PZT)-based thin films under similar testing condition. In addition, Density Function Theory (DFT)-based first principles calculation was conducted to study the energetically preferred phase of (K, Na)(Sb, Nb)O3-x(Bi, Na, K)ZrO3 with varied composition. The theoretical calculation indicates a phase transition trend consistent with the experimental observations, with x increasing from 0.01 to 0.07. The results here show that the (K, Na)(Sb, Nb)O3-x(Bi, Na, K)ZrO3 lead-free piezoelectric thin film derived from our chemical solution approach is a very promising alternative material to PZT-based thin films.

Ultra-Low Temperature Epitaxial Growth of Spinel Ferrite Films by High-Pressure Sputtering

R. Y. Zhang,1 M. Liu,1 L. Lu,1 S. B. Mi,2and W. Hong1,2* 1Advanced Microelectronic Material Research Laboratory, Xi’an Jiaotong University, No.28

Xianning West Road, Xi’an City, China 2 State Key Laboratory for Mechanical Behavior of Materials, Xi’an Jiaotong University, No.28

Xianning West Road, Xi’an City, China *Corresponding Author: hwang@xjtu.edu.cn

Spinel ferrites play important roles in microwave device, heterogeneous catalysts, sensors,

and spintronic applications. The trend of developing microelectronic devices with high integration density, high operating frequency, and multi-functionalities drives the demand of direct integration of ferrite passive devices with semiconductors, organic electronic, flexible electronics. However, the high processing temperature of spinel ferrites using traditional synthesis techniques would significantly deteriorate the performance of above mentioned devices, which can’t sustain high temperature. By using high-pressure sputtering technique, nanoscale control of microstructure enables epitaxial growth of lithium ferrite thin films with high crystalline quality at ultra-low temperature of 200 ℃. This temperature of 200 ℃ is even better than the best record of 250 ℃ by using atomic layer deposition reported in the literature. More importantly, the sputtering technique is better recognized by industries and more suitable for massive production than any other techniques. Furthermore, the measured magnetization of 145 emu/cc and good ferromagnetic resonance properties at 9.5GHz are feasible for its wide applications in above mentioned devices.

Figure 1. TEM images of 200 ℃ prepared LFO epitaxial films with high crystalline quality

and feasible magnetic properties The influence of growth temperature on magnetic properties is also systematically studied. It

is indicated magnetization, coercivity, FMR linewidth and resonance field are decides by microstructures (crystalline qualities, defect, and epitaxial strain) of films, which depend on the growth temperature. By preparing spinel ferrite epitaxial films at fixed growth temperature with different thicknesses, the magnetic properties are tuned by gradually relaxed epitaxial strain with increasing film thickness, demonstrating an easy way to control properties of epitaxial film through “size effect”.

References [1] R. Y. Zhang, M. Liu, L. Lu, S. B. Mi, H. Wang, CrstEngComm, 17, 8256 (2015) [2] R. Y. Zhang, M. Liu, L. Lu, S. B. Mi, H. Wang, J. Mater. Chem. C, 3, 5598 (2015)

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Tailoring the Electromechanical Properties of Lead-Free Ferroelectrics with the Ceramic/Ceramic Composite Approach

A. Ayrikyan,1,* L. Molina-Luna,2 M. Duerrschnabel,2 F. Weyland,2 S. Steiner,2 and K.G Webber1

1Department of Materials Science, Glass and Ceramics, Friedrich-Alexander Universität Erlangen-Nürnberg, Germany

2Institute of Materials Science, Technical University of Darmstadt, Germany *Corresponding Author: azatuhi.ayrikyan@fau.de

Ferroelectric materials are an important enabling technology for electromechanical actuators. There have been a number of promising materials for the replacement of lead-based ferroelectrics that are primarily based on (K,Na)NbO3 (KNN), BaTiO3 (BT), or (Bi0.5Na0.5)TiO3 (BNT). The BNT-based materials have shown exceptionally large unipolar strains. Unfortunately, this transition requires large electrical fields, typically in the range of 6-8 kV/mm [1]. Recently, ceramic/ceramic composite ferroelectrics have been proposed as a method of tailoring the electromechanical behavior in lead-free ferroelectrics [2][3].

Figure 1. Unipolar Strain and Polarization of 0-3 and 2-2 composites as a function of E-field.

In this study, the macroscopic electromechanical behavior of ceramic/ceramic lead-free ferroelectric 2-2 (multilayer) and 0-3 (mixed) composites was characterized at room temperature. Composites consisted of a nonergodic relaxor, (Bi1/2Na1/2)TiO3–0.07BaTiO3, with an irreversible electric-field-induced relaxor-to-ferroelectric transition, and an ergodic relaxor, Bi(Na0.25K0.75)TiO3–6BiAlO3, which undergoes a reversible electric-field-induced relaxor-to-ferroelectric transition. Microstructural investigations of the multilayer composites, including compositional analysis, porosity and grain size measurements, were performed and differences in these properties as a function of composition were observed. Results show that co-sintered multilayer structures display an enhancement in the unipolar strain during electric field loading. References [1] Z. Luo, T. Granzow, J. Glaum, W. Jo, J. Rödel, and M. Hoffman, “Effect of Ferroelectric Long-

Range Order on the Unipolar and Bipolar Electric Fatigue in Bi1/2Na1/2TiO3-Based Lead-Free Piezoceramics,” J. Am. Ceram. Soc., 94 (11) 3927–3933 (2011)

[2] D. Su Lee, S. Jong Jeong, M. Soo Kim, and J. Hyuk Koh, “Electric field induced polarization and strain of Bi-based ceramic composites,” J. Appl. Phys., 112(12) 124109 (2012)

[3] C. Groh, et al., “Relaxor/Ferroelectric Composites: A Solution in the Quest for Practically Viable Lead-Free Incipient Piezoceramics,” Adv. Funct. Mater., 24(3) 356–62 (2013)

Realization of face-shear (d36) mode in PZT ceramics via ferroelastic domain engineering and its applications in shear-horizontal wave excitation

H.C. Miao,1,* F.X. Li1 1College of Engineering, Peking University, Beijing, 100871, China

*Corresponding Author: chenhong_miao@pku.edu.cn The fundamental shear horizontal (SH0) wave in plate-like structures is extremely useful for

non-destructive testing (NDT) and structural health monitoring (SHM) as it is non-dispersive. However, currently the SH0 wave is usually excited by electromagnetic acoustic transducers (EMAT) whose energy conversion efficiency is fairly low. The face-shear (d36) mode piezoelectrics is more promising for SH0 wave excitation but this mode can only exist in single crystals of specific point groups and cut directions. Theoretically the d36 coefficient vanishes in piezoelectric ceramics because of its transversally isotropic symmetry. In this work, we modified the symmetry of poled PZT ceramics from transversally isotropic to orthogonal through ferroelastic domain switching by applying a high lateral stress along the “2” direction under elevated temperature (80°C for PZT-5H and 110°C for PZT-4) and holding the stress for several hours. After removing the compression, the piezoelectric coefficient d31 is found significantly larger than d32. Then by cutting the compressed sample along the 45° direction, we realized d36 coefficients up to 270 pC/N in PZT-5H ceramics and 108 pC/N in PZT-4 ceramics. We then successfully excite SH0 wave in the aluminum plate using a face-shear PZT-4 square patch and receive the wave using a face-shear PMN-PT patch. The frequency response and directionality of the excited SH0 wave were also investigated. The SH0 wave can be dominate over the Lamb waves (S0 and A0) from 160 kHz to 280 kHz. The wave amplitude reaches its maxima along the 0° and 90° directions, symmetric along the 45° direction. The amplitude can keep over 80% of the maxima when the deviate angle is less than 30°, while it vanishes quickly at the 45° direction. The excited SH0 wave using piezoelectric ceramics could be very promising in the fields of NDT and SHM.

Figure 1. (a) Measured impedance spectrum of a d36 type PZT-5H patch; (b) Simulated

deformation at resonance of the d36 mode by using finite element method.

References [1] H.C. Miao, F.X. Li*, Appl Phys Lett 107, 122902 (2015) [2] H.C. Miao, X. Chen, H.R. Cai, F.X. Li*, J. Appl Phys 118, 214102 (2015) [3] H.C. Miao, S.X. Dong, F.X. Li*, arXiv 1603.05077 (2016)

Understanding of origin of high piezoelectric properties of KNN-based

ceramics

Jiagang Wu, Jie Xing, Qian Gou, Zhi Tan, Laiming Jiang, Dingquan Xiao, and Jianguo Zhu*

College of Materials Science and Engineering, Sichuan University,

Wangjiang Road 29, Chengdu, 610064, China *E-mail: nic0400@scu.edu.cn

It is very important to understand the physical origin of high piezoelectricity in order to

investigate the relationships between the phase boundaries, phase compositions, and piezoelectric properties of KNN materials. In recently years, the environmental friendly lead-free piezoelectric ceramics are investigated for the purpose of replacing the widely used Pb(Zr, Ti)O3 (PZT) materials. (K, Na)NbO3 (KNN)-based system has attracted extensive attention due to its’ high piezoelectric properties and Curie temperature. However, most of the researchers are concentrated on designing and controlling the orthorhombic–tetragonal transition temperature (TO–T) of KNN-based ceramics down to around room temperature, and the properties obtained are still inferior compared to PZT system.

The objective of this study is to discuss the origin of high piezoelectricity of KNN-based lead-free piezoelectric ceramics and to investigate the effect of new phase boundary on the piezoelectric properties of KNN-based ceramics. It was found that shifting the orthorhombic-rhombohedral transition temperature of KNN-based ceramics above room temperature would be accompanied with the increasing of d33 of the ceramics to ~ 480 pC/N, due to the formation of the new MPB or PPT and polar nanoregions in the KNN-based ceramics. Acknowledgment This work was supported of the National Natural Science Foundation of China (NSFC No.51332003).

Thermoelectric Properties of n-type Reduced Rare-Earth Doped SrTiO3 W. L. Schmidt,1,* A. Iyasara, 1 Z. Lu, 1 G. D. Lewin,1 D. C. Sinclair1 and I. M. Reaney1 1Department of Materials Science and Engineering, University of Sheffield, Western Bank,

Sheffield, United Kingdom *Corresponding Author: w.l.schmidt@sheffield.ac.uk

Energy waste in the form of heat reduces the efficiency of our primary energy sources.

Recovering this waste heat energy and converting it to electricity is possible using thermoelectric materials. Currently, intermetallic compounds which contain expensive, rare and toxic elements exhibit the best figure of merits (ZT) however due to their working temperatures they are limited for applications and cannot be used for the ideal waste heat scavenging applications such as in automobiles. More robust materials can be found in oxide ceramics which incorporate more earth abundant and less toxic elements. Promising candidates for n-type materials are doped SrTiO3 perovskite systems. Substituting Sr via two mechanisms Sr1-3x/2MxTiO3 or Sr1-xMxTiO3 (M = 3+ rare earth elements) has shown increased thermoelectric properties when prepared by highly reducing conditions.[1,2] In particular, the former, an A-site vacancy doping mechanism, results in materials with increased conductivity and complex defect chemistry affecting the thermal conductivity. Thus far, the highest ZT of 0.41 at 973K was found for La-doped SrTiO3 using this mechanism.[1] The working temperatures of these materials however are too high for everyday applications. The interplay of conductivity, Seebeck coefficient and thermal conductivity in RE-SrTiO3 and how synthesis conditions affect these properties will be discussed. This knowledge will lead to understanding the defect chemistry of these reduced oxides and whether the working temperature of these particular n-type materials can be reduced for implementation into oxide based thermoelectric generators.

References [1] Z. Lu, H. Zhang, W. Lei, D. C. Sinclair, I. M. Reaney, Chemistry of Materials, 28, 925 – 935 (2016) [2] A. V. Kovalevsky, A. A. Yaremchenko, S. Populoh, P. Thiel, D. P. Fagg, A. Weidenkaff, J. R. Frade, Physical Chemistry Chemical Physics, 16, 26946 – 26954 (2014)

Polarisation Dependence of Schottky Barrier Heights at Ferroelectric BaTiO3/RuO2 Interfaces: Influence of Substrate Orientation and Quality

A. Hubmann, S. Li, S. Zhukov, H. von Seggern, A. Klein* Technische Universität Darmstadt, Department of Materials and Earth Sciences

*Corresponding Author: aklein@surface.tu-darmstadt.de In situ X-ray photoelectron spectroscopy was employed to examine the change in Schottky

barrier height DFB at BaTiO3/RuO2 interfaces upon polarisation reversal for [100], [110] and [111] oriented BaTiO3 single crystals. Compared to previous measurements on BaTiO3/RuO2 interfaces [1], the crystals exhibit a significantly reduced dependence of barrier height on polarisation direction. This is connected to a much higher polarisation of the present crystals, which is comparable to the accepted bulk polarisation of BaTiO3 of 26 µC/cm2 and which exhibit the expected dependence on crystal orientation. This indicates a much higher crystal quality in the present experiments, which is also confirmed by a Kolmogorov-Avrami-Ishibashi like polarisation switching dynamics. It is observed that DFB is reduced for the [110] and [111] orientation and scales with polarisation as long as crystals from the same batch are used. The fact that a poor polarisation hysteresis behaviour relates to a high polarisation dependence of Schottky barrier height, indicates that the electrode's ability to screen ferroelectric polarisation charges depends sensitively on crystal and/or interface quality.

References [1] F. Chen, A. Klein, Phys. Rev. B 86, 094105 (2012)

Piezoresponse and Domain Evolution in Multiferroic (1-x)BiFeO3-xPbTiO3 Single Crystals

Jian Zhuang,1,2* Jinyan Zhao,1 Lun-wei Su,2 Alexei A. Bokov,2 Hua Wu,3,2 Wei Ren,1 and Zuo-Guang Ye2,1*

1Electronic Materials Research Laboratory, Key Laboratory of the Ministry of Education & International Center for Dielectric Research, Xi’an Jiaotong University, Xi’an, P. R. China 2Department of Chemistry and 4D LABS, Simon Fraser University, 8888 University Drive,

Burnaby, BC, Canada 3Department of Applied Physics, Donghua University, Ren Min Road 2999, Shanghai, P. R.

China *Corresponding Authors: jzhuang@xjtu.edu.cn ; zye@sfu.ca

As a promising single-phase multiferroic system with high ferroelectric Curie temperature (TC) and stable perovskite structure, (1-x)BiFeO3-xPbTiO3 (BF-xPT) binary solid solution has attracted increasing interests as magnetoelectrics and high-temperature piezoelectrics. In this work, the structure, phase transition behavior and polar domain configuration have been systematically studied on the single crystals of BF-xPT (x = 0.2, 0.3, 0.5) grown from high temperature solution. Structural characterization by X-ray diffraction shows a crossover from a rhombohedral R3c phase for x = 0.2, through a mixture of main tetragonal P4mm and minor R3c phases for x = 0.3, and then to a pure P4mm phase for x = 0.5. The phase transition behaviors have been studied by the temperature dependence of dielectric constant, indicating a decrease in TC from 675 oC for x = 0.2 to 525 oC for x = 0.5 with increasing PT concentration. By comparing the lattice parameters and TC of single crystals with those of polycrystalline powders [1], the actual compositions of the as-grown single crystals have been confirmed and show a higher PT concentration than the nominal compositions due to the composition segregation during the crystal growth. The domain evolution of multiferroic BF-xPT single crystals have been studied by Piezoresponse Force Microscopy (PFM) on the surface of (001) polished single crystal platelets. On the one hand, clearly banded 180o c-domains are present for the tetragonal compositions with x = 0.3 and 0.5 while no obvious 90o domains are found. The coupling of c-domains and the influence of growth steps are considered as possible reasons for the formation of the banded 180o c-domain structures. On the other hand, diverse domain patterns including the lamellar domains, island-shaped domains and wave-like domains are simultaneously revealed in the rhombohedral crystal with x = 0.2. The dominant out-of-plane piezoresponse in this single crystal suggests the existence of a skin layer with possible tetragonal symmetry [2]. In addition, the poling and switching behaviors of domains are also investigated by applying an electric filed via PFM tip, indicating typical local piezoelectricity, as shown in Fig. 1.

Figure 1. Original domain patterns, poling effects and local piezoresponse of BF-xPT single

crystal with x = 0.2.

References [1] W.-M. Zhu, H.-Y. Guo, and Z.-G. Ye , Phys. Rev. B 78, 014401 (2008). [2] X. Martí, P. Ferrer, J. Herrero-Albillos, J. Narvaez, V. Holy, N. Barrett, M. Alexe, and G.

Catalan, Phys. Rev. Lett. 106, 236101 (2011).

Domain Structures of Potassium-Substituted Sodium Niobate Films Observed By Confocal Laser Scanning Microscopy

Ichiro Fujii* and Takahiro Wada Department of Materials Chemistry, Ryukoku University, Seta, Otsu, 520-2194 Japan

*Corresponding Author: ifujii@ryukoku.ac.jp Since domain structures of ferroelectric materials affect the ferroelectric and piezoelectric

properties, observation of the domain structures is important for their applications. We previously observed a domain structure of an NaNbO3 epitaxial film by a confocal laser-scanning microscope with a polarizer, and revealed that stripe domains of antiferroelectric polarization oriented in in-plane directions were changed to different stripe domains of ferroelectric polarization oriented in out-of-plane directions by application of an electric field in an out-of-plane direction [1]. Recently, we fabricated (KxNa1-x)NbO3 epitaxial films and found that the remanent polarization was maximized at x=0.34 [2]. In this study, domain structures of the (KxNa1-x)NbO3 (x=0-0.34) films were observed by laser microscope, and the relation between the domain structures and the remanent polarization is discussed.

(KxNa1-x)NbO3 (x=0-0.34) films were deposited on SrRuO3-coated (001) SrTiO3 substrates by pulsed laser deposition [2]. Pt top circular electrodes were prepared by sputtering. The crystal structures were determined by X-ray diffraction (2θ−θ and reciprocal space mapping). The domain structures were observed by a confocal laser-scanning microscope with a reflection setting and a polarizer. The domain structures were studied after an electric field was applied.

Figure 1 shows the laser-scanning microscopy image observed with the laser polarized along the [010] direction of the SrTiO3 substrate at x=0.18 and the perovskite structure model. The stripe domains along the [110] and [1 -1 0] directions of the SrTiO3 substrate were observed. The crystal system of the film at x=0.18 was monoclinic, and the X-ray diffraction data indicated that the (KxNa1-x)NbO3 films were epitaxially grown on the SrTiO3 substrates with a cube-on-cube relation. These indicated that the domains appearing bright had polarization oriented to the [011], [0 1 -1], [0 -1 1], and [0 -1 -1] directions, and the domains appearing dark had polarization oriented to the [101], [1 0 -1], [-1 0 1], and [-1 0 -1] directions. Thus, the ferroelectric polarization in the domains was oriented in the out-of-plane direction. At x=0.30, a domain structure similar to that at x=0.18 was observed. At x=0.005 and 0.11, domain structures with the polarization oriented both in in-plane and out-of-plane directions were observed. These results were consistent with the the change in the remanent polarization in P-E loops with x.

References [1] S. Yamazoe, H. Sakurai, T. Saito, and T. Wada, Appl. Phys. Lett., 96, 092901 (2010). [2] I. Fujii, S. Tagata, T. Nakao, N. Koyama, H. Adachi, and T. Wada, Jpn. J. Appl. Phys., 54, 10NA13 (2015).

Figure 1 A domain pattern of the (K0.18Na0.82)NbO3 epitaxial film prepared on an SrRuO3/(001)SrTiO3 substrate observed by a confocal laser-scanning microscope with a laser polarized along the [010] direction of the SrTiO3 substrate. The models of perovskite cells with polarization directions for an enlarged image of the domain pattern are shown for reference. The arrows in the models indicate the polarization directions.

1

Improvement the Quality Factor of CaNb2O6 Microwave Ceramics by Substituting Ca2+ with Sr2+

Yih-Chien Chen1, and Yu-Cheng You1,* 1Department of Electrical Engineering, Lunghwa University of Science and

Technology, Gueishan District, Taoyuan City, Taiwan *Corresponding Author: mp953542@gmail.com

The benefits of using binary niobate ceramics AB2O6 are reportedly associated

with their excellent dielectric properties at microwave frequencies. A dielectric constant (εr) of 18.1, a quality factor (Q u f) of 50,000 GHz, and a temperature coefficient of resonant frequency (τf) of -54 ppm/°C were obtained when CaNb2O6 ceramics were sintered at 1400 °C for 4h [1]. Several solid solutions combining two compounds were found to have a higher value of Qu f compared with that of both end members [2-3], this phenomenon motivates this study of the effect of the substitution of Ca2+ by Sr2+ to form Ca1-xSrxNb2O6 ceramics. In this investigation, Ca1-xSrxNb2O6 ceramics were synthesized and some of the Ca2+ ions were substituted with Sr2+ ions to improve their Qu f.

The X-ray diffraction patterns of the Ca1-xSrxNb2O6 ceramics revealed CaNb2O6 is the main crystalline phase. Ca0.97Sr0.03Nb2O6 ceramics that were sintered at 1400 OC for 4 h had a maximum relative density. The microwave dielectric properties of the Ca1-xSrxNb2O6 ceramics were found to vary with the extent of Sr2+ substitution. A dielectric constant (εr) of 17.6, a quality factor (Qu f) of 80,700 GHz, and a temperature coefficient of resonant frequency (τf) of -46 ppm/°C were obtained for Ca0.97Sr0.03Nb2O6 ceramics that were sintered at 1400 °C for 4 h. The results suggest that the Qu f increased by partially substituting Ca2+ ions with Sr2+ ions. A later investigation will involve analysis of the microwave dielectric properties by densification, X-ray diffraction (XRD) patterns, and observation of their microstructures. References [1] Y.C. Chen, M.Z. Weng, K.C. Chang, Journal of Materials Science: Materials in Electronics, 25, 844-851 (2014). [2] C.L. Huang, C.Y. Tai, C.Y. Huang, Y.H. Chien, Journal of the American Ceramic Society, 93, 1999-2003 (2010) [3] T. Oishi, A. Kan, H. Ohsato, H. Ogawa, Journal of the European Ceramic Society, 26, 2075-2079 (2006)

High energy-storage performance and discharge properties of (Pb0.98La0.02)(Zr0.45Sn0.55)0.995O3 antiferroelectric thick films

X. C. Wang,1 T. Q. Yang,1,* R. Xu,2 and J. Shen1 1Key Laboratory of Advanced Civil Engineering Materials (Ministry of Education), Functional

Materials Research Laboratory, College of Materials Science and Engineering, Tongji University, 4800 Cao'an Road, Shanghai, China

2Electronic Materials Research Laboratory, Key Laboratory of the Ministry of Education, Xi’an Jiaotong University, Xi’an, Shaanxi, China

*Corresponding Author: yangtongqing@tongji.edu.cn

Dielectric materials had been studied extensively as energy pulse or power capacitors. Antiferroelectrics (AFEs) were superior to ferroelectrics and linear dielectrics because of a high energy density and a fast discharge rate. In this paper, high energy storage performance and discharge properties of (Pb0.98La0.02)(Zr0.45Sn0.55)0.995O3 AFE thick films with thickness of 85μm fabricated via a rolling process were investigated by directly measuring the hysteresis loops and pulse discharge current-time curves, and the influence of electric fields and electrode areas on the discharge properties was emphasized. As the electrode diameter of 2mm, energy storage density and the first current peak (Imax) presented a nonlinear increase with electric field increased, and Imax increased to 56A at 350kV/cm, respectively, together with the switching current density of 1830 A/cm2. Imax also exhibited nonlinear increase with the electrode diameter increasing, and increased to128A as the electrode diameter of 5mm. However the Imax only increased 2.24 times and lower than the theoretical value of 6.25, which is due to the increase of the discharge period (τ) caused by electrode areas increased, resulting in unexpectedly reduction of current density (~656A/cm2). The current density reduced but Imax increased with the electrode area increasing. These results will be contribute to research on charge-discharge properties of AFEs, and indicate that AFE thick films obtained are very promising for the pulse power application.

Figure 1. I–t curves with the electrode diameter of 2, 3, 4, and 5mm. Inset shows the current

density, measured and theoretical value ratio of maximum current and discharge period (T/4) as a function of electrode diameter.

References [1] X.F.Chen H.L. Zhang, F. Cao, et al., J. Appl. Phys. 106, 034105 (2009)

[2] M.S. Mirshekarloo, K. Yao, T. Sritharan., Appl. Phys. Lett. 97, 142902 (2010) [3] M. Ye, Q. Sun, X. Q. Chen, et al., J. Am. Ceram. Soc. 94, 3234 (2011) [4] X. Zhang, Y. Shen, Q.H. Zhang et al., Adv. Mater. 27, 819 (2015).

Application of DoE Methods to Establish a Model for the Pulsed Laser Deposition of PZT Thin-Films

A. Schatz,1,* D. Pantel,1 and T. Hanemann2,3 1Robert Bosch GmbH, Robert-Bosch-Campus 1, 71272 Renningen, Germany

2University of Freiburg, Department of Microsystems Engineering - IMTEK, Laboratory for Materials Processing, Georges-Köhler-Allee 102, 79110 Freiburg, Germany

3Karlsruhe Institute of Technology, Institute for Applied Materials (IAM), P.O. Box 3640, 76021 Karlsruhe, Germany

*Corresponding Author: Andreas.Schatz@de.bosch.com Piezoelectric thin-films made from Pb[ZrxTi1-x]O3 (PZT) have been under extensive research

during the last decades and are attractive candidates for actuator and sensor applications within micro-electro-mechanical systems (MEMS). Mass production tools for the deposition of PZT on wafer scale include chemical solution deposition and sputter deposition tools. Recently also the method of pulsed laser deposition (PLD) was made available for the deposition of PZT on large area substrates. In this work we report on the application of design of experiment (DoE) methods to establish a model for the pulsed laser deposition of PZT thin-films for MEMS applications. Implementation of the derived model allows us to predict the electrical- and electromechanical properties of as-deposited PZT thin-films.

The used PLD tool (PiezoFlare 800 by Solmates B.V.) allows an easy adjustment of the deposition pressure, wafer temperature and laser pulse energy. PZT is grown on LaNiO3 (LNO) which serves as seed layer and oxidic electrode and which also is deposited via PLD on a platinum bottom electrode in a preceding step without breaking the vacuum. As the properties of the LNO seed layer are supposed to influence the PZT film properties [1], the deposition parameters (pressure, temperature and laser energy) are varied for both, the PZT and the LNO layer, leading to a total of six continuous factors for the setup of the DoE. Several DoE responses are measured for a total set of 41 experiments and include amongst others the deposition rate R, the leakage current density Jleak and the transverse piezoelectric coefficient e31,f. The regression model for each response with respect to the factors is used to optimize the PZT thin-film. Maintaining high e31,f values at low deposition temperatures (e.g. less than 450 °C for post CMOS processes) could be one goal for an optimization iteration. An example of the model is given in Figure 1, where the temperature and oxygen pressure during PZT deposition are varied and the calculated transverse piezoelectric coefficient e31,f is shown as contour plot with color code.

Figure 1. Contour plot of the calculated e31,f with respect to the deposition pressure and

temperature while holding the other four continuous DoE factors constant.

Reference [1] H. Kim, J.-H. Kim, W.K. Choo, J. Eur. Ceram. Soc., 25, 2253-2256 (2005)

Phase transitions in the relaxor-like ferroelectric sodium bismuth titanate studiedby density functional theory calculations

K.-C. Meyer,* L. Koch and K. Albe

Materials Science, TU Darmstadt, Jovanka-Bontschits-Str. 2, Darmstadt, Germany*Corresponding Author: meyer@mm.tu-darmstadt.de

Sodium bismuth titanate (Na0.5Bi0.5TiO3, NBT) is a relaxor-like ferroelectric material atroom temperature and has interesting electrical and piezoelectric properties. [1] Below andaround room temperature the space group of NBT is close to the rhombohedral R3c withdeviations to a monoclinic symmetry. However, the space groups and phase transitions attemperatures higher than 500 K are not fully understood, especially the existence of theorthorhombic phase which has only been seen in electron diffraction, but not in XRD. In thiswork we investigate the phase transition on an atomistic level by density functional theorycalculations. Specifically, we take into account octahedral tilts, chemical order of the A-cationsand displacements of A-cations. We study the system by looking at energy barriers betweendifferent phases from nudged elastic band calculations and ab-initio molecular dynamics.Further, we provide possible explanations for the origin of polar nanoregions in NBT. [2]

References[1] K. Reichmann et al., Materials 8, 8467 - 8495 (2015)[2] K.-C. Meyer et al., J. Solid State Chem. 227, 117 - 122 (2015)

Oxygen vacancy migration in sodium bismuth titanate studied by densityfunctional theory calculations

K.-C. Meyer,* L. Koch, S. Steiner, T. Frömling and K. Albe

Materials Science, TU Darmstadt, Jovanka-Bontschits-Str. 2, Darmstadt, Germany*Corresponding Author: meyer@mm.tu-darmstadt.de

The relaxor-like ferroelectric sodium bismuth titanate (Na0.5Bi0.5TiO3, NBT) has attractedmuch interested for its interesting electromechanical properties, and recently also for its potentialuse as an ionic conductor. [1] Li et al. have shown that Mg-doped and Bi-deficient NBT exhibitsa very high ion conductivity, comparable with other known oxide ion conductors such as YSZ,GDC and LSGM. [2]

In this work we investigate oxygen vacancy migration by means of density functional theorycalculations. We study oxygen vacancy formation energies, association energies with differentdopant ions and migration barriers. We find that the chemical order of the A-cations anddifferent phases can play a strong role on the oxygen vacancy migration barriers and therefore onthe ion conductivity. Another important factor that influences the migration of vacancies are theBi lone-pair electrons.

References[1] K. Reichmann et al., Materials, 8, 8467 - 8495 (2015)[2] M. Li et al., Nat. Mater. 13, 31 - 36 (2014)

The finite Element Analysis of Nonuniform Thickness 1-3 PiezoelectricComposites for Broadband Applications

Song Xia,1,*1Electronic Materials Research Laboratory, Key Laboratory of the Ministry of Education &

International Center for Dielectric Research, Xi’an Jiaotong University, Xi’an 710049, China*Corresponding Author: sxia@mail.xjtu.edu.cn

In many transducer applications, the bandwidth has been one of the important indicators.The thickness resonant frequency determined by the thickness and velocity of the piezoelectricmaterials for the traditional transducer working with thickness resonant mode. So the resonantfrequency is very sensitive to the thickness, and the bandwidth is narrow. For piezoelectricceramic or single crystal with the nonuniform thickness, the resonant will be weakened by itsinternal lateral powerful clamping action. For 1-3 piezoelectric composites, the resonance doesnot affect strongly by each other because the piezoelectric material is distributed in the flexiblepolymer. So the nonuniform thickness 1-3 piezoelectric composites can be used for broadbandapplications. In this paper, ANSYS software is used for simulate the resonant characteristics ofnonuniform thickness 1-3 piezoelectric composites.

450 500 550 600 6500.0

0.2

0.4

0.6

0.8

1.0

Volt(V

)

Frequency(kHz)

4.0-3.66 4.0 3.66

Figure 1. The output voltage of piezoelectric composites with uniform and nonuniformthickness

The simulation showed that the1-3 piezoelectric composites with nonuniform thickness canimprove bandwidth effectively.

References[1] John A. Hossack, Gordon Hayward, IEEE Transactions on Ultrasonics, Ferroelectrics andFrequency Control, 38, 618-629 (1991)[2] L.J.Bown, T.R.Gururaja, Journal of Applied Physics, 51, 5661-5666(1980)

Status of Ferroelectric HfO2 based 1T FeFET Memories (invited) T. Mikolajick,1,2*, U. Schroeder,1 S. Slesazeck1, S. Müller1, T. Schenk1, and J. Müller3

1NaMLab gGmbH, Noethnitzer Str. 64, Dresden D-01187, Germany 2IHM TU Dresden , Noethnitzer Str. 64, Dresden D-01187, Germany

3Fraunhofer IPMS-CNT, Koenigsbruecker Strasse 180, D-01099 Dresden, Germany *Corresponding Author: thomas.mikolajick@namlab.com

Based on the physical mechanism, ferroelectrics are ideally suited as the active material in

nonvolatile memories, since during switching only the minimum current required to move the charges of the dipole is flowing and hence ferroelectricity promises both low power writing and nonvolatility [1]. Therefore, already in the 1950 the possibility to use ferroelectrics in nonvolatile memories has been exploited [2]. When the effect was combined with the then established semiconductor technology in the late 1980s, first products were realized [3]. However, traditionally the ferroelectric effect is observed in perovskites or layered perovskites like lead zirconium titanate (PZT) or strontium bismuth tantalate (SBT). These materials have a complex structure and are extremely difficult to integrate into a semiconductor process [4]. As a result, ferroelectric memories are scaling much slower than their floating gate or charge trapping based counter parts and are therefore limited to niche applications. In 2011 it was first reported that ferroelectricity can be observed in hafnium oxide based materials which are already established as gate dielectrics in modern CMOS transistors [5]. This discovery solves the CMOS compatibility issue. Due to the much lower permittivity and the higher coercive field in this materials, they also enable 1T ferroelectric field effect transistors [6] that were extremely difficult to realize based on PZT or SBT materials [7]. In the last five years significant research efforts were undertaken to clarify the physical origin of the ferroelectricity in hafnium oxide and on the other side exploit its practical application in 1T ferroelectric FET based memories. Table 1 puts this new approach in the context of the earlier developments of ferroelectric memories. This paper will first summarize the fingerprint of the ferroelectric effect in hafnium oxide. The second part will give insight into the current understanding of its physical basis. Finally the status of its implementation in 1T ferroelectric FET memories will be discussed.

Table 1. Evolution of ferroelectric memories. Based on the available material and technology boundary conditions, three generations of ferroelectric memories can be identified.

References [1] J. F. Scott, Ferroelectric Memories, Springer-Verlag, Berlin (2000) [2] D.A. Buck, master thesis, MIT Digital Computer Laboratory (1952) [3] D. Bondurant, Ferroelectrics 112, 273-282 (1990) [4] C.-U. Pinnow, T. Mikolajick, J. Electrochem. Soc. 151, K13-K19 (2004) [5] T. S. Böscke et al., Appl. Phys. Lett., 99, 112904 (2011) [6] J. Müller qt al., IEEE Electron Device Lett. 33, 185-187 (2012) [7] T.P. Ma and J.-P. Han, IEEE Electron Device Lett. 23, 386-388 (2002)

Oxide ion conductivity in Mg-doped Na0.5Bi0.5TiO3-based ceramics Jinqiang Huang1, Fangyuan Zhu2, Jianzhong Xiao1, Haibo Zhang1,*

1College of Materials Science and Engineering, State Key Laboratory of Material Processing and Die &Mould Technology, Huazhong University of Science and

Technology, Wuhan 430074, PR China 2Shanghai Synchrotron Radiation Facility, Shanghai Institute of Applied Physics,

CAS, Shanghai 201204, PR China *Corresponding Author: hbzhang@mail.hust.edu.cn

Na0.5Bi0.5TiO3 (NBT) based oxide-ion conductor ceramics have great potential

applications in intermediate-temperature solid-oxide fuel cells (SOFCs) and oxygen sensors. To design a new material with high oxide-ion conductivity and negligible electronic conductivity at a reasonable low temperature, Na0.5Bi0.49Ti1-xMgxO3-δ

ceramics with x=0-0.05 and 0.08 were prepared by conventional solid-state reaction. The XRD measurement and SEM analysis revealed the formation of pure perovskite structures without secondary phase. MgO doping greatly decreased the sintering temperature and inhibited grain growth. Ac impedance spectroscopy measurement was adopted to measure the total conductivity, which was found to increase with the increasing MgO content from 0 to 3 mol% and subsequently to decrease. The creation of oxygen vacancy contributes to conductivity increase when MgO content varys from 0 to 3 mol%. The formation of defect association might be responsible for the decrease of conductivity in samples with higher content. High oxygen ionic conductivity σt= 0.00629 S/cm was achieved for sample doped with 3 mol% MgO at 600 °C in air atmosphere. Compared with other conventional materials, the Na0.5Bi0.49Ti1-xMgxO3-δ shows a great potential in application of intermedium temperature SOFC.

Figure 1. Arrhenius plots of the total conductivity for Na0.5Bi0.49Ti1-xMgxO3-δ (x=0, 0.01, 0.02, 0.03, 0.05 and 0.08).

Figure 2.The total conductivity for Na0.5Bi0.49Ti1-xMgxO3-δ (x=0, 0.01, 0.02, 0.03, 0.05 and 0.08) at 400 °C, 500 °C and 600 °C.

Effective dielectric function of BaTiO3-NiO composites D. Nuzhnyy,1 J. Petzelt,1* M. Savinov,1 V. Bovtun,1 M. Kempa,1 P. Bednyakov,1

L. Fernández-Garciá,2 T. Rodriguez-Suarez,2 and J. L. Menendéz2

1Institute of Physics, Czech Academy of Sciences,

Na Slovance 2, Praha 8, 18221 Czech Republic 2Centro de Investigación en Nanomateriales y Nanotecnología (CINN),

Consejo Superior de Investigaciones Científicas, Universidad de Oviedo, Avd. de La Vega 4-6, El Entrego, Spain, 33940

*Corresponding Author: petzelt@fzu.cz

Topology of the constituents in composites plays an important role in the effective dielectric

response of high-permittivity and absorbing materials with a strong dielectric contrast between the constituents. Here we studied the broadband dielectric spectra of two types of topology in composites of the same concentration: BaTiO3 (BTO) with 30 vol.% of NiO prepared by the spark plasma sintering from different powders. The core-shell BTO@NiO composites were sintered from BTO powder particles (~0.7 µm) covered by nanometric NiO shells and the standard composites were sintered from a mixture of the same type of BTO powder and larger NiO powder particles (several µm with a broad size distribution). Structural characterization confirmed the same structure as in the bulk: ferroelectric perovskite BTO and NiO of rock-salt structure.

By using several techniques: low-frequency (1 Hz - 1 MHz) and high-frequency (1 MHz - 1 GHz) dielectric spectroscopy, time-domain terahertz transmission (0.2 - 2 THz) and infrared reflectivity (1 - 30 THz) in a broad temperature range (10 - 700 K), we covered ~13 orders of magnitude in frequency, where we evaluated and fitted the complex dielectric function using phenomenological models, with strongly differing results for both the composites. The ferroelectric phase transition near 400 K was apparent in both composites through a maximum in the temperature dependent low-frequency permittivity and a minimum in the overlapped soft mode-central mode frequency, more pronounced in the standard composite.

The effective dielectric spectra were also calculated using various models based on the effective model approximation (EMA) with different composite topologies, by using the dielectric functions of the neat components (BTO dense coarse-grain ceramics [1] and NiO single crystals [2]). Since the BTO spectra are rather complex (particularly in the polar phonon range), no perfect agreement between the measured and calculated spectra was obtained. But the best results were achieved using the Lichtenecker model, which corresponds to a very complex topology of the constituents with one free fitting parameter characterizing the degree of constituent percolation [3]. The coated-spheres model (Hashin-Shtrikman) [3], expected to work better for an ideal BTO@NiO composite, was not so good, indicating partial percolation of the BTO (not ideally covering the cores with the NiO shells) or some interdiffusion between the cores and shells. References [1] J. Petzelt et al., Ferroelectrics 469, 14 (2014). [2] Ch. Kant, F. Mayr, T. Rudolf, M. Schmidt, F. Schrettle, J. Deisenhofer, and A. Loidl, Eur.

Phys. J. Special Topics 180, 43 (2010). [3] J. Petzelt et al., Phys. Stat. Sol. A 210, 2259 (2013).

Ferroelectricity and Non-ferroelectricity in Lead-free La and Y – Doped HfO2 Bulk Ceramics and Thin Films

B. S. Johnson,1,* C. C. Chung,1 S. Jones,1 M. Kasper,1 and J. L. Jones1 1Materials Science and Engineering, North Carolina State University 911 Partners Way, Raleigh, NC,

United States *Corresponding Author: bsjohns5@ncsu.edu

There have been intensive studies of ferroelectric materials because of their ability to be used for

various applications including non-volatile memories, energy harvesting, and sensors. Recently, ferroelectricity was discovered in HfO2 thin films which enabled HfO2 to be considered for lead free ferroelectric capacitors or transistors for non-volatile memories. The origin of ferroelectricity in HfO2 has been attributed to chemical doping and the stress induced by the substrate and capping layers. Si-doped HfO2 films were the first to be found exhibiting ferroelectric properties. [1-2] Since the discovery of Si-doped HfO2 films, other dopants including Y and La have also been found to induce ferroelectricity in HfO2 films by Muller et al in 2011 and 2013.[3-4] Although the ferroelectric properties of doped HfO2 films have been rigorously investigated, fundamentals of the relationship between the observed ferroelectric properties and underlying structure are still not fully understood. Previous studies of Si-doped HfO2 powders have shown that there was an increase in the unit cell volume and the solubility limit of Si into HfO2 is less than 9%. It was also determined that heat treatments affected the phase and structure of Si-doped HfO2. This led to an understanding of the structural origins of ferroelectricity in Si-doped HfO2.[5-7]

This research investigates the structure changes in La and Y doped HfO2 bulk powders. HfO2 powders were doped with La2O3 (1%, 3%, 5%, and 7%) or Y2O3 (1%, 5%, 7%, 9%, 15%, 19%, and 50%) then heat treated to 1100°C - 1500°C. X-ray diffraction patterns were measured for each of the doped HfO2 powders to determine the structures changes that occurred due to doping and heat treatment. These studies, performed on doped HfO2 powders, provide complementary structural information to the thin films and computational modeling. This data was analyzed using Rietveld refinement to quantify changes in HfO2 lattice parameters, phase fractions, atomic occupancies, solubility due to doping and heat treatments. La – doped HfO2 XRD results show the formation of the Hf2La2O7 phase above ~3% and increases with dopant concentration. It is observed in the Y-doped HfO2 XRD results, that with increasing Y concentration and heat treatment temperature, the cubic phase of HfO2 begins to form and increases in phase fraction (figure 1). Although ferroelectricity has not been observed in the bulk ceramic form of HfO2, this systematic investigation leads to insight into the changes in the crystallographic structure with doping. References [1] M. Park et al. Adv. Mater. 27, 1811-1831 (2015). [2] U. Schroeder et al. Jpn. J. Appl. Phys. 53, 08LE02 (2014) [3] J. Müller et al. J. Appl. Phys. 110, 114113 (2011). [4] J. Müller et al. IEEE International Electron Devices Meeting (2013) [5] L. Zhao et al. Appl. Phy. 115, 034104 (2014). [6] L. Zhao et al. J. Allo. & Comp. 646 (2015). [7] D. Hou et al. J. Appl. Phys. 117, 244103 (2015).

C

M

Figure 1: XRD patterns of 9% and 19% Y doped HfO2 heated to 1100°C and 1400°C. (C=Cubic HfO2 phase, M=monoclinic HfO2 phase.

In-operando detection of interface details in filament-type resistive random access memory (RRAM) using hard X-ray photoelectron spectroscopy (HAXPES)

G. Niu1,2*, P. Calka2, S. U. Sharath3, S. Vogel3, A. Gloskovskii4, K. Fröhlich5, J. Soltys5, F. Bärwolf2, W. Seifert2, C. Wenger2, L. Alff3 and T. Schroeder2,6

1Electronic Materials Research Laboratory, Key Laboratory of the Ministry of Education & International Center for Dielectric Research, Xi'an Jiaotong University, Xi'an 710049, China.

2 IHP, Im Technologiepark 25,15236 Frankfurt (Oder), Germany 3Institute of Materials Science, Technische Universität Darmstadt,64287 Darmstadt, Germany

4Deutsches Elektronen-Synchrotron DESY, Notkestrasse 85, 22607 Hamburg, Germany 5Institute of Electrical Engineering, Slovak Academy of Sciences, Dúbravská cesta 9, 841 04 Bratislava,

Slovakia Bratislava, Slovakia 6Brandenburgische Technische Universität, Konrad-Zuse-Strasse 1,03046 Cottbus, Germany

*Corresponding Author: gangniu@mail.xjtu.edu.cn

HfO2 based resistive random access memories (RRAM), thanks to their virtues such as the non-volatile (106 s), fast (< 10 ns) and low-power (1 pJ/bit) operation and the compatibility with the current semiconductor fabrication process, represent one of the most promising candidates for future embedded memories. HfO2 RRAM devices generally consist of a metal-insulator-metal (MIM) structure. Its resistive switching (RS) mechanism is related to the forming/breaking a few nanometer wide conductive filament (CF) consisting of oxygen vacancies (VO) in the HfO2 layer. The material nature in the CF is of great significance for understanding the RS process and improving the device performance. However, due to its nm scale feature, it is very challenging to probe the material modification inside the filament. On the other hand, even for such filament type devices, it is found that the MIM interface details are important because electrodes such as Ti or TiN serve as oxygen reservoirs, which strongly influence the VO formation in HfO2 [1]. X-ray photoelectron spectroscopy (XPS) has been proven as a powerful non-destructive tool to study the physico-chemical properties of thin films, nonetheless conventional XPS (hν<2 keV) is limited to the probing depth of 1-2 nm. Synchrotron radiation based hard X-ray photoelectron spectroscopy (HAXPES) using high excitation energies thus having the larger inelastic mean free path (IMFP) of the excited electrons and the larger probing depth [2], allows bulk sensitive physico-chemical analysis of interface details of MIM structures.

In this study we demonstrate an in-operando investigation of interface details of a Pt/HfO2/TiN stack on Si (001) during its RS by using HAXPES (hν=8 keV) at P09 beam line at DESY in Hamburg, Germany. The device shown in Figure 1(a) shows a well-defined RS behavior. Both Pt/HfO2 and HfO2/TiN interfaces were analyzed in-operando for each RS state including pristine, formed, set and reset. Figure 1 (b) shows the Hf 4f and Ti 2p spectra for pristine and formed states of the same device. We found that the RS process is along with an oxygen exchange between the HfO2 layer and the TiN bottom electrode. This demonstrates the importance of the MIM interface for RS and also indicates that HAXPES can be used as a powerful diagnostic tool to monitor the RS process in RRAM devices.

Figure 1. (a) Pt/HfO2/TiN/Si stack details and RS properties; (b) In-operando HAXPES of

Hf 4f and Ti 2p spectra for pristine and formed states of the same device, showing that oxygen ions move from HfO2 to TiN. Peaks with darker color show components with more oxygen.

References [1] J.-W. Yoon et al., Nanoscale vol 6, 6668 (2014) [2] M. Sowinska et al., J. Appl. Phys. vol 115, 204509 (2014)

Potassium-Sodium Niobate based Lead-free Relaxor Ferroelectric Ceramics for Energy Storage Applications

Shaobo Qu,1,* Hongliang Du,1 Hua Ma,1 Xiaoyong Wei,2 and Zhuo Xu2 1State Key Laboratory of Solidification Processing, Northwestern Polytechnical University,

Xi’an, 710072, China 2Electronic Materials Research Laboratory, Key Laboratory of Educational Ministry, Xi’an

Jiaotong University, Xi’an 710049, China

*Corresponding Author: qushaobo@126.com

(K0.5Na0.5)NbO3 (KNN)-based lead-free relaxor ferroelectric ceramics were synthesized by

solid-state reaction technique. The dielectric and ferroelectric properties of KNN-based ceramics were measured. Energy-storage properties of KNN-based lead-free ceramics were first investigated. A maximum recoverable energy-storage density of 2.3 J/cm3 and efficiency of 72 % were achieved in the KNN-based ceramics at the breakdown dielectric strength of 300 kV/cm. These results indicate that the KNN-based ceramic could be a potential candidate for applications in high energy-storage density capacitors. On the other hand, This study also expands the applications of KNN-based ceramics into new areas beyond piezoelectric ceramics.

References [1] B. Qu, H. Du and Z. Yang, J. Mater. Chem. C, 4, 1795-1803, (2016). [2] J. Wu, D. Xiao and J. Zhu, Chem. Rev., 115, 2559−2595, (2015) [3]J. Rodel, K. G. Webbera, R. Dittmera, W. Jo, M. Kimurac, and D. Damjanovic, J. Eur. Ceram. Soc., 35,1659–1681, (2015)

Self-Ordering and Self-Assembly of Domains and Domain Walls in Ferroelectrics M. P. Campbell1, J. McConville1, A. Schilling1, R. G. P. McQuaid1, A. Kumar1, A. M.

Glazer2,3, P. A. Thomas2 and J. M. Gregg,1,* 1School of Mathematics and Physics, Queen’s University Belfast, University Road, Balfast, N.

Ireland, U. K. 2Department of Physics, University of Warwick, Gibbet Hill Road, Coventry, U. K.

3Clarendon Laboratory, Parks Road, Oxford, U. K. *Corresponding Author: m.gregg@qub.ac.uk

This purpose of this talk will be to present and discuss two aspects of self-ordering / self-

assembly in ferroelectrics, where scanning probe microscopy (SPM) has helped generate critical insight: the first, concerns the thermodynamic origins of the stunningly regular square-net birefringence patterns (or “Forsbergh” patterns) that have been seen to form in flux-grown BaTiO3 single crystals (see figure 1 below). We have reexamined these crystals, but see no direct evidence for the intricate tessellating arrangements of domain packets put forward by Forsbergh in his original work [1]. We propose a much less exotic explanation, where complex birefringence arises from orthogonally oriented ferroelastic stripe domains simply overlaying one another. We see that Forsbergh birefringence patterns only occur if the periodicity of the stripe domains is above a critical value. Using well-established semiempirical models and direct measurement, we show that domain coarsening is fully expected in a narrow window just below the Curie Temperature (where Forsbergh patterns appear).

The second topic for discussion concerns the spontaneous self-assembly of p-n junctions within domain walls in hexagonal rare-earth manganites. Enhanced electrical conductivity (and perhaps even superconductivity) at “charged” domain walls in ferroelectrics has now been seen in a number of materials systems by a variety of groups worldwide [2]. It is thought that charged walls attract free charge carriers, of either n or p-type depending on the nature of the polar discontinuity across the wall. When two different “polarities” of domain walls meet (as occurs at specific junctions in some manganite systems) 1D line p-n junctions can spontaneously form. We will discuss these junctions, their characterization and their properties.

Figure 1. Some flux-grown BaTiO3 single crystals appear to exhibit spontaneous ordering of domains just below the Curie Temperature through stunningly regular square-net birefringence

patterns (known as “Forsbergh patterns” after their original discoverer [1]).

References [1] P. W. Forsbergh, Jr., Phys. Rev., 76, 1187 (1949) [2] J. Seidel et al., Nat. Mater., 8, 229 (2009); J. Guyonnet et al., Adv. Mater., 23, 5377 (2011); D. Meier et al., Nat. Mater., 11, 284 (2012); M. Schröder et al., Adv. Funct. Mater., 22, 3936 (2012). T. Sluka et al., Nat. Commun., 4, 1808 (2013).

Make stress is your ally Brahim Dkhil

Laboratoire Structures, Propriétés et Modélisation des Solides, CentraleSupélec, CNRS-UMR8580, Université Paris-Saclay, 92290 Châtenay-Malabry, France

*brahim.dkhil@centralesupelec.fr Ferroelectric oxides are known to be very sensitive to any external "mechanical" stress.

Such stress can be applied through various paths. Usually, the approaches to induce 3D, 2D or 1D stress use diamond anvil cell technique for hydrostatic pressure, thin film clamping for biaxial epitaxy stress or tensile/compression machine for uniaxial stresses, respectively. In this talk, I will present some examples showing how good stress can be very useful for functional oxides through the tuning or improvement of their physical properties and how such stress can be smartly generated. Among the illustrations and depending on time, I will show how 1) stress (uniaxial to isotropic) can be favorably used to improve caloric responses in BaTiO3 through mechanocaloric effect being as big as the electrocaloric counterpart [1-3]; 2) stress can be used in artificial multiferroics like FeRh/BaTiO3, to generate unprecedented magnetoelectric coupling [4,5] or impact on the magnetocaloric losses [6]; 3) an unusual 3D stretching (negative pressure) can be realized in PbTiO3 nanowires via an original core-shell structure and induce enhanced ferroelectric properties [7]; 4) in case of the model multiferroic BiFeO3, in which the stress is beneficial to tune the structure as well as the functional ferroelectric and magnetic properties [8-10], one can use light excitation [11] and especially ultra-fast laser pulses to induce strong and useful coherent acoustic waves [12-14].

References [1] Y. Liu et al., Phys. Rev. B 90, 104107 (2014) [2] Y. Liu et al., Appl. Phys. Lett. 104, 162904 (2014) [3] Y. Liu et al., Adv. Mater. 26, 6132 (2014) [4] R. O. Cherifi et al., Nat. Mater. 13, 345 (2014) [5] L.C. Phillips et al., Sci. Rep. 5, 10026 (2015) [6] Y. Liu et al., Nat. Comm., in press (2016) [7] J. Wang et al., Nat. Mater. 14, 985 (2015) [8] Y. Yang et al., Compt. Rend. Phys. 16, 193 (2015) [9] C. Daumont et al., J. Phys.: Condens. Matter 24, 162202 (2012) [10] D. Sando et al., Nat. Mater. 12, 641 (2013) [11] C. Paillard et al., Adv. Mater. in press (2016) [12] M. Lejman et al., Nat. Comm. 5, 4301 (2014) [13] C. Paillard et al., Phys. Rev. lett., under review (2016) [14] M. Lejman et al., Nat. Comm., under review (2016)

Improved Electrical Properties and Dual-mode Photoluminescence in

(1-x)(Na0.475K0.475Li0.05)NbO3-x(Er0.5Na0.5)TiO3 Lead-free

Multifunctiona Ceramics

Xiaona Chai, Jun Li, Xusheng Wang*,Yanxia Li and Xi Yao

Key Laboratory of Advanced Civil Engineering Materials of the Ministry of

Education, Functional Materials Research Laboratory, School of Materials Science

and Engineering, Tongji University, 4800 Cao’an Road, Shanghai 201804, China

*Corresponding . E-mail: xs-wang@tongji.edu.cn

(1-x)(Na0.475K0.475Li0.05)NbO3-x(Er0.5Na0.5)TiO3 (0≤x≤0.025) lead-free

multifunctional ceramics were prepared by a conventional solid-state reaction method.

Their phase, photoluminescence, dielectric, ferroelectric and piezoelectric properties

were investigated systematically by the X-ray Diffraction (XRD), scanning electron m

icroscopy (SEM), spectrophotometer and electrical property measurements. The relati

onship of composition, microstructure and electrical properties and the mechanisms of

up-conversion and down-conversion emissions were analyzed detailed. The results sh

ow that the ceramics exhibit the optimum piezoelectric and ferroelectric properties wh

en there compositions lie at the nearby of the morphotropic phase boundary (MPB).

Moreover, these ceramics can emit strong 550 nm green light when they were excited

by a near-infrared (980 nm) light and a 486 nm blue light, respectively. Together with

the excellent ferroelectric properties and good dielectric properties, these ceramics sh

ould be one of the promising candidates for multifunctional optoelectronic application

s.

Lead-free piezoelectric epitaxial KNN-BZ-BNT thin films on STO single

crystalline substrates

Wen Chen, Lingyan Wang*, Wei Ren, Nan Zhang, Gang Niu and Ming Liu

Electronic Material Research Laboratory, Key Laboratory of the Ministry of Education &

International Center for Dielectric Research, Xi'an Jiaotong University, Xi'an 710049, China

*Corresponding Author: l.y.wang@mail.xjtu.edu.cn

Since the 0.915K0.5Na0.5NbO3-0.075BaZrO3-0.01Bi0.5Na0.5TiO3 (KNN-BZ-BNT) bulk ceramics

show excellent piezoelectric properties with a good thermal stability, as the formation of vertical

morphotropic phase boundary [1], the KNN-BZ-BNT thin films were studied. To investigate the

crystal phase and further optimize the performances of films, the epitaxial KNN-BZ-BNT films

were deposited on the single crystals SrTiO3 substrates with different orientations by a chemical

solution deposition method. All the films exhibited a perovskite single-phase structure with

enhanced peak intensity in accordance with the orientations of single crystalline SrTiO3

substrates. RSM and TEM results show a rhombohedral symmetry with the lattice constant of

a=b=c=3.99 Å for all films. All the films show improved electrical properties, with a higher

dielectric constant of about 720 and lower dielectric loss of about 0.04-0.05, as well as the strong

piezoelectric response. The (100)-oriented KNN-BZ-BNT film shows the strongest piezoelectric

response. The domain structures of all films were investigated, which the out-of-plane domains

are oriented in same polarization, while the in-plane domains are randomly polarized.

References [1] T. Karaki, T. Katayama, K. Yoshida, S. Maruyama, and M. Adachi, Jpn. J. Appl. Phys. 52, 09KD11 (2013).

Ferroelectric domains and phase transition of sol-gel processed epitaxial Sm-doped BiFeO3/Nb:SrTiO3 (100) thin films

Wei Sun, Zhen Zhou and Jing-Feng Li* State Key Laboratory of New Ceramics and Fine Processing, School of Materials Science and

Engineering, Tsinghua University, Beijing, China, 100084 *Corresponding Author: jingfeng@mail.tsinghua.edu.cn

BiFeO3 is a promising ferroelectric and piezoelectric material, whose phase transition has

attracted attention with a recent finding on a rhombohedral-orthorhombic morphotropic phase boundary (MPB) in Sm-doped BiFeO3. Despite the importance of domains in piezoelectric materials, the investigations on domain characteristics in Sm:BiFeO3 thin films are very limited. In this work, 12% Sm doped BiFeO3 epitaxial thin films were fabricated on Nb:SrTiO3 (100) single crystal substrates via sol-gel method. The epitaxy was verified by RSM and TEM. SAED indicated the coexistence of R3c and Pbam phases in the film. PFM was employed to characterize the domains and piezoelectric properties from room temperature to 200 oC. Domain configurations were obtained along both in-plane (IP) and out-of-plane (OP) directions using dual AC resonant tracking (DART) mode. It revealed that domains became active from 110 oC to 170 oC and domain configurations changed obviously. At the same time, some regions lost piezoresponse, which might correspond to the emergence of antiferroelectric Pbam or non-ferroelectric Pnma phase. At 200 oC, both IP and OP domains disappeared, indicating the completion of phase transition. The in-situ domain analysis suggested that the phase transition took place in a wide temperature range from 110 oC to 170 oC, which was accompanied with the domain wall motion. SS-PFM was further carried on to investigate the piezoelectric response of Sm:BiFeO3 thin films during the phase transition. Anomalous responses were found in both ON and OFF states at 170 oC. Besides, the film exhibits typical antiferroelctric behavior at 200 oC, implying that transition to the Pbam phase.

Low Loss Magneto-dielectric Composite Ceramics Ba3Co2Fe24O41/SrTiO3 for High Frequency Applications

P. P. Chang1, L. He1, and H. Wang1 1 School of Electronic and Information Engineering and State Key Laboratory for Mechanical

Behavior of Materials, Xi’an Jiaotong University, Xi’an, 710049, China *Corresponding Author: hwang@mail.xjtu.edu.cn

With the rapid development of information and electronic technology, the increasing

requirements on electronic devices make components developing along the line of multifunction and miniaturization. Thus, the multifunctional materials, especially the magneto-dielectric composites, exhibit a wide variety of practical applications and attract tremendous attentions. It is desirable to develop the magneto-dielectric composites with relative high permittivity and permeability, low dielectric and magnetic loss, and good frequency stability for high frequency applications. In this work, magneto-dielectric composite ceramics Ba3Co2Fe24O41/SrTiO3 (Co2Z/STO) loading with high volume fraction of hexaferrite Co2Z (fCo2Z =60%-95%) are successfully prepared by a hybrid process. The microstructures with homogeneously dispersed constituent grains are observed in these composites.

Figure 1. The microstructures and magneto-dielectric properties of the Co2Z/STO ceramics

These magneto-dielectric Co2Z/STO composites are revealed to be a combination of low

loss and wide frequency stability of both permeability and relative permittivity from 10 MHz to 1 GHz. For the composite loading with 60% Co2Z, the dielectric loss tangent keeps below 0.009 within the frequency range from 10 MHz to 1 GHz. Also, it possesses a magnetic loss tangent of 0.006 and 0.144 at 50 MHz and 1 GHz, respectively, which are much lower than 0.056 and 1.242 of the single Co2Z phase at the same frequency. These excellent properties indicate that the low loss Co2Z/STO composite ceramic is a new kind of multifunctional magneto-dielectric material with potential for high frequency electromagnetic device applications.

References [1] P.P. Chang, L. He, H. Wang, J. Am. Ceram. Soc, 98, 1137 (2015)

Templated Grain Growth and Piezoelectric Properties of <001>-

Textured PIN-PMN-PT Ceramics Dan-dan Wei, Qi-bin Yuan, Gao-qun Zhang, Hong Wang*

School of Electronic and Information Engineering and State Key Laboratory for Mechanical

Behavior of Materials, Xi’an Jiaotong University, Xi’an, 710049, China *Corresponding Author: hwang@mail.xjtu.edu.cn

Recently, relaxor-PT based ternary single crystals in the Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 (PIN-PMN-PT) system have been extensively studied because of the high Tc and TR-T. However, there are several drawbacks associated with the single crystals, such as high production cost, long growth time and poor compositional uniformity, which limit their applications. Thus, it is very essential to enhance the performance of the PIN-PMN-PT ceramics. Microstructure texturing is an effective method. In this study, the <001> textured PIN-PMN-PT ceramics were successfully prepared by the templated grain growth (TGG) method.

Figure 1. The XRD , SEM and strain of the random and textured ceramics

The highest Lotgering factor of 95% has been achieved for the textured ceramics. The Curie temperature and dielectric constant of the textured 36PIN-30PMN-34PT ceramics were 225oC and 2850, respectively. The piezoelectric constant d33 of the textured samples was 780 pC/N and almost 2 times higher than that of random 36PIN-30PMN-34PT samples. Unipolar strain-field measurements for the textured ceramics exhibited 0.34% strain at 4 kV/mm.

References [1] Dan-dan Wei, Qi-bin Yuan, Gao-qun Zhang, Hong Wang, J. Mater. Res., 30(14), 2144-50(2015)

Influence of poling on the domain structure in relaxor-ferroelectric (1-x)Pb(Mg1/3Nb2/3)O3–xPbTiO3 ceramics

H. Uršič,* M. Vrabelj, S. Drnovšek, B. Kmet and B. Malič

Electronic Ceramics Department, Jožef Stefan Institute, Jamova cesta 39, Ljubljana, Slovenia *Corresponding Author: hana.ursic@ijs.si

The relaxor-ferroelectric (1-x)Pb(Mg1/3Nb2/3)O3–xPbTiO3 (PMN–100xPT) ceramics with compositions x = 0.1 – 0.4 exhibit high dielectric permittivity, polarization, electromechanical (piezoelectric or electrostrictive) and electrocaloric effects. They can be used for different applications, such as piezoelectric transducers, sensors, actuators, and cooling devices of a new generation. The domains and their configuration play a major role in the piezoelectric response and ferroelectric switching. They can be efficiently determined by the piezoresponse force microscopy (PFM). Until now the domain structure in PMN–100xPT has been studied by PFM mainly in single crystals and only a few studies were performed on ceramics [1].

In this work, the complex domain structure in polycrystalline PMN–100xPT (x = 0.1 – 0.4) is reported. The ceramics was prepared by sintering of the mechanochemically-synthesized powder compacts. The average grain size in ceramics was between 2 – 3 μm. The domain size increases with increasing PT content (fig. 1). A few hundred nanometres large irregularly shaped domains were observed in the ceramics with the lowest PT content, and a micrometre sized lamellar and irregular domains were observed in the ceramics with the highest PT content.

Considering that one of the main potential applications of these materials is in piezoelectric transducers, actuators and sensors, the domain structure of the poled ceramics was also investigated. Ex-situ poling of the ceramics was performed such that no additional mechanical or thermal treatment was applied between the PFM measurements of non-poled and poled ceramics. After the DC poling by 40 kV/cm at room temperature, the number of domains in the ceramics was suppressed; nevertheless the domains with a similar morphology as the one before poling were clearly observed.

Figure 1. PFM out-of-plane amplitude images showing the domain structure in non-poled ceramics. The authors acknowledge the Slovenian Research Agency (P2-0105, L2-6768 and J2-7526). References [1] V. V. Shvartsman, A. L. Kholkin, J. Appl. Phys. 108, 042007 (2010).

(c) (b) (a)

(a)

Domain engineering using a Si-electrode stamp H. Kianirad,1,* A. Zukauskas,1 C. Canalias,1 and F. Laurell1

1 Applied Physics Department, Royal Institute of Technology, Roslagstullsbacken 21, SE-106 91 Stockholm, Sweden

*Corresponding Author: kianirad@kth.se Tailored 180º domain structures in ferroelectric bulk crystals like LiNbO3 and KTiOPO4

(KTP), are frequently used for applications in nonlinear optics and electro-optics. The individual domain size is on the order of tens of µm down to sub-µm, and the patterned area from several mm2 to full 3"-wafers are used. The required domain structure is normally obtained by electric field poling using lithographically patterned electrodes deposited on the z-face of the crystal. This is a fairly straightforward technology today when the domain size is 10 µm or larger, but ordinary patterning techniques do not work when the domain size goes down to below 1 µm.

In this work we present a technique for fabrication of 1D and 2D small size domains structures by using a Si- template electrode for electric field poling. The Si-electrode can be fabricated by e-beam lithography and dry etching to get high resolution features far smaller than the 1 µm limit set by conventional lithography.

Among the ferroelectric oxides used for periodic poling, the crystals from the KTP family are considered to be the most suitable for fabrication of fine-pitch, one-dimensional domain gratings because of the large anisotropy in ferroelectric domain-propagation velocity along the different crystalographic axes [1]. Bulk Rb-doped KTP (RKTP) is a particularly attractive KTP isomorph with much lower ionic conductivity relative to KTP which ease the poling [2]. We have used 1 mm thick z-cut RKTP and demonstrated several 1D and 2D domain lattices. An example of a 2D fabrication is shown in Fig.1. The Si-stamp electrode consist of thin pillars with a flat top contact area as seen in Fig. 1.a. A schematic of the poling set up is seen in Fig.1.b, and the resulting regular and homogeneous domain pattern with a 5×5 µm2 period is revealed by chemical etching as seen in Fig. 1.c. The homogeneity and the high quality of the domains was verified by optical frequency doubling using a Ti:sapphire laser and close to ideal performance was obtained. Furthermore, it can be seen in Fig. 1 that the individual domains are somewhat larger than the electrode contact area, and that they also become elongated. This is due to slight overpoling and the fact that domain growth is preferred in the y-direction for RKTP [1].

Figure 1. (a) Si-stamp electrode fabricated by dry etching; (b) Poling set-up; (c) 5×5 µm2 domain structure.

This novel technique has several advantages over conventional poling. First, the silicon

electrode is reusable and there is no need for patterning each sample individually. Second, the crystalline structure of silicon provides high accuracy and reproducibility in the electrode fabrication. Finally, Si-pillar array electrodes can be easily designed for any desirable period or electrode geometry. We believe that stamp electrode poling can be a more convenient, flexible and suitable method for making small feature and large area domain patterns, necessary for the next generation engineered ferroelectrics at a reduced fabrication costs.

References [1] C. Canalias, J. Hirohashi, V. Pasiskevicius, and F. Laurell, J. Appl. Phys. 97, 124105, (2005). [2] Q. Jiang, P. A. Thomas, K. B. Hutton, and R. C. C. Ward, J. Appl. Phys. 92, 2717, (2002).

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Fabrication of 0.9Pb((Mg, Zn)1/3Nb2/3)O3 - 0.1PbTiO3 Transparent Ceramics Saki Nakashima, Ichiro Fujii, and Takahiro Wada*

Department of Materials Chemistry, Ryukoku University, Seta, Otsu, 520-2194 Japan *Corresponding Author: twada@rins.ryukoku.ac.jp

There is a strong need for high performance electrooptic ceramics that can be used at a

reduced applied electric field in optical communications. Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT) transparent ceramics are among those with large electrooptic properties. However, a preparation of transparent ceramics usually requires a hot-press technique, which is not suitable for mass production. We have reported successful preparations of PMN-PT transparent ceramic by a cost-effective conventional (pressure-less) sintering [1, 2]. In the present study, Zn was partially substituted for Mg in 0.9Pb(Mg1/3Nb2/3)O3-0.1PbTiO3 ceramics, -and effects of the substitution on the crystal structure and the optical and electric properties were investigated.

0.9Pb((Mg1-xZnx)1/3Nb2/3)O3-0.1PbTiO3 (x=0-0.4) ceramics were prepared by the columbite precursor method. Powders of synthesized (Mg1-xZnx)Nb2O6, PbO and TiO2 were batched according to the general formula with excess 2 wt% PbO. Then, they were ball-milled and calcined at 780-880 oC for 4 h. The agglomerate was crushed and the calcined powder was ball-milled using a planetary ball mill (classic line P-7, Fritsch, Germany) with distilled water and stabilized zirconia balls with diameters of 3 mm. Green ceramics were uniaxially pressed at 70 MPa in a 10-mm-diameter die and cold isostatically pressed at 200 MPa. Green ceramics were sintered at 1240 - 1280oC for 15 h in an oxygen atmosphere. Density was measured by an immersion method. Structure characterization was performed by X-ray diffraction on polished surfaces of sintered ceramics. Optical transmission spectrum from 300 to 2000 nm was measured by ultraviolet-visible-near infrared (UV-vis-NIR) spectroscopy.

The X-ray diffraction patterns indicated formation of a perovskite phase with pseudo-cubic symmetry at x=0-0.4. The secondary phase of a pyrochlore phase was observed at x = 0.3 and 0.4. The relative density was 99.9, 98.8, 98.8, 97.3, 97.9% at x=0, 0.1, 0.2, 0.3, and 0.4, respectively. Figure 1 shows the appearance of the ceramics, which were transparent at x=0-0.2 while they were opaque and yellowish at x=0.3 and 0.4. Figure 2 shows the transmittance spectra of the 0.9Pb((Mg1-xZnx)1/3Nb2/3)O3-0.1PbTiO3 (x=0-0.4) ceramics. At x=0-0.2, the transmittance increased sharply from the wavelength of about 400 nm and reached 40-55% at 2000 nm. On the other hand, low transmittance was observed at x=0.3 and 0.4. The polarization – electric field response was relaxor-like at x=0. With increasing x from 0 to 0.2, the remanent polarization increased and the response became ferroelectric. At x=0.3 and 0.4, the response remained ferroelectric. These results suggest that the substitution of Zn changed a quadratic electrooptic effect to a linear one.

Fig. 1 Photographs of 0.9Pb((Mg1-xZnx)1/3Nb2/3)O3-0.1PbTiO3 ceramics with diameter of about 8mm and thickness of about 0.5 mm.

Fig. 2 Transmittance spectra of 0.9Pb((Mg1-xZnx)1/3Nb2/3)O3-0.1PbTiO3 ceramic with x=0.0, 0.1, 0.2, 0.3, and 0.4.

References [1] I. Fujii, R. Yoshida, T. Imai, S. Yamazoe, and T. Wada, J. Am. Ceram. Soc. 96, 3782 (2013). [2] I. Fujii, H. Ono, and T. Wada, J. Mater. Res. 29, 2260 (2014).

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Contrasting strain mechanisms in lead-free piezoelectric ceramics Neamul H Khansur,1,2,* John E Daniels,2 and Kyle G Webber1

1Department of Materials Science, University of Erlangen-Nürnberg, Erlangen 91058, Germany 2School of Materials Science and Engineering, UNSW Australia, 2052, Sydney, Australia

*Corresponding Author: neamul.khansur@fau.de Piezoelectric ceramics find a wide range of applications in advanced technological fields.

Most of the currently used electro-active ceramics contain lead (Pb). Environmental concerns and limitations in high temperature performances of lead based compositions have spurred the field of lead-free electroceramics research. Compositions based on bismuth sodium titanate (NBT), sodium potassium niobate (NKN), bismuth ferrite (BF) and barium titanate (BT) have long been considered as candidates to replace lead based electroceramics. Although lead-free compositions based on these systems exhibit piezoelectric properties for potential device application, further enhancement is required. To improve their properties, extensive knowledge of structure-property relationships, especially during the field-on condition is essential. Diffraction is a useful technique to highlight structure-property relationships (Figure 1). To understand the microscopic origin of strain in lead-free electroceramics several compositions based on NBT (e.g., Figure 2), NKN, BF and BT has been studied using in situ high energy x-ray diffraction. Their microscopic strain response has been elucidated under electric field. Both the intrinsic (lattice) and extrinsic (domain switching and/or phase transformation) strain contributions have been analysed for each system and have been correlated with their macroscopic properties. This comparative study of their strain responses will enable us to focus on some important aspects that are essential to improve electro-mechanical properties in future lead-free systems.

References [1] N. H. Khansur, M. Hinterstein, Z. Wang, C. Groh, W. Jo and J. E. Daniels, Applied Physics Letters 107 (24), 242902 (2015).

Figure 1 Field-induced structural change in a piezoelectric material. Intrinsic and extrinsic contributions can be highlighted from the diffraction profile.

Figure 2 Diffraction profile for NBT-BT in the (a) as-processed state and variation in 111 (b)and 200 (c) reflection under applied electric field.1 Electric-field-induced phase transformation to mixed phase state is apparent. Types of structural contributions present at the microscopic length scales in a mixed-phase composition have been reconciled by quantitative full pattern Rietveld refinements which incorporate texture analysis.

Internal Bias Fields in Ferroelectric HfO2 Thin Films and their Structural Origins T. Schenk,1,* M. Hoffmann,1 J. Ocker,1 M. Pešić,1 E. D. Grimley,2 X. Sang,2 J. M. LeBeau,2

T. Mikolajick,1,3 and U. Schroeder1 1NaMLab gGmbH, Noethnitzer Str. 64, Dresden D-01187, Germany

2Department of Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina 27695-7907, USA

3IHM TU Dresden, Noethnitzer Str. 64, Dresden D-01187, Germany *Corresponding Author: tony.schenk@namlab.com

When ferroelectricity in Si:HfO2 was first reported in 2011 [1], it was a major surprise

given the wealth of studies on hafnia and zirconia especially as so-called “high-k” dielectric for semiconductor technology. In the past years, the existence of a non-polar phase was experimentally verified [2,3] and together with theoretical work, stabilization mechanisms for this phase could be elucidated [4,5]. Moreover, the electric field cycling behavior of ferroelectric hafnia has emerged as one of the main topics of study [6,7]. This electric field cycling behavior [7] includes 1) wake-up, 2) fatigue and 3) a recently discovered split-up phenomenon. All three phenomena describe a change in the shape of the ferroelectric hysteresis and are therefore, highly relevant for applications such as ferroelectric memories [8]. From a more fundamental point of view, insights into the underlying physical mechanisms in this new ferroelectric are of interest.

Figure 1. a) Preisach plane with corresponding elemental hystereses (hysterons) illustrating

the meaning of the switching density plots obtained from FORC measurements. b) Switching density plot obtained after the cycling sequence shown in the inset.

Here, we present results of first-order reversal curve (FORC) measurements as they are

uniquely suited to verify the proposed model for the split-up phenomenon and scenarios for the wake-up effect. The FORC approach was used to study capacitors subjected to different sequences of field cycling treatment. A complex interplay of internal bias fields is found to govern both wake-up and the novel split-up phenomenon (Figure 1). Finally, structural changes within the capacitors are derived from a complementary approach of impedance spectroscopy and transmission electron microcopy, which explain the evolution of the internal bias fields found in the FORC measurements.

References [1] T. S. Böscke et al., Appl. Phys. Lett., 99, 112904 (2011) [2] X. Sang et al. Appl. Phys. Lett. 106, 162905 (2015) [3] T. Shimizu et al., Appl. Phys. Lett. 107, 032910 (2015) [4] R. Materlik, C. Künneth, A. Kersch, J. Appl. Phys., 117, 134109 (2015) [5] M. Hoffmann, et al., J. Appl. Phys., 118, 072006 (2015) [6] D. Zhou, et al., Appl. Phys. Lett., 103, 192904 (2013) [7] T. Schenk et al. ACS Appl. Mater. Interfaces, 6, 19744-19751 (2014) [8] J. F. Scott, Ferroelectric Memories, Springer-Verlag, Berlin (2000)

Local and mesoscale structural changes in BaTiO3−Bi(Zn0.5Ti0.5)O3 under electric-field or elevated temperature

Dong Hou1, *, Tedi-Marie Usher1, Natthaphon Raengthon2, Narit Triamnak2, David P. Cann2, Jennifer S. Forrester1, and Jacob L. Jones1

1 Materials Science and Engineering, North Carolina State University, Raleigh, USA 2 Materials Science, Oregon State University, Corvallis, USA

*Corresponding Author: dhou3@ncsu.edu

Solid solutions of barium titanate (BaTiO3) and bismuth zinc titanate Bi(Zn0.5Ti0.5)O3, BT-xBZT, exhibit anomalous dielectric and ferroelectric properties, which include high dielectric permittivity and large electrostriction coefficients under both high electric fields and high temperatures. Therefore, BT-xBZT has great potential for applications in electromechanical actuators, transducers, and high energy density capacitors.1 Previously, the crystallographic structure of BT-xBZT was studied by conventional X-ray diffraction at room temperature and the electric properties (e.g. permittivity, energy density, and dielectric relaxation) have been analyzed.2 However, to our knowledge, the fundamental mechanisms behind the anomalous dielectric properties at elevated temperature or under the application of electric-field have yet to be established. Since the dielectric properties depend heavily upon the crystallographic structure, this research uses an in situ X-ray total scattering technique to detect the local and mesoscale structural changes as a function of composition, temperature, or applied electric-field, and furthermore, to reveal the structural origin of these properties in BT-xBZT.

In order to establish the relationship between temperature-induced structural changes and dielectric properties, we introduced in situ atomic pair distribution functions (PDFs), which are determined from X-ray total scattering, to reveal structural changes over different length scales during in situ heating of BT-xBZT from 25°C to 500°C. Fig. 1(a) shows the stack of PDF patterns of BT-0.06BZT at different temperatures as an example. With increasing temperature, peaks shift to the right, suggesting lattice expansion; peak broadening was also observed due to increased thermal vibration of atoms at elevated temperatures. By using whole PDF pattern fitting and boxcar fitting methods, we found all four compositions exhibit increased local tetragonal distortion compared to their average structures. Fig. 1(b) shows the lattice parameters as a function of temperature. The distinct behaviors of lattice changes in BZT≥0.10 and BZT<0.10 compositions may suggest two different mechanisms in particular BZT concentration regions. The gradual structural changes with temperature might contribute to the broad permittivity distribution in BZT≥0.10 samples.

The macroscopic functional properties of many materials result from atomic scale changes to the structure caused by an applied stimulus. Consequently, studying the atomic-scale response of dielectrics to electric fields is crucial.3 In this study, we developed a novel in situ PDF approach (including experimental setup and characterization methods) that reveals local scale changes in polycrystalline dielectrics under electric fields. Our preliminary analysis shows an increase in atom-atom distances parallel to the electric field in BT-xBZT, which is attributed to piezoelectric lattice strain. Moreover, BaTiO3 exhibits a gradual variation at local scale with electric field, while the responses are weaker and more diffusive when alloying with more BZT. References 1. Zeb, A. & Milne, S. J. J. Mater. Sci. Mater. Electron. 26, 9243–9255 (2015). 2. Bootchanont, A. et al. Ceram. Int. 40, 14555–14562 (2014). 3. Usher, T.-M. et al., Sci. Rep. 5, 14678 (2015).

Figure 1 PDF patterns of BT-6BZT at various temperatures (a) and lattice parameters as a function of temperature for BT-xBZT (b)

Thermal Conduction in Ferroelectric Thin Films: Size, Composition, and Domain Effects

J.F. Ihlefeld,1,* B.M. Foley,2 D.A. Scrymgeour,1 J.R. Michael, 1B.B. McKenzie,1 D.L. Medlin,1 E.A. Paisley,1 B.F. Donovan,2 T. Chavez,1 C. DiAntonio,1 M. Wallace,3 R.L.

Johnson,1 S. Trolier-McKinstry,3 P. Ryan,4 J-P. Maria,5 and P.E. Hopkins2

1Sandia National Laboratories, P.O. Box 5800, M.S. 1069, Albuquerque, New Mexico, USA

2University of Virginia, 122 Engineer’s Way, Charlottesville, Virginia, USA 3The Pennsylvania State University, University Park, Pennsylvania, USA

4Advanced Photon Source, Argonne National Laboratory, Lemont, Illinois, USA 5North Carolina State University, Raleigh, North Carolina, USA

*Corresponding Author: jihlefe@sandia.gov Thermal conduction in ferroelectrics is a topic that has received periodic interest for over 60

years. Owing to recent advances in thermal conductivity measurement technologies, the ability to characterize thin film properties has only recently been made possible. In this talk we will discuss the effects three features on thermal conduction in ferroelectric thin films: grain size, composition, and domains walls. Materials highlighted will include BaTiO3 and Pb(Zr,Ti)O3; Pb(Zr,Ti)O3; and BiFeO3 and Pb(Zr,Ti)O3, respectively. It will be shown that grain size scaling in BaTiO3 leads a filtering of long wavelength phonons,[1] resulting in substantial reductions in thermal conductivity compared to bulk counterparts. Changing composition in PZT reveals conventional alloy effects of reduced permittivity for non-end-member compositions, but also reduced thermal conduction in antiferroelectric compositions, which will be related to the complex phonon dispersion in these materials. Finally, owing to domain size scaling effects with reduced crystal dimensions, we will show how domain walls can scatter phonons at room temperature and that simple, voltage-actuated, and fast thermal switches may be prepared using ferroelectric films – a phenomena that has eluded the thermal transport community to date.[2] An ability to decrease thermal conductivity in mechanically clamped structures and increase conduction in strain-released structures will be demonstrated. Sandia National Laboratories is a multiprogram laboratory operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Company, for the United States Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

Figure 1. Thermal conductivity vs. (left) BaTiO3 grain size, (middle) PZT composition, and (right) time for PZT while cycling applied voltage. References [1] B. F. Donovan, B. M. Foley, J. F. Ihlefeld, J.-P. Maria, P. E. Hopkins, Appl. Phys. Lett. 2014, 105, 082907. [2] J. F. Ihlefeld, B. M. Foley, D. A. Scrymgeour, J. R. Michael, B. B. McKenzie, D. L. Medlin, M. Wallace, S. Trolier-McKinstry, P. E. Hopkins, Nano Lett. 2015, 15, 1791.

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Charge-based Deep Level Transient Spectroscopy Characterization of Acceptor-doped BaTiO3 Dielectric Ceramic for Capacitor

and Its Insulation Degradation Behavior T. Okamoto1,* J. Long2, J. Stitt2, R. H. T. Wilke2, A. Ando1, and C. A. Randall2

1 Murata Manufacturing Co., Ltd., 10-1 Higashikotari 1-chome, Nagaokakyo, Kyoto, Japan 2 The Pennsylvania State University, Millennium Science Complex, University Park, PA, USA

*Corresponding Author: okamoto_takafumi@murata.com Doping multilayer capacitors based on BaTiO3 is a key to engineering their performance for

both temperature dependent properties and reliability [1, 2]. There have been studies on time dependent failure on the viewpoint how/where it progresses, such as using KFM/TEM, but little is known on transient changes to dopant defects under high bias prior to time dependent breakdown processes. To investigate them more completely, we are considering deep level transient spectroscopy (DLTS). This is a widely used process for characterizing trap levels in depletion layers in semiconductors, but could possibly be used in BaTiO3 based dielectrics. We perform DLTS and directly analyze the relaxation behaviors of induced electric charges by pulse waves [3, 4]. Our charge-based DLTS (Q-DLTS) has successfully detected several trap levels in acceptor-doped BaTiO3 dielectric ceramic and their properties were estimated quantitatively.

As one of the representative cases, the DLTS signals from Mg doped BaTiO3 dielectric ceramic plate, which was sintered in reducing condition, are shown in Figure 1, and clear peaks have been obtained on this sample around 260-320 K upon each rate window condition. Regarding this case, it is better for fitting with experimental data to use two Gaussian functions. With the Arrhenius plot from these peaks, the two of estimated trap properties are 0.14 eV (Trap A) and 0.60 eV (Trap B). It is also observed that this peak for Trap B has been disappearing through degradation under high temperature and high electric field. That indicates that this possible transformation of the deep trap is strongly linked to the increase of leakage current in this BaTiO3.

Our study has been succeeded to estimate the trap properties of acceptor doped BaTiO3 dielectric and discussed the precise characterizations of these traps and local electronic states. That has shown Q-DLTS as the promising method for the characterization of these materials. This method will be useful for disclosing new aspects about insulation degradation or dielectric breakdown of BaTiO3 based dielectrics doped with several acceptor impurities.

Figure 1. The DLTS signals of the Mg doped BaTiO3 dielectric ceramic at several rate window conditions and the representative peak fit drawn with two Gaussians

References [1] T. Okamoto et al., Appl. Phys. Lett., 98, 072905 (2011). [2] K. Suzuki et al., J. Appl. Phys., 113, 064103 (2013). [3] D. Barančok et al., Phys. Stat. Sol., 172, 519 (1999). [4] T. Okamoto et al., Proceedings of 16th US-Japan Seminar on Dielectric and Piezoelectric Materials, pp. 112-115, Raleigh, NC, USA, 2013.

Pb(In1/2Nb1/2)-Pb(Mg1/3Nb2/3)-PbTiO3 single crystal monomorph with perpendicular electrode for sensing and energy harvesting

Ming Ma,1,* Zhenrong Li,1 Song Xia,1 Zhuo Xu,1 Xi Yao1

1Electronic Materials Research Laboratory, Key Laboratory of Education Ministry; International Center for Dielectric Research, Xi’an Jiaotong University, Xi’an 710049, China

*Corresponding Author: mamingcl@xjtu.edu.cn

Piezoelectric monomorph, which has only one element, is one kind of potential structure for

piezoelectric applications in some extreme conditions. However the traditional parallel electrode

connection is not effective for sensing and energy harvesting because of the restriction of the

strain neutral layer. In this paper, the perpendicular electrode connections were used to make the

monomorph avoid the restriction of the strain neutral layer. And Pb(In1/2Nb1/2)-Pb(Mg1/3Nb2/3)-

PbTiO3 single crystal monomorph with perpendicular electrodes was studied. By comparing sev-

en forms of perpendicular electrode connections with the traditional parallel electrode connection,

the whole superposed perpendicular electrode connection is considered as the optimal output

way for the monomorph. The 27.2V peak to peak voltage in open circuit and the 71.5μW maxi-

mum power with the matching resistance at the resonance frequency can be produced by the

whole superposed perpendicular electrode connection, which are much more than 3.2V and

1.5μW that produced by the parallel electrode connection.

Enhanced energy storage and dielectric properties of BaTiO3/BaTiO3@SiO2 layered ceramics

Qibin Yuan1, Yifei Wang1, Hong Wang1, * 1School of Electronic and Information Engineering and State Key Laboratory for Mechanical

Behavior of Materials, Xi’an Jiaotong University, Xi’an, 710049, China

*Corresponding Author: hwang@mail.xjtu.edu.cn

Dielectrics have been the important and major enabler for advanced electronics and electrical power system due to their inherent advantages, such as high power density, high volumetric specific energy, long service life and short charging time. [1] However, their energy densities are still very low compared with other energy storage materials and improving energy density would be an be essential to realize their full potential in electrical pulse power systems and power electronics. The layered structural BaTiO3/BaTiO3@SiO2 (BTBS) ceramics have been successfully prepared by tape-casting and lamination. BaTiO3 (BT) ceramic has high dielectric constant and low breakdown strength while BaTiO3@SiO2 (BS) ceramic has low dielectric constant and high breakdown strength. Their complementary advantages could be combined by the layered structure to get a superimposed effect to improve energy storage properties.

Figure 1. P-E loops of BS3 ceramics, BTBS3 layered ceramic. The inset displays P-E loops of BT ceramic. (The 3.0 wt% SiO2 coated BT ceramic is abbreviated as BS3, the layered ceramic

with 3.0 wt% SiO2 in BS layer is abbreviated as BTBS3)

It can be seen from figure 1 that the BSBT3 layered ceramic has a higher polarization at the same electric field compared to BS3 ceramic and can obtain much higher breakdown strength. The optimization of dielectric constant or polarization is achieved through the diluting effect of the layered structure on the low dielectric constant of the BS layer. And the enhancement of the breakdown strength of the layered ceramics depends on the interface barrier effect and the optimal electric field distribution by the capacitive voltage divider. [2, 3] As a result, the maximum energy density of 1.8 J/cm3 and the energy efficiency of 71.5 % are obtained at a breakdown strength of ~290 kV/cm in the BBTS3 ceramic, indicating that the BTBS layered ceramics may be a promising candidate for integration into future power electronics applications. References [1] G. R. Love, J. Am. Ceram. Soc., 73, 323-328 (1990). [2] D. P. Agoris, I. Vitellas, O. S. Gefle, S. M. Lebedev , Y. P. Pokholkov, J. Phys. D: Appl.

Phys., 34, 3485–3491 (2001). [3] L. Flandin, L. Vouyovitch1, A. Beroual2, J-L Bessede and N. D. Alberola, J. Phys. D: Appl. Phys.

38, 144–155 (2005).

The phase transition of K1-xNaxNbO3 study by First-Principles

Dong Yang, Lingling Wei, and Zupei Yang* School of Materials Science and Engineering, Shaanxi Normal University,

No. 620 West Chang'an Avenue, Xi'an, P. R. China *Corresponding Author: yangzp@snnu.edu.cn

Abstract: The first principles calculations based on Density Functional Theory

(DFT) have been used to determine the structural, phase transition, and electronic properties of K1-xNaxNbO3 (KNN) structure. The augmented p Line wave plus local orbitals (APW-LO) method and the supercell method are used in the calculation for the KNN solid solutions. We found that the Na content of KNN was gradually increased when the tetragonal phase transformation was carried out. The results show that the phase transition from the strong hybridization between the Nb atom and the O atom, the substitution of the Na atom introduces the A-site enhances the hybridization of the Nb-O atoms and then reduce the band length of the Nb-O, which bring a variation of lattice constant, which may be the main reason for the phase transition of K1-xNaxNbO3

Solid Solutions. The calculated results show the same trend as the experiment results.

Figure 1 Structures of (a) O-phase and (b) T-phase KNN.

References: [1] H. Tian, C. P. Hu, X. D. Meng, P. Tan, Z. X. Zhou, J. Li, and B. Yang, Cryst. Growth Des. 15, 1180-1185 (2015). [2] Y. Saito, H. Takao, T. Tani, T. Nonoyama, K. Takatori, T. Homma, T. Nagaya, and M. Nakamura, Nature (London), 432, 84–87 (2004). [3] H. Tian, , C. P. Hu, Q. Z. Chen, Z. X. Zhou, Materials Letters, 68, 14-16 (2012). [4] G. Z. Zang, J. F. Wang, H. C. Chen, W. B. Su, C. M. Wang, P. Qi, B. M. Ming, J. Du, L. M. Zheng, S. J. Zhang, and T. R. Shrout, Appl. Phys. Lett. 88, 212908 (2006).

Spontaneous Relaxor to Normal Ferroelectric Phase Transition in (Bi1/2K1/2)TiO3 Lead-free Piezoelectric Ceramics

M. Hagiwara,1,* Y. Ehara,2 and S. Fujihara1 1Department of Applied Chemistry, Keio University, 3-14-1 Hiyoshi, Kohoku-ku,

Yokohama 223-8522, Japan 2Institute of Materials Science, Technische Universität Darmstadt, Alarich-Weiss-Straße 2,

Darmstadt 64287, Germany *Corresponding Author: hagiwara@applc.keio.ac.jp

Bismuth potassium titanate (Bi1/2K1/2)TiO3 (BKT) is a ferroelectric with relatively high

tetragonal lattice distortion (c/a ~ 1.02) at room temperature compared with BaTiO3 (c/a ~ 1.01). BKT has been attracting increasing attention as a lead-free piezoelectric material for high-temperature actuator applications owing to its high depolarization temperature around 300 ○C [1, 2]. However, phase transition behaviors and depolarization mechanisms of BKT are less well understood compared with those of its structural analog (Bi1/2Na1/2)TiO3. This is mainly due to the difficulty in fabricating dense and phase-pure ceramic samples of BKT caused by its low melting point (~1070 ○C) and the high volatility of Bi and K elements. In the present work, we fabricated high-quality BKT ceramic samples using hydrothermally derived fine powders and studied their phase transition behaviors by means of dielectric measurement.

BKT fine powder with a particle size around 200 nm was synthesized by a hydrothermal process using TiO2, Bi(OH)3, and KOH as metal sources [3]. Dense BKT ceramics with relative density > 95% were obtained by sintering the hydrothermal powder at 1060 ○C. The grain size of the sintered ceramics could be controlled between 0.2 and 1.0 μm by prolonging the sintering time. Figure 1 shows the temperature dependence of a BKT ceramic sample with a grain size about 1 μm. A dielectric anomaly is observed around 300 ○C with a strong thermal hysteresis. The temperature for dielectric maximum (Tm) shifts toward higher temperatures with increasing the measuring frequency. The results indicate that the temperature induced transition between high-temperature relaxor (R) phase and low-temperature normal ferroelectric (nFE) phase occurs upon cooling/heating. Depolarization current after poling treatment reveals that the depolarization of BKT occurs at once at the temperature of the nFE to R phase transition (Figure 2). We also found that the transition from the R phase to nFE phase is inhibited in finer-grained ceramics, probably due to the influence of compressive stress from grain boundaries. In the presentation, we will also discuss the effect of biasing electric field on the R-nFE transition.

References [1] Y. Hiruma, R. Aoyagi, H. Nagata, and T. Takenaka, Jpn. J. Appl. Phys., 44, 5040 (2005). [2] H. Nagata, K. Tabuchi, and T. Takenaka, Jpn. J. Appl. Phys., 52, 09KD05 (2013). [3] M. Hagiwara and S. Fujihara, J. Mater. Sci., 50, 5970 (2015).

0

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Figure 1. Temperature dependence of dielectric permittivity measured at 1, 10, and 100 kHz.

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Temperature, T/°C Figure 2. Temperature dependence of remanent polarization calculated from depolarization current upon heating after a poling treatment.

Tunability and piezoelectric properties of Ba1-xCaxTi1-yZryO3 thin films C.J.M. Daumont1, Q. Simon2, S. Payan2, P. Gardes3, P. Poveda3, B. Negulescu1,

M. Maglione2 and J. Wolfman1*

1 Lab. GREMAN, UMR7347 CNRS, Université François Rabelais de Tours, France

2 ICMCB, UPR9048 CNRS, Université de Bordeaux, France

3 STMicroelectronics, Tours, France

*e-mail: wolfman@univ-tours.fr

Tunable ferroelectric capacitors, which exhibit a decrease of the dielectric permittivity (ε)

under electric field, are widely used in electronics for RF tunable applications (e.g. antenna impedance matching). Current tunable devices use barium strontium titanate (BST) dielectric. Improving on BST performances is one key for a tighter energy management. For this purpose, we chose to investigate the BaTiO3-CaTiO3-BaZrO3 ternary phase diagram where morphotropic phase boundaries (MPB) are expected. Indeed, increased dielectric, piezoelectric and ferroelectric properties have been reported in (1-x)BaTi0.8Zr0.2O3-xBa0.7Ca0.3TiO3 (BCTZ) ceramics in the vicinity of a MPB for x=0.5 [1]. More recently, thin films of BCTZ with composition at the MPB have shown interesting tuning ratios of 5/1 under a field of 300kV/cm [2].

We report here on libraries of BCTZ thin films deposited on IrO2/SiO2/Si substrates using combinatorial pulsed laser deposition (CPLD) allowing for gradients of composition on one sample [3]. The dielectric properties of 8 samples, each one containing 480 capacitors (40 different compositions with 12 capacitors per composition), were statistically investigated. Effective piezoelectric coefficient d33 were also measured across the ternary phase diagram by dual beam laser interferometer.

Figure 1. Effective d33 versus composition for one BCTZ library (a). Contour map of the effective d33 versus compositions in the ternary phase diagram (b).

We show that tunability >70% can be obtained under an electric field of 250kV/cm. Calcium

and zirconium contents influence the breakdown voltage in the same way, while Ca is beneficial to tunability and Zr to low losses. Thus lowest dielectric losses and maximum tunabilities are not obtained for a single composition and call for compromise. Rapid variation of the d33 versus composition were observed, reminiscent of d33 behavior across MPBs. Composition with effective d33 of 35 pm/V, about 2/3 of effective d33 for PZT thin films of the same thickness (48 pm/V @ 130 nm) [4], were identified. Piezoelectric and dielectric properties versus temperature are being investigated and will be reported. Finally we show that CPLD is a powerful screening tool to identify the best compromise depending on the needs (high tunability at low voltage, low dielectric losses, high d33...). References [1] W. Liu et X. and Ren, Phys. Rev. Let. 103, 257602 (2009). [2] A. Piorra, P. A., H. Kohlstedt, M. Wuttig and E. Quandt, J. Appl. Phys. 109, 104101 (2011). [3] G. Liu et al., J. Appl. Phys. 108, 114108 (2010).

[4] Y. Bastani et al., J. Appl. Phys. 109, 014115 (2011).

Over-poling Study of PMN-PT and PIN-PMN-PT Crystal Grown by Vertical Gradient Freeze Method

Zibo Jiang1 1Innovia Materials (Shanghai) Co., Ltd

*Corresponding Author: jiang@innoviamaterials.com Lead magnesium niobate – lead titanate (PMN-PT) crystal was grown by Vertical Gradient

Freeze (VGF) method. Poling reactions of PMN-28%PT and PMN-32%PT were studied. Different poling voltages were used to pole along [001] direction, the resultant impedance, dielectric constant, electromechanical coupling coefficient and dielectric loss were recorded. It is evident that poling of PMN-28%PT saturates at around 320 kV/mm and poling of PMN-32%PT saturates at around 200 kV/mm. As poling voltage increases, over-poling starts to manifest at around 1400 V/mm for PMN-28%PT (Figure 1) and 1000 V/mm for PMN-30%PT. Previous works attributed over-poling to field-induced phase change from rhombohedra to monoclinic or tetragonal phase, which is to be confirmed by observing permittivity in zero-field heating environment.

Several methods were deployed in attempt to recover over-poling damages, including heating the crystals above Curie temperature and reverse poling. However, such attempts failed to recover key properties such as impedance (Figure 1). It is therefore concluded that the over-poling of PMN-PT may be irreversible in transducer engineering practices and should be carefully avoided.

Similar study is to be extended to the tertiary crystal system PIN-PMN-PT.

Figure 1. Plot of impedance vs. frequency after poling at different voltages for (001) PMN-

28%PT plates, demonstrating the crystal is over-poled at 1400 V/mm along [001], and that such damage cannot be recovered by heating the crystal above Curie temperature.

References [1] A. A. Bokov and Z.-G. Ye, Physics Review B 66, 094112 (2002). [2] Z. Jiang, 2015 Joint IEEE International Symposium on the Applications of Ferroelectric, International Symposium on Integrated Functionalities and Piezoelectric Force Microscopy Workshop (ISAF/ISIF/PFM), Singapore, 56-59 (2015). [3] Y. Lu et al., Applied Physics Letters 78, 3109 (2001). [4] Y. Lu et al., Applied Physics Letters 80, 1918 (2002). [5] K.K. Rajan et al., Sensors and Actuators A 133 (2007) 110–116. [6] M. Shanthi et al., Applied Physics Letters 86, 262908 (2005). [7] C.-S. Tu et al., Physics Review B 70, 220103 (2004).

Preparation of Freestanding PMN-PT Films on Si-based Templates for Electrocaloric Studies

M. Mietschke,1,3 S. Engelhardt,1,3 C. Molin,2 S. Gebhardt,2 Y. Zhang,1 F. Ding,1 P. Chekhonin,1,3 S. Abel,4 J. Fompeyrine,4 S. Fähler,1 K. Nielsch1,3 and R. Hühne1,*

1IFW Dresden, Helmholtzstraße 20, 01069 Dresden, Germany 2 Department of Smart Materials and Systems, Fraunhofer Institute for Ceramic Technologies

and Systems, Winterbergstraße 28, D-01277 Dresden, Germany 3 Technische Universität Dresden, Helmholtzstraße 7, D-01069 Dresden, Germany

4IBM Research GmbH, Säumerstrasse 4, 8803 Rüschlikon, Switzerland *Corresponding Author: r.huehne@ifw-dresden.de

Nowadays, significant efforts are directed to the development of energy-efficient cooling

technologies suitable for industrial as well as private applications. One emerging technology is the use of solid state cooling with electrocaloric (EC) materials. These materials show a remarkable temperature change by applying an electric field adiabatically. Prominent examples are Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT) compounds, which are typically used for high performance actuator applications due to its outstanding piezoelectric properties for compositions close to the morphotropic phase boundary. As the structural and functional properties of these materials are well-known, they might also serve as a suitable model system to study the interplay between microstructure and EC properties. For this purpose, a lower PT content is used to get a high EC effect over a broad temperature range close to room temperature as shown in literature before. Additionally, epitaxial films are a useful tool to analyze this correlation in more detail in order to optimize the performance of these materials. However, a crucial point to determine the EC properties directly is to minimize the influence of the heat capacity of the substrate, which might be realized by releasing the PMN-PT film from the template.

Therefore, epitaxial 0.9PMN-0.1PT films were grown by pulsed laser deposition on (001)-oriented STO buffered Si wafers as well on SrTiO3 (STO) single crystalline substrates using an epitaxial La0.7Sr0.3Co3 buffer as bottom electrode and additional Au top electrodes on the surface of the PMN-PT layer. The particular PT content was chosen to get a ferroelectric phase transition close to room temperature making these materials suitable for solid state cooling applications under ambient conditions. The PMN-PT film on Si was released from the substrate by selective wet etching via channels from the top side.

The structural properties of the grown samples are studied by high resolution x-ray diffraction, atomic force microscopy and transmission electron microscopy. The investigations revealed a pyrochlore-free, homogeneous and smooth epitaxial growth on both substrates. Dielectric properties as the relative permittivity and the dielectric loss are determined in dependence of temperature and frequency to verify the ferroelectric quality. The temperature of maximum permittivity Tm was about 30°C indicating the desired phase transition close to room temperature. Temperature and frequency dependent measurements showed a typical polarization hysteresis for both samples. Piezoresponse force microscopy was used to study the local ferroelectric properties of the PMN-PT on Si in the as-deposited as well as in the released state. A similar phase shift was observed for both states. Finally, first results for electrocaloric measurements will be presented. This work is supported by DFG priority program 1599 “Ferroic cooling”.

Hydrothermal Deposition of (Bi1/2K1/2)TiO3 Films on Titanium Metal Substrates R. Sakurai, M. Hagiwara,* and S. Fujihara

Department of Applied Chemistry, Faculty of Science and Technology, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223-8522, Japan

*Corresponding Author: hagiwara@applc.keio.ac.jp Vibration energy harvesting (VEH) devices using piezoelectric materials has been attracted

increasing attention toward the realization of battery-free sensor networks. In this work, we have focused on bismuth potassium titanate (Bi1/2K1/2)TiO3 (BKT), a perovskite ferroelectric with a relatively high piezoelectric coefficient (d33 ~ 120 pC/N) and low dielectric permittivity (εr ~ 500), as a candidate material for VEH applications. For VEH applications, it is desired that the piezoelectric film is deposited on a metal substrate to achieve large displacement and high mechanical strength. Here we report the deposition of BKT films on Ti metal substrates by a hydrothermal process.

In the hydrothermal process conducted in this work, Ti substrates also act as the Ti source of BKT film. Thus, the surface state of Ti substrates should be important factor to control the morphology, thickness, and electrical properties of the resulting films. For this reason, we used two kinds of Ti substrates: bare Ti substrate and the one thermally oxidized at 700 ºC for 1 h in air. A substrate was placed in 50 ml autoclave and then 12 M KOH aqueous solution containing a certain amount of Bi2O3 was added. The autoclave was heated at 200 ºC for 4 h. Figure 1 shows XRD patterns of the films obtained using the bare and thermally-oxidized Ti substrates. We have successfully obtained a film of the single-phase tetragonal BKT by using the bare Ti substrate. On the other hand, the film prepared using the thermally-oxidized Ti substrate shows the diffraction peaks from metal Bi in addition to those from BKT. The film deposited on the bare Ti substrate is composed of densely packed cubic particles with a size about 5 µm (Figure 2(a)). The cross-sectional SEM image (Figure 2(b)) shows the thickness of the film is 5-15 µm. We also found that the films prepared using the thermally-oxidized Ti substrates is composed of much larger BKT particles with a size over 15 µm. From these results, it is found that the phase purity and morphology of BKT films is highly affected by the surface condition of Ti substrates. Bare Ti substrate dissolves into the solution in association with the redox reaction with the dissolved oxygen, whereas TiO2 layer of the thermally-oxidized Ti substrate dissolves without the redox reaction. This difference of the dissolution process of the Ti sources is considered to affect supersaturation of BKT under the hydrothermal reaction, resulting in the morphology change of BKT films.

References [1] M. Hagiwara and S. Fujihara, Jpn. J. Appl. Phys, 54, 10ND10 (2015). [2] J. König and D. Suvorov, J. Eur. Ceram. Soc., 35, 2791 (2015).

Figure 1. XRD patterns of the films prepared using bare and thermally-oxidized Ti substrates.

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Fabrication of Zr-substituted (Bi1/2K1/2)TiO3 Lead-free Piezoelectric Ceramics via a Hydrothermal Process

M. Ito, M. Hagiwara,* and S. Fujihara Department of Applied Chemistry, Faculty of Science and Technology, Keio University, 3-14-1

Hiyoshi, Kohoku-ku, Yokohama 223-8522, Japan *Corresponding Author: hagiwara@applc.keio.ac.jp

Bismuth potassium titanate (Bi1/2K1/2)TiO3 (BKT), a perovskite ferroelectric with a

tetragonal symmetry at room temperature, has been regarded as a promising lead-free piezoelectric material owing to its relatively large tetragonal lattice distortion (a/c ~ 1.02) and high depolarization temperature around 300 ºC [1]. By analogy with the well-known Pb(Zr, Ti)O3 system, the substitution of Ti4+ ion in BKT by other tetravalent cations is expected to improve the ferroelectric and piezoelectric properties. However, only a limited number of studies have been conducted on the B-site substitution of BKT, which is mainly due to synthesis problems caused by the volatility of Bi and K elements and the poor sinterability of BKT. In this study, we fabricated dense ceramics of Zr-substituted BKT using hydrothermally derived fine powders.

Powders of Zr-substituted BKT with nominal compositions of (Bi1/2K1/2)(ZrxTi1-x)O3 (x = 0, 0.5, and 1.0) were synthesized by a hydrothermal process using alkoxides as Ti and Zr sources. To ensure the chemical homogeneity of the B-site cations, Ti[OCH2(CH3)2]4 and Zr[OCH2CH2CH3]4 were firstly dissolved in ethanol and mixed well, and then added dropwise to water to form white suspension of TiO2-ZrO2 sol. The resulting suspension added with a certain amount of KOH was heated to 160 ºC, and then held at 110 ºC for 6 h under stirring at 400 rpm. This process successfully provided the single-phase perovskite powders. On the other hand, we found that the hydrothermal reaction using powders of TiO2 and ZrO2 as raw materials does not provide the single phase. The particle sizes of the obtained powders were all around 300 nm as shown in Figure 1 for 10 mol% Zr-substituted BKT. Owing to the fine particle sizes, all the powders were almost fully densified (relative density > 95%) by the sintering at temperatures below their melting points. The XRD patterns of the sintered samples (Figure 2) show peaks shifts toward lower angle with increasing the Zr content, indicating the crystal lattice expansion by the incorporation of Zr4+ ion into B site. It is also found that the Zr substitution decreases the tetragonal distortion of BKT, and consequently, the 10 mol% Zr-substituted sample shows a cubic symmetry. The electrical properties of these samples are now under investigation.

Reference [1] Y. Hiruma, R. Aoyagi, H. Nagata, and T. Takenaka, Jpn. J. Appl. Phys., 44, 5040 (2005).

Figure 1. FE-SEM image of the 10 mol% Zr-substituted BKT powder.

200 nm

Figure 2. XRD patterns for Zr-substituted BKT ceramics with Zr contents of 0, 5, and 10 mol%.

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Structure, dielectric properties and energy storage performance of barium strontium titanate thin films prepared by spin-coating technique

C.L. Diao, H. Hao, M.H. Cao, Z.H. Yao, and H.X. Liu* State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan

University of Technology, LuoShi Road 122, Wuhan, China *Corresponding Author: lhxhp@whut.edu.cn (H.X. Liu)

Paraelectric barium strontium titanate Ba0.4Sr0.6TiO3 (BST) ceramics have potential

applications in the field of pulse power devices due to their outstanding performance, such as high dielectric constant, low loss, excellent mechanical and thermal stability, et al [1]. Compared with polymer, the breakdown strength (BDS) and energy storage density of ceramic capacitors are low. Meanwhile, with the integration and miniaturization of electric devices, thin films for energy storage have attracted much attention because of their high BDS [2]. However, few reports about the energy storage of BST thin films are discussed in the literature.

In this work, the BST thin films were deposited on Pt/TiO2/SiO2/Si or LaNiO3/Si substrates by spin-coating technique. The pyrolysis and crystallization temperature were determined based on the TG-DSC curves of BST dry gel. The LNO film was used as bottom electrode, which was prepared on Si(100) substrate by a modified metalorganic decomposition technique [3]. Au top electrodes (0.3mm diameter) were deposited through a shadow mask by e-beam evaporation. The electrical properties were measured using Agilent 4294A impedance analyzer and Radiant precision workstation.

Figure 1. Surfaces SEM images of BST thin films deposited on a) LNO and b) Pt substrates; c) XRD patterns of BST thin films deposited on LNO and Pt, and LNO thin films deposited on Si

Scanning electron microscope (SEM) shows that the surfaces morphology of both films was

smooth and crack-free. Dense and uniform grains were observed without any obvious secondary phase. A typical cubic perovskite structure with space group mPm3 was identified by X-ray diffraction (XRD) analysis and no impurity peak was detected, which is consistent with the results of SEM. The peaks of LNO films are wide with low intensity for its smaller grains. The effects of bottom electrodes on dielectric, ferroelectric and energy storage properties of BST films were investigated. The results shows that the dielectric constant of BST/Pt film is a little higher than that of BST/LNO film, and the dielectric loss of both films is very low, <5‰. A butterfly loops with good dielectric tunability was observed in the capacitance-voltage (C-V) curve of BST/LNO film. The DC leakage current densities at 100kV/cm are ~9.3×10-9A/cm2 and ~1.0×10-8A/cm2 for BST/LNO and BST/Pt films, respectively. The P-E loops and energy storage performance of both films are similar. It was indicated that BST/LNO thin film can be applied as a cost-effctive and environment-friendly capacitor for high-power energy storage. References

[1] Z. Song, H.X. Liu, S.J. Zhang, Z.J. Wang, Y.T. Shi, H. Hao, M.H. Cao, Z.H. Yao, Z.Y. Yu, Journal of the European Ceramic Society, 34, 1209–1217 (2014) [2] P. Hu, Y. Shen, Y. Guan, X. Zhang , Y. Lin, Q. Zhang, C.W. Nan, Advanced Functional Materials, 24, 3172-3178 (2014) [3] X.J. Meng, J.L. Sun, J. Yu, H.J.Ye, Applied Surface Science,171, 68-30 (2001)

c)

Piezoelectret-based Flexible Film-Transducers for Wearable Devices X. Ma1, P. Fang,2,3 and X. Zhang1,*

1Shanghai Key Laboratory of Special Artificial Microstructure and Technology & School of Physics Science and Engineering, Tongji University, Siping Road 1239, Shanghai, China

2Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, China 3National Engineering Research Center for Tissue Regeneration and Reconstruction, School of Materials Science and Engineering, South China University of Technology, Guangzhou, China

*Xiaoqing Zhang: x.zhang@tongji.edu.cn Piezoelectrets were prepared by the microstructure modification and corona charging of

polypropylene (PP) foam sheets, and thereafter film-transducers based on such fabricated PP piezoelectret films, with a specific designed fold-structure, were developed. The electromechanical performances of the as-prepared transducers were investigated, and possible applications especially in wearable devices were discussed.

Figure 1. Sensitivity of film-transducers as a function of frequency.

Figure 2. A typical signal segment of human pulse recorded at wrist with a film-transducer.

Electromechanical performances including the complex dielectric spectra, frequency

response, thermal stability, humidity sustainability, and fatigue property of the film-transducer samples were investigated. The experimental results show that the typical capacitance and impedance of the film-transducers were 43.7 PF and 3.6 MΩ at 1 kHz, respectively. Piezoelectric sensitivity up to 600 PC/g was achieved, but after annealing treatments at temperatures of 50, 70, and 90 oC for 24 hours, 54%, 30%, and 13% of the initial values were remained, respectively. The film-transducers had a good performance in high-humidity environment, and their sensitivity decreased to about 70% of the initial values in a humidity of 98% after 37 days. In the fatigue test, about 70% of the initial sensitivity was still retained after 1.5 million cycles of operation with a dynamic force of 220 N applied to the samples. The performance assessments demonstrated that the PP piezoelectret film-transducers would have promising application potentials in wearable devices, which were also preliminarily exploited in this work.

References [1] S. Bauer, R. Gerhard-Multhaupt, Physics Today, 57(2), 37-44 (2004) [2] X. Zhang, J. Hillenbrand and G. M. Sessler, Appl. Phys. Lett., 85, 1226-1228 (2004) [3] P. Fang et al., Measurement Science and Technology, 23(3), 035604 (2012)

Preparation of (Bi0.5Na0.5)TiO3-BaTiO3 ceramics with Hexagonal BaTiO3 powders and Properties evaluation

M. S. Kim1, R. Itou1, T. S. Suzuki2, T. Uchikoshi2 and S. Wada1,*

1Interdisciplinary Graduate School of Medicine and Engineering, University of Yamanashi, 4-4-37 Takeda, Kofu, Yamanashi, Japan

2 Nano Ceramics Center, National Institute for Materials Science, Tsukuba, Ibaraki, Japan *Corresponding Author: swada@yamanashi.ac.jp

Nowadays, Lead-free piezoelectric materials have been attracting worldwide attention since

the adoption of RoHS/WEEE directives. Generally, BaTiO3 (BT) is well known dielectric and piezoelectric material with a piezoelectric coefficient of 190 pC/N.[1] In 2007, two groups reported big breakthrough in electrical properties for BT ceramics. One of the groups reported superior properties for fine-grained while the other for [110]-oriented BT ceramics.[2, 3] However, BaTiO3 ceramics are difficult to use in real applications because of its low Curie temperature.

So, we have focused on (Bi0.5Na0.5)TiO3–BaTiO3 (BNT-BT) ceramics which are well-known candidate for lead-free piezoelectric materials because of their high Curie temperature. Curie temperature of 85BNT-15BT composition has reported to be more than 200 oC without depolarization temperature (Td).[4]

Fig 1. Principle for magnetic alignment of diamagnetic particles[5]

To achieve high performance BNT-BT ceramics, we aim to prepare fine-grained and [111]-

textured ceramics. However, Template Grain Growth (TGG) method is difficult to prepare fine-grained and orientation in a specific direction due to its characteristics. So, we investigated colloid method to prepare textured ceramics in high magnetic field, as shown fig. 1. Moreover, [111] orientation in BNT-BT system was achieved by using hexagonal BT powder.

In this work, we tried to make BNT-BT ceramics with hexagonal BT powders without magnetic field. To make BNT-BT ceramics with colloid method, various variables, such as kind of suspensions and ratio of hexagonal BT powders had to be optimized. Finally, we evaluated various properties of BNT-BT ceramics prepared by colloid method.

References [1] Jaffe et al., Piezoelectric Ceramics (1971) [2] T. Karaki et al., Jpn. J. Appl. Phys., 46, 4, L97-L98 (2007) [3] S. Wada et al., Jpn. J. Appl. Phys., 46, 10B, 7039-7043 (2007) [4] T. Takenaka et al., Jpn. J. Appl. Phys., 30, 9B, 2236-2239 (1991) [5] T. S. Suzuki and Y. Sakka, Scripta Mater., 52, 7, 583-586 (2005)

Review of ferroelectric and magnetic soft modes in multiferroics Stanislav Kamba* and Filip Kadlec

Institute of Physic, Czech Academy of Sciences, Na Slovance 2, Prague 8, Czech Republic *Corresponding author: kamba@fzu.cz

In proper ferroelectrics, the large dielectric anomaly in permittivity H’(T) occurring at the

Curie temperature TC is caused by softening of a polar optical phonon or by slowing down of a microwave dielectric relaxation. Such soft modes drive ferroelectric phase transitions in the type-I multiferroics like BiFeO3, PbFe0.5Nb0.5O3 or strained EuTiO3. In the spin-order induced ferroelectrics (i.e. type-II multiferroelectrics), only small dielectric anomalies are observed at ferroelectric TC, because these materials belong to improper or pseudoproper ferroelectrics (i.e., the order parameter is some other quantity than polarization). For the type-II multiferroics with noncollinear magnetic structure, Katsura, Balatsky and Nagaosa predicted already in 2007 that soft spin waves hybridized with the electric polarization should drive the ferroelectric phase transitions.[1] These spin waves can be called electromagnons, because they contribute to both dielectric permittivity and magnetic permeability. Only last year, Niermann et al.[2] confirmed this prediction, having discovered a critical slowing down of a Drude-like dielectric relaxation near the multiferroic phase transition in MnWO4. The relaxation was observed in the microwave dielectric spectra only within 0.2 K above TC, because at higher temperatures the relaxation frequency hardens above 10 GHz and its dielectric strength becomes negligible. This excitation was interpreted as the soft electromagnon which drives the ferroelectric phase transition.2

Similar small and narrow dielectric peaks at TC are known from most spin-induced ferroelectrics, but they were never investigated using microwave dielectric spectroscopy in the vicinity of TC. Nevertheless, electromagnons were observed for most multiferroics with spiral magnetic structures in their THz spectra. Thus, their frequencies are two or three orders of magnitude higher and we propose, based on analogy with phonons in structurally modulated crystals,[3] that they correspond to the amplitudon component of the spin wave, whereas the soft microwave component is a phason component of the electromagnon activated by the inverse Dzyaloshinskii-Moriya interaction. The frequencies of THz electromagnons harden upon cooling below TC and their dielectric strengths increase due to the spin-phonon coupling, therefore they are responsible for the corresponding increases in permittivity. We will demonstrate this behaviour in TbMnO3 and BiFeO3 [4] perovskites as well as in (BaxSr1-x)3Co2Fe24O41 [5] crystallizing in the Z-type hexaferrite structure. In the last case, we will also discuss the magnetic-field dependence of the magnon and electromagnon spectra.

Another type of multiferroics with improper ferroelectric phase transitions is represented by orbital-order driven ferroelectrics with the Jahn-Teller transitions. GaV4S8 belong to this family and it undergoes the ferroelectric and magnetic phase transitions at 44 K and 12.7 K. In its paraelectric phase, an overdamped soft mode arising from coupled orbital and polar fluctuations was detected in the THz region and its relaxation frequency drops by five orders of magnitude at the first order ferroelectric phase transition.[6] Another small hardening was detected at the magnetic phase transition, when Skyrmion lattice appears.[6] References [1] H. Katsura, A.V. Balatsky, and N. Nagaosa, Phys. Rev. Lett. 98, 027203 (2007). [2] D. Niermann et al., Phys. Rev. Lett. 114, 037204 (2015). [3] J. Petzelt, Phase Transitions 2, 155 (1981). [4] S. Skiadopoulou et al., Phys. Rev. B 91, 174108 (2015). [5] F. Kadlec et al., submitted to Phys. Rev. B, [6] Zhe Wang et al., Phys. Rev. Lett. 115, 207601 (2015).

Positive and negative electrocaloric effect in the presence of defect dipolesY.-B. Ma,1,* A. Grünebohm,2 K.-C. Meyer,1 C. Kalcher,1 K. Albe,1 and B.-X Xu1

1Institute of Materials Science, Technische Universität Darmstadt, Germany2Faculty of Physics and and CENIDE, University of Duisburg-Essen, Germany

*Corresponding Author: y.ma@mfm.tu-darmstadt.de

The influence of defect dipoles on the electrocaloric effect (ECE) is investigated by meansof lattice-based Monte-Carlo simulations [1,2], utilizing a Ginzburg-Landau type effectiveHamiltonian. Fixed dipoles are introduced to describe oxygen vacancy-acceptor associates,which can be parallel or anti-parallel to the external field. The combination of canonical andmicrocanoncial simulations provides a direct way to evaluate the ECE. Our results show that inthe presence of anti-parallel defect dipoles the sign of the ECE varies from positive to negativewhen increasing the density of defect dipoles (see Fig.1(a)). Moreover, a transition from thenegative to positive ECE can be observed at a given density of anti-parallel dipoles when theexternal field increases (see Fig.1(b)). These transitions can be interpreted by the delicateinterplay between the internal and external fields, and are explained by the domain structureevolution and related field-induced entropy changes. The results are compared to those obtainedby simple Ising model and MD simulations [1,3] employing an ab initio based effectiveHamiltonian. All three scenarios show a good qualitative agreement. Furthermore, we suggest anovel electrocaloric cycle with higher cooling effect, by making use of the negative ECE in thepresence of defect dipoles.

Figure 1. Influnce of the density of the anti-parallel defects (a) and the strength of the external field (b) on the electrocaloric effect

References[1] Y.-B. Ma et al., arXiv: 1507.05004 (2016)[2] Y.-B. Ma, K. Albe, B.-X. Xu, Phys. Rev. B, 91, 184108 (2015)[3] A. Grünebohm, T. Nishimatsu, Phys. Rev. B, in press (2016)

Dielectric properties and relaxation behavior in Mn-doped Ca0.6Sr0.4TiO3 ceramics for energy storage

L. Zhang, J. Xie, Q. Xu, M. H. Cao, H. Hao, Z. H. Yao and H. X. Liu* State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, No.122 Luoshi Road, Hongshan District, Wuhan, People’s Republic

of China *Corresponding Author: lhxhp@whut.edu.cn

Linear dielectric materials are ideal options for energy storage application due to the typical

high energy storage efficiency and breakdown strength. In the present work, pore free Ca0.6Sr0.4TiO3 (CST) ceramics with various amount of Mn dopants (0%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 1.0%, 1.5%, 2.0%) were prepared via solid state reaction method. P-E curves were measured under a temperature range of 25~175oC. Energy storage densities and efficiencies were calculated and found to be greatly enhanced for CST with moderate Mn dopants, to be specific, 0.5% Mn demonstrated the optimized high temperature energy storage properties. The conduction relaxation behavior was investigated and the conduction activation energy was found to be sensitive to the variation of energy storage properties. Additionally, vacancy related defect dipole was analyzed by dielectric loss-frequency spectrum in this work, for further explanation of the enhanced high temperature energy storage properties.

References [1] H. Lee et al., Journal of the American Ceramic Society, 96, 1209-1213 (2013) [2] R. Merkle, J. Maier, Physical Chemistry Chemical Physics, 5, 2297-2303 (2003) [3] M. Dawber, J. F. Scott, A. J. Hartmann, Journal of the European Ceramic Society, 21, 1633-1636 (2001)

Over-poling Study of PMN-PT and PIN-PMN-PT Crystal Grown by Vertical Gradient Freeze Method

Zibo Jiang1 1Innovia Materials (Shanghai) Co., Ltd

*Corresponding Author: jiang@innoviamaterials.com Lead magnesium niobate – lead titanate (PMN-PT) crystal was grown by Vertical Gradient

Freeze (VGF) method. Poling reactions of PMN-28%PT and PMN-32%PT were studied. Different poling voltages were used to pole along [001] direction, the resultant impedance, dielectric constant, electromechanical coupling coefficient and dielectric loss were recorded. It is evident that poling of PMN-28%PT saturates at around 320 kV/mm and poling of PMN-32%PT saturates at around 200 kV/mm. As poling voltage increases, over-poling starts to manifest at around 1400 V/mm for PMN-28%PT (Figure 1) and 1000 V/mm for PMN-30%PT. Previous works attributed over-poling to field-induced phase change from rhombohedra to monoclinic or tetragonal phase, which is to be confirmed by observing permittivity in zero-field heating environment.

Several methods were deployed in attempt to recover over-poling damages, including heating the crystals above Curie temperature and reverse poling. However, such attempts failed to recover key properties such as impedance (Figure 1). It is therefore concluded that the over-poling of PMN-PT may be irreversible in transducer engineering practices and should be carefully avoided.

Similar study is to be extended to the tertiary crystal system PIN-PMN-PT.

Figure 1. Plot of impedance vs. frequency after poling at different voltages for (001) PMN-

28%PT plates, demonstrating the crystal is over-poled at 1400 V/mm along [001], and that such damage cannot be recovered by heating the crystal above Curie temperature.

References [1] A. A. Bokov and Z.-G. Ye, Physics Review B 66, 094112 (2002). [2] Z. Jiang, 2015 Joint IEEE International Symposium on the Applications of Ferroelectric, International Symposium on Integrated Functionalities and Piezoelectric Force Microscopy Workshop (ISAF/ISIF/PFM), Singapore, 56-59 (2015). [3] Y. Lu et al., Applied Physics Letters 78, 3109 (2001). [4] Y. Lu et al., Applied Physics Letters 80, 1918 (2002). [5] K.K. Rajan et al., Sensors and Actuators A 133 (2007) 110–116. [6] M. Shanthi et al., Applied Physics Letters 86, 262908 (2005). [7] C.-S. Tu et al., Physics Review B 70, 220103 (2004).

Depolarization Behavior and Space Charge Distribution in Polar and Nonpolar Ceramic-polymer Composite Dielectrics

Zhenxing Yue*, Li Zhang, Yunzhou Shi, Jie Zhang, Longtu Li State Key Laboratory of New Ceramics and Fine Processing, School of Materials Science and

Engineering, Tsinghua University, Beijing 100084, China *Corresponding Author: yuezhx@tsinghua.edu.cn

The defect response and interfacial effect are especially of significance for dielectric loss

and electric breakdown in ceramic-polymer composite dielectrics for microwave and energy-storage applications. The characterization of defect response in composite dielectrics has been a technical challenge. In this work, depolarization behavior and space charge distribution which are associated with the defects and charge response in ceramic-polymer micro- and nano-composites in nonpolar Ba6-3xNd8+2xTi18O54-HDPE and polar BaTiO3-PVDF dielectric systems were studied through thermally stimulated depolarization current (TSDC) and the pulsed electro-acoustic (PEA) techniques. TSDC spectroscopy revealed that the defect charges are mainly trapped at ceramic/polymer interface in the composite dielectrics, while in pure polymers of HDPE and PVDF they are located at the interface between crystalline and amorphous regions, and the depolarization current is determined by the concentration of interface. The PEA analysis indicated that the space charges are mainly situated in the interface between the medium and the electrode under an external electric field. Moreover, ceramic particles can effectively inhibit the space charge injection into inner dielectrics, which is beneficial to dielectric withstanding behavior. This work demonstrated that the TSDC and TEA data are helpful for understanding the charge-related dielectric mechanism, such as dielectric loss and electric breakdown, in ceramic-polymer composite dielectrics.

Fig.1 TSDC spectra of BNT-HDPE composite dielectrics

Fig.2 Space charge distribution in BaTiO3-PVDF nanocomposite dielectrics

Broken symmetry in paraelectric phase and polar nano regions Sina Hashemizadeh and Dragan Damjanovic

Ceramics Laboratory, Swiss Federal Institute of Technology in Lausanne–EPFL, 1015 Lausanne, Switzerland

Corresponding Author: sina.hashemizadeh@epfl.ch

Perovskite ferroelectrics are non-centrosymmetric and polar below Curie Temperature (TC) and experience a temperature-driven phase transition at TC to a paraelectric phase, where polarization is lost. The paraelectric phase of the most ferroelectrics is centrosymmetric (often cubic) and therefore non-piezoelectric. However, even in a centrosymmetric paraelectric phase, ferroelectrics exhibit interesting types of electro-mechanical and electro-thermal coupling which are forbidden by centric symmetry. Our objective is to study the origins of symmetry breaking in paraelectric phase of ferroelectrics which could be related to presences of polar nano regions (considered as nucleus of ferroelectric phase) and/or charged point defects, aligned by strain gradient in the material.

It is known that polar nano regions in relaxor ferroelectric materials contribute to dielectric nonlinearity and show dynamics similar to that observed by domain walls in ferroelectrics. The dielectric nonlinearity may thus be used as an indirect evidence of presence of polar regions in the paraelectric phase of a ferroelectric. Recently we have shown that nonlinearity could be used to infer presence or absence of polar precursors in hexagonal and cubic polymorphs of BaTiO3 [1]. In this study, different compositions of BaXSr1-XTiO3 (BST) solid solution (0≤x≤0.6) are prepared in form of ceramics and used to investigate dielectric nonlinearity above TC. All of selected compositions are paraelectric at room temperature with TC changing from -208 °C to -1 °C. The amplitude and phase angle of first three harmonics of the dielectric nonlinearity were characterized. Harmonic analysis of an ac signal uses the discrete Fourier transform and permits the separate study of various contributions to nonlinearity. In BST system in paraelectric phase dielectric nonlinearity could be due to motion of polar regions (either residual ferroelectric domains as suggested in [2] or polar nano regions, as in relaxor ferroelectrics) and/or defects. In the former case it is proposed that, dynamics of domain walls could be described by Rayleigh law [2]. As shown in figure 1 for Ba0.6Sr0.4TiO3 (BST 60-40) ceramics, our results suggest that nonlinearity of dielectric permittivity cannot be explained by Rayleigh law, characteristic for motion of domain walls, because the third harmonic is in phase with the first one, while out of phase relationship is expected in Rayleigh-like case. The dielectric nonlinearity is rather similar to that reported for lead-based relaxors. More investigation is underway to identify possible effects of charged defects on dielectric nonlinearity.

(a) (b)

Figure1. Field dependence of (a) the first and the third harmonic of dielectric permittivity and (b) the phase angle of first three harmonics for BST 60-40. The decrease of the first harmonic with increasing field is due to the lattice contribution.

!References [1] S. Hashemizadeh, A. Biancoli, and D. Damjanovic, Journal of applied physics 119, 094105 (2016). [2] Garten, Lauren M., et al. Journal of the American Ceramic Society1-6(2016).

Heat exchange in pyroelectric energy harvesting devices P. V. Yudin,1,2,* M. Hrebtov,1,2 and E. Maheux3

1Kutateladze Institute of Thermophysics, Siberian Branch of Russian Academy of Sciences, Lavrent’eva Av. 1, Novosibirsk, Russia

2Novosibirsk State University, Pirogova St. 2, Novosibirsk, Russia 3Ecole polytechnique, Route de Saclay, Palaiseau, France

*Corresponding Author: petrlausanne@mail.ru

Nowadays much attention is paid worldwide to the development of effective and

environmentally friendly energy conversion technologies. Of particular importance is the problem of conversion of waste heat into usable electricity. Pyroelectric effect is a worthy alternative to conventionally used Seebeck effect for thermoelectric conversion. Being light-weight, pyroelectric lamellar devices are promising for autonomous applications e.g. for charging a car battery from the heat of the exhaust pipeline. While Seebeck effect utilizes temperature gradient, pyroelectric energy harvesting implies cyclical change of temperature [1]. The higher is the frequency of the thermodynamic cycles – the more electric power will be produced by the pyroelectric device. Organization of effective heat exchange between the pyroelectric material and the cooling/heating medium is a central task for efficient energy harvesting.

Figure 1. Lamellar pyroelectric generator in a flow with alternating temperature. Temperature is shown with color/brightness.

In the present work we theoretically address the problem of active cooling/heating of a

lamellar pyroelectric generator by a flow of gas or liquid. Among the geometries of the system we consider one where a fluid with alternating (stepwise) temperature enters a channel containing pyroelectric lamella. Distribution of temperature for this geometry, shown in fig. 1, was obtained by numerical simulation of unsteady fluid-solid conjugate heat transfer problem. For the analysis of the heat flux we also use empirical relationships known for boundary layer adjacent to the surface of the lamella. Optimization of the parameters was done to maximize expected power of pyroelectric generation. Dependencies on the thickness of the lamella, the frequency of the thermodynamic cycles, and the parameters of the fluid will be discussed.

References [1] G. Sebald, E. Lefeuvre, and D. Guyomar. IEEE transactions on ultrasonics, ferroelectrics, and frequency control, vol. 55, no. 3, pp. 538-551 (2008)

pyroelectric lamella flow

boundary layer hot fluid

cold fluid

Polarization dynamics variation across the temperature- and composition-driven phase transitions in lead-free BZT-xBCT ferroelectrics

S. Zhukov,1 M. Acosta,1 Y. A. Genenko1*, and H. von Seggern1 1Institut für Materialwissenschaft, Technische Universität Darmstadt, Alarich-Weiss-Straße 2,

64287 Darmstadt, Germany *Corresponding Author: genenko@mm.tu-darmstadt.de

Lead-free BZT-xBCT ferroelectrics [1] have been considered recently as a potential replacement for widely used but potentially toxic PZT piezoceramics. In this work, the method of thermally stimulated depolarization currents (TSDC) and polarization switching experiments over a large field, time and temperature regimes were employed to refine the controversial phase diagram of BZT-xBCT ceramics and comprehend its relation to ferroelectric and piezoelectric properties. Three ferroelectric phases for the composition range of 0.30≤x≤0.60 were detected, which were assigned to the rhombohedral (R), orthorhombic (O) and tetragonal (T) symmetries. Besides, it was noticed that the rhombohedral phase reveals much lower polarization thermal stability than the tetragonal one. Consequently the evolution of the dynamic polarization response was traced down in both cases of the composition-driven and temperature-driven crossing the R-O and O-T phase boundaries. Analysis of the polarization dynamic responses was performed by applying the Inhomogeneous Field Mechanism model (IFM) [2] which allowed insight in the evolution of microscopic switching parameters [3,4]. It was established that the spontaneous polarization shows maximum not just at R-O or O-T boundaries, as might be expected from the previous observations, but over the entire intermediate phase region where the activation barrier for polarization switching appears to be small.

References [1] W. Liu and X. Ren, Phys. Rev. Lett. 103, 257602 (2009) [2] Y.A. Genenko, S. Zhukov, S.V. Yampolskii, J. Schütrumpf, R. Dittmer, W. Jo, H. Kungl, M. J. Hoffmann, and H. von Seggern, Adv. Funct. Mater. 22, 2058 (2012) [3] S. Zhukov, Y. A. Genenko, M. Acosta, H. Humburg, W. Jo, J. Rödel, and H. von Seggern, Appl. Phys. Lett. 103, 152904 (2013) [4] S. Zhukov, M. Acosta, Y. A. Genenko, and H. von Seggern, J. Appl. Phys. 118, 134104 (2015)

Upper bounds in electrocaloric cooling G. Suchaneck

Solid State Electronics Lab, TU Dresden, 01062 Dresden, Germany Corresponding Author: gunnar.suchaneck@tu-dresden.de

Electrocaloric (EC) basic research is mainly focused on materials with a first-order phase

transition. This provides a large polarization change in a narrow temperature region near the Curie point. In this case, the upper bound of the EC effect established both experimentally and theoretically is 5 to 10 K.

Recently, we have considered an alternative approach: EC device operation at high electric fields E above the temperature of the maximum dielectric permittivity Tm [1]. Here, the EC response is determined by the temperature coefficient of dielectric permittivity while dielectric losses are comparably low. Also, the condition that the heat rejected to the sink is larger than the heat absorbed from the load is easily fulfilled.

Since the current estimates of the EC upper bound are related to the presence of a phase transition, we have proposed a new upper bound which is based on the fact that only a certain energy density emax might be stored in a dielectric - equivalent to a limit in electrostatic pressure:

2max0

max 12

ETc

TTEC HHHH

�ww

���'

where 'TEC is the EC temperature change, T the temperature, c is the volumetric specific heat, H the relative dielectric permittivity, H0 the vacuum dielectric permittivity, and E the electric field strength. In this case, the maximum entropy change is given by 'Smax = -Hemax/C with C the Curie constant derived from the temperature dependence of H. Our estimation explains the high values of the EC effect previously obtained in relaxor PLZT [2].

A figure of merit of EC materials performance might be derived of considering the coefficient of performance of the refrigeration cycle, the refrigeration capacity and the Fourier number per cycle time [1]:

220

2 1tan dET

TTcFoM EC

���

���'�

GHHNG

with GT the full width at half maximum of the entropy versus temperature curve, N the thermal conductivity, tanG the dielectric loss tangent, and d the thickness of the EC material. With regard to our upper bound of the electrocaloric effect, relaxor ferroelectrics are the best choice for EC application.

EC relaxor materials is characterized by different time scales, two electronic ones due to (i) polarization response and (ii) polar nanoregion dynamics and two thermal ones, (i) the thermal transit time during which the sample reaches internal thermal equilibrium (called by us the acoustic limit) and (ii) the time constant of the material´s volume during which thermal equilibrium with the environment is established. The rise time of the electrical field applied during the adiabatic depolarization (cooling) step should not exceed the acoustic limit. On the other hand, the performance of EC cooling elements is limited by the thermal time constants of heat switches or by the heat transfer coefficient to the gaseous or liquid heat transfer agent of active EC regenerators.

Thus, cooling power densities of a few W/cm2 and temperature spans in the order of a 20 K (in regeneration systems) are gainable at a cycle time of 100 ms using lead-free relaxor EC elements.

References [1] G. Suchaneck, G. Gerlach, Materials Today: Proceedings 3, 622-631 (2016) [2] S.G. Lu et al., Appl. Phys. Lett. 97, 162904 (2010)

Evaluation of shear-mode piezoelectric response in PZT ceramics by high energy synchrotron XRD

D.A. Hall1,*, L. Daniel2, M. Watson3, A. Condie3, T.P. Comyn4, A.K. Kleppe5 and P.J. Withers1

1 School of Materials, University of Manchester, Manchester M1 7HS, UK 2 LGEP (CNRS UMR8507, SUPELEC, UPMC, Univ Paris-Sud), 91192 Gif sur Yvette cedex - France 3 Xaar, 316 Cambridge Science Park Milton Rd, Cambridge CB4 0XR, UK 4Ionix, 3M Buckley Innovation Centre, Firth Street, Huddersfield HD1 3BD 5 Diamond Light Source Ltd, Diamond House, Harwell Science and Innovation Campus, Didcot,

Oxfordshire OX11 0DE, UK *Corresponding Author: David.A.Hall@manchester.ac.uk

The longitudinal and transverse piezoelectric responses of lead zirconate titanate (PZT) ceramics are used widely in applications such as stack actuators and bimorphs respectively. In contrast, shear-mode actuators are less common but provide significant advantages in some areas of nanopositioning and high frequency inkjet printheads.

The purpose of the present study was to investigate the mechanisms contributing to the shear-mode piezoelectric behavior in a commercial PZT ceramic. This was achieved by the application of a bipolar electric field in a direction perpendicular to that of the stable remanent polarization; simultaneously, high energy x-ray diffraction (XRD) patterns were recorded in transmission using the I15:Extreme Conditions beamline at the Diamond light source, as illustrated in Figure 1(a). The components of lattice strain and ferroelectric domain fractions were obtained by analysis of the diffraction peak profiles, carried out over a range of azimuthal angles, ψ, relative to the direction of the applied electric field.

It is shown that the largest lattice strains were obtained initially, at low electric field levels, along the directions for which ψ = ± 45° and ± 135°, consistent with the shear-mode piezoelectric effect. At higher electric field levels, exceeding the ferroelectric coercive field, the shear strain was reduced while the longitudinal and transverse strains increased due to re-polarisation along the direction of the applied field. Rotation of the average polarization direction towards that of the applied electric field was determined in terms of the principle strain direction, ψp, as shown in Figure 1(b).

(a) (b)

Figure 1. (a) Schematic view of experimental set up for in-situ diffraction experiments and (b) variation in orientation of principle strain as a function of increasing electric field.

Bismuth sodium titanate based lead-free piezoelectric ceramic coatings fabricated by thermal spray

Kun Guo,1,2 Shuting Chen,1 Chee Kiang Ivan Tan,1 Kui Yao,1,* and Francis Eng Hock Tay2 1Institute of Materials Research and Engineering, A*STAR (Agency for Science, Technology

and Research), 2 Fusionopolis Way, Innovis, Singapore 138634 2Department of Mechanical Engineering, National University of Singapore, 9 Engineering Drive

1 Singapore 117575 *E-mail: k-yao@imre.a-star.edu.sg

Currently, people aspire to achieve lead-free piezoelectric ceramics with excellent

properties to replace the lead-based ceramics, because of the environmental concern of lead hazard aggravated by the expanded applications of piezoelectric ceramics in sensors, transducers, actuators, and energy harvesters. Scalable ceramic deposition processing is desired to produce lead-free piezoelectric coatings at low cost over a large area, in addition to the existing methods established for fabricating piezoelectric layers including screen printing, tape casting, and physical vapor deposition. With high productivity, large area coating ability, and less limitation of substrates, thermal spray process has widely been used for producing thermal barrier and other protective coatings in aerospace and oil and gas industry for many years. However, thermal spray method has not been successfully applied for producing either lead-based or lead-free piezoelectric ceramic coatings with high performance properties.

Among lead-free piezoelectric materials, bismuth sodium titanate (BNT)-based piezoelectric ceramics has attracted interest due to their high remnant polarization and strong electromechanical coupling effect. In this work, BNT-based lead-free piezoelectric ceramic coatings were prepared by thermal spray process. During the thermal spray process, the powder was heated to molten or semi-molten state and then quenched and solidified on the substrates. Retaining the stoichiometric composition and keeping certain ionic bonding structure at the high temperature during thermal spray process is important to realize the aimed structure and properties. We systematically investigated the characteristics of two compositions: Bi0.5Na0.5TiO3 (BNT) and Bi0.5(Na0.70K0.20Li0.10)0.5TiO3 (BNKLT), and further evaluated their applicability for thermal spray process. The ceramic powder and thermal sprayed ceramic coatings were evaluated by various thermal and x-ray analysis techniques. The morphology and electrical properties including dielectric, ferroelectric and piezoelectric of the obtained coatings were examined. The effects of the melt behavior of the compositions on crystal growth and structure in the resulting thermal sprayed coatings were discussed.

Optical refraction tuned by substrate in epitaxial (K,Na)NbO3 films

E. Chernova1,2, A. Dejneka*1, T. Kocourek1, M. Jelinek1, M. Tyunina3,1 1Institute of Physics, CAS, Na Slovance 2, Prague 8, Czech Republic, 18221

2 Czech Technical University, Technická 2, Prague 6, Czech Republic, 166 27 3 Microelectronics Research Unit, Faculty of Information Technology and Electrical

Engineering, University of Oulu, P. O. Box 4500, FI-90014 Finland

*Corresponding Author: dejneka@fzu.cz

Thin single-crystal epitaxial films of perovskite-structure oxide ferroelectrics can enable advanced integrated optical devices. However, compared to crystals, optical properties of such films can change due to effects of epitaxy on crystal symmetry and lattice strain therein. Here, we report on refractive index experimentally obtained in epitaxial K0.5Na0.5NbO3 films grown on different substrates: SrTiO3(001) and DyScO3(011). The optical properties of the films were explored by variable angle spectroscopic ellipsometry (VASE) with J. A. Woollam ellipsometer working in the VIS-UV 0.74-9 eV spectral range. The obtained ellipsometric spectra were analyzed using the WVASE32 software package. The index of refraction differs by approximately Δn = 0.5 in the transparency range of the films: it is clearly larger in the film on DyScO3 as shown in Fig. 1.

Figure 1. Refractive index n in the K0.5Na0.5NbO3 films

Although the physical mechanisms responsible for the demonstrated effect require further

studies, the phenomenon is promising for creating dedicated thin films for optoelectronic and photonic applications.

Acknowledgements This work was supported by the Czech Science Foundation (Grant No. 15-13778S )

A change of climate: using temperature, relative humidity, and electrostatic boundary conditions to control ferroelectric domain switching and geometry

P. ParuchDepartment of Quantum Matter Physics, University of Geneva, 24 Quai Ernest-Ansermet,

Geneva, Switzerland *Corresponding Author: patrycja.paruch@unige.ch

In ferroelectric materials, the structure and stability of domains with different polarisation depends crucially on both external boundary conditions and internal defects which together determine the screening of depolarising fields, nucleation thresholds, and domain wall pinning. Here, we explore their combined effects on polarisation orientation, switching dynamics, domain wall roughness, and domain wall conduction, using scanned probe microscopy and structural characterisation of epitaxial ferroelectric thin films, and focusing in particular on the role of surface water, temperature, and electrostatic screening.

In PbTiO3 we show a reversal of the intrinsic polarisation orientation and imprint as a function of growth temperature, under varying electrostatic screening, and relate the observed effects to oxygen vacancy gradients [1]. In Pb(Zr0.2Ti0.8)O3 thin films, we map in detail the effects of relative humidity and temperature on switching dynamics, and investigate the earliest stages of domain switching using a “pump-probe” approach [2]. In the same samples, we also highlight their key role of surface adsorbates and oxygen vacancies in determining the conductive vs. insulating electrical transport properties at the domain walls [3]. Finally, using a novel nebuliser-based design of low-noise, precision humidity controller [4], we explore the two-way nature of the interactions between the ferroelectric films and surface water, mapping out the variations in water adsorption as a function of polarisation orientation.

References [1] C. Lichtensteiger et al, accepted N. J. Phys (2016)[2] C. Blaser and P. Paruch, New J. Phys. 17, 013002 (2015)[3] I. Gaponenko et al, Appl. Phys. Lett. 106, 162902 (2015)[4] I. Gaponenko et al, manuscript submitted

Stress Control on Sol-Gel PZT Preparation for Highly Sensitive Diaphragm Structures of Ultrasonic Microsensors

K. Yamashita*, J. Shiomi, T. Nishiumi, and M. Noda Graduate School of Science and Technology, Kyoto Institute of Technology,

Matsugasaki, Kyoto, Japan *Corresponding Author: yamashita.kaoru@kit.ac.jp

Piezoelectric ultrasonic microsensors were fabricated with sol-gel derived lead-zirconate-

titanate (PZT) capacitors on thermally oxidized silicon (SiO2) diaphragms. Residual stress of the SiO2 causes buckling on the diaphragms and upward-buckled diaphragms realize higher sensitiv-ity than flat or downward-buckled ones [1]. Since the sol-gel PZT with tensile stress allows the diaphragms to buckle upward [2] but reduces the buckling deflection [3], the residual stress of the PZT should be carefully controlled. Previously the authors reported that pyrolysis tempera-ture in the sol-gel process changed the buckling deflection of the diaphragms [4]. However, too strong tensile stress flattened the diaphragms and the residual stress could not be obtained from them. In this work, we evaluated the PZT stress on the wafers under the preparation conditions in varied pyrolysis temperatures and modified deposition procedures.

Thermally oxidized 2-inch silicon wafer was used as the substrate and bottom electrode of Pt/Ti films were deposited by using rf sputtering. Sol-gel so-lution of PZT (Mitsubishi Materials, E1, 15%wt, 115/52/48) was spin-coated on the bottom electrode and pyrolyzed on a hot plate to form a gel film at 250, 300, 350 or 400°C. After some sets of the spin-coating and pyrolysis, the gel film was crystallized by annealing in O2 at 650°C for 10 minutes. The set was repeated totally 15 times to the film thickness 950 nm. Two types of annealing procedure were carried out; Process A: annealed after 5th, 10th and 15th pyrolysis; Process B: annealed after 1st, 5th, 10th and 15th pyrolysis. The films were evaluated in their crystalline structure by using X-ray diffractometry (Bruker, D8 Discover) and curvature of the wafer by using a stylus profiler (Bruker, Dektak XT).

Figure 1 shows XRD patterns of the PZT films. Process A and B successfully yielded (111)- and (100)-oriented PZT films, respectively, except the 400°C-pyrolysis case. Figure 2 shows in-plane tensile force and stress. Stoney formula [5] was used to evaluate the in-plane force of the outermost sur-face film from the curvature of the wafer. The in-plane force of the PZT was calculated by subtracting the contribution of the Pt from the force after the PZT preparation. Note that the Pt film changed its stress to tensile after PZT annealing, and the Pt contribution was obtained from annealed Pt film. The residual stress decreases with raising the pyrolysis tempera-ture as shown in Fig. 2, which had been partly unclear in the previous results on the diaphragms. The (100)-oriented PZT films have smaller stress than (111)-oriented ones. Crystalline structure relaxed in 400°C-pyrolysis and it allowed the PZT films to reduce their stress, which means that it is suitable for the diaphragm buckling for the highly sensitive structures. References [1] K. Yamashita, et al., Sens. Actuat. A, vol. 139, 118–123 (2007). [2] K. Yamashita, et al., Proc. IEEE Sensors 2014, 106–109 (2014). [3] K. Yamashita, et al., Sens. Actuat. A, vol. 165, 54–58 (2011). [4] K. Yamashita, et al., Proc. ISAF 2015, 44–47 (2015). [5] R. W. Hoffman, Physics of Thin Films, vol. 3, 211–273 (1966).

!

!Figure 1. XRD patterns of the PZT films through (a) Process A and (b) Process B.

Figure 2. Residual stress of the PZT films versus pyrolysis temperature.

Rethinking Ceramic Processing as a Means to Develop Sustainable Manufacturing Practices for Ferroelectric and Dielectric Materials

Clive A. Randall,* Hanzheng Guo, Jing Guo, and Amanda Baker Materials Research Institute, The Pennsylvania State University, Millennium Science Complex,

University Park, PA 16802, USA *Corresponding Author: car4@psu.edu

Ceramic processing is a costly and highly energetic process. In considering the world’s future

emission restrictions, following the international agreements of COP21, material scientists need to consider alternative, low energy processing routes that can be readily scaled into large scale manufacturing of electroceramic devices, such as multilayer ceramic capacitors and piezoactuators. During this talk, we will discuss a number of routes that substantially reduce the energy budget for processing of important materials. We will contrast dielectric and piezoelectric properties of these materials relative to the more traditional solid state thermal processing.

Graphene field-effect transistors on LiNbO3 ferroelectric substrates A. Vorobiev,1,* S. Bidmeshkipour,2 M. A. Andersson1, A. Kompany2 and J. Stake1

1Department of Microtechnology and Nanoscience, Chalmers University of Technology, SE-41296 Gothenburg, Sweden

2Department of Physics, Ferdowsi University of Mashhad, 9177948974, Mashhad, Iran *Corresponding Author: andrei.vorobiev@chalmers.se

The property of very high carrier mobility and velocity in graphene enables the possibility of

much faster electronics than with traditional semiconductors. However, the channel mobility in graphene field-effect transistors (G-FETs) is usually strongly degraded by Coulomb scattering caused by charged impurities. Additional issue is the zero-bandgap in monolayer graphene, which limits the high frequency power gain of the G-FETs. The both issues can be effectively addressed by using ferroelectric as a G-FET substrate. The field of the ferroelectric polarization screens the charged impurity field [1] and, also, can be used for bandgap engineering in the bilayer G-FETs [2]. In this paper, we report the effect of LiNbO3 ferroelectric substrate on the carrier mobility in top gated monolayer graphene field-effect transistors (G-FETs). We show that, at the same residual concentration of the charge carriers, the mobility in G-FETs on LiNbO3 substrate is higher than that on the SiO2/Si substrate (Fig. 1). The effect is associated with reduction of Coulomb scattering via screening the charged impurity field by the field induced in the ferroelectric substrate [2], but significant only for mobilities below 1000 cm2/Vs. Raman spectra analysis [3] and correlations established between mobility and microwave loss tangent [4] of the Al2O3 gate dielectric indicate that the charged impurities are located predominantly in the gate dielectric and/or at the gate dielectric/graphene interface and likely associated with oxygen vacancies. The gate dielectric technology optimization may allow for significant increase in the carrier mobility up to the limitations by other scattering mechanisms. The measured characteristic frequencies of the G-FETs on LiNbO3 substrates are approx. 2 GHz (Fig. 2) and limited mainly by parasitic capacitance at the source/drain electrode side walls. The corresponding intrinsic cutoff frequency for mobility of 300 cm2/Vs is up to 10 GHz.

References [1] S. Adam et al., Proc. Natl. Acad. Sci. USA, 104, 18392-18397 (2007). [2] J. Ding et al., Europhysics Letters, 104, 17009-p1-4 (2013). [3] S. Pisana et al., Nature Materials, 6, 198-201 (2007). [4] A. Vorobiev et.al, J. Appl. Phys. 96, 4642-4648 (2004).

Figure 1. Hole mobility of the G-FETs on SiO2/Si (circles) and LiNbO3 (squares) substrates versus residual concentration of charge carriers (n0). Lines are fitting curves.

Figure 2. Small-signal current gain h21 and unilateral power gain U of the G-FET with gate length of 0.6 µm on LiNbO3 substrate corresponding to the label (14) on Fig. 1.

Strain mechanisms in relaxor ferroelectrics M. Hinterstein,1,* M. Acosta,2 A. Studer,3 and J. Jones4

1Institute for Applied Materials, Karlsruhe Institute of Technology, Haid-und-Neu Strasse 7, 76131 Karlsruhe, Germany

2Material- und Geowissenschaften, Technische universität Darmstadt, Alarich-Weiss-Strasse 2, 64287 Darmstadt, Germany

3Bragg Institute, Australian Nuclear Science and Technology Organization, Locked Bag 2001, 2232 Kirrawee, Australia

4 Department of Materials Science and Engineering, North Carolina State University, 27695 Raleigh, USA

*Corresponding Author: manuel.hinterstein@kit.edu

Considerable efforts have been triggered by environmental concerns to replace lead containing piezoceramics such as Pb(Zr,Ti)O3 (PZT) with environmentally friendly lead-free alternatives. One of the candidate material systems is based on Bi1/2Na1/2TiO3 (BNT). These materials feature a giant strain at off-resonance frequencies and are especially relevant for actuators working in the so called large signal regime [1,2]. There has been a clear progress in the development of BNT-based materials and the scientific understanding behind their electromechanical response, generally attributed to an electric field induced phase transformation [3]. We recently elucidated the significance of field induced phase transformations for maximised strain response in PZT based actuator materials [4–6]. The necessary tools for a detailed analysis of the strain mechanisms consist of models based on the atomic scale and elucidate the interplay of phase transformations, converse piezoelectric effect and domain switching [4]. In this contribution we present a comprehensive analysis of the field induced strain mechanisms in the lead free incipient piezoceramic 0.75BNT-0.25SrTiO3. We demonstrate that, counter to intuition, antiferrodistortive instabilities can also contribute synergetically to the strain output. In fact, we clarify that the joint effect of ferrodistortive and antiferrodistortive structural instabilities can develop a colossal local strain response of (2.4 ± 0.1) %. Depending on the orientations of the individual grains in the polycrystalline material the applied field induces either an antiferrodistortive rhombohedral phase or a ferrodistortive tetragonal phase. With numerical simulations we demonstrate the microstructural processes in relaxor ferroelectrics and compare them with the strain mechanisms in classical PZT based actuator materials. [1] M. Acosta, L. A. Schmitt, C. Cazorla, A. Studer, A. Zintler, J. Glaum, H.-J. Kleebe, W.

Donner, M. Hoffman, J. Rödel, and M. Hinterstein, Sci. Rep. submitted (2016). [2] M. Acosta, L. A. Schmitt, L. Molina-Luna, M. C. Scherrer, M. Brilz, K. G. Webber, M.

Deluca, H.-J. Kleebe, J. Rödel, and W. Donner, J. Am. Ceram. Soc. 98, 3405 (2015). [3] M. Hinterstein, M. Knapp, M. Hölzel, W. Jo, A. Cervellino, H. Ehrenberg, and H. Fuess,

J. Appl. Crystallogr. 43, 1314 (2010). [4] M. Hinterstein, M. Hoelzel, J. Rouquette, J. Haines, J. Glaum, H. Kungl, and M. Hoffman,

Acta Mater. 94, 319 (2015). [5] M. Hinterstein, J. Rouquette, J. Haines, P. Papet, M. Knapp, J. Glaum, and H. Fuess,

Phys. Rev. Lett. 107, 077602 (2011). [6] M. Hinterstein, J. Rouquette, J. Haines, P. Papet, J. Glaum, M. Knapp, J. Eckert, and M.

Hoffman, Phys. Rev. B 90, 094113 (2014).

Structural origin of high piezoelectricity in 0.5Ba(Ti0.8Zr0.2)O3-0.5(Ba0.7Ca0.3)TiO3: the evolution process of morphotropic phase boundary

Chao Zhou,1,* Lixue Zhang,2 and Xiaobing Ren3 1School of Science, Xi’an Jiaotong University, Xianning West Road 28, Xi’an City, China

2School of Materials Science and Engineering, Xi’an Jiaotong University, Xianning West Road 28, Xi’an City, China

3Ferroic Physics Group, National Institute for Materials Science, Tsukuba 305-0047, Japan *Corresponding Author: chao.zhou@mail.xjtu.edu.cn

Global concerns on the environmental pollution and threats to human health by toxic Pb

element inspire the exploration of Pb-free piezoelectric materials. Due to the resolution limit of x-ray diffraction and electron microscope techniques, usually it is difficult to resolve the structural origin of high-performance piezoelectrics i.e. Pb(Zr0.52Ti0.48)O3 and 0.5Ba(Ti0.8Zr0.2)O3-0.5(Ba0.7Ca0.3)TiO3. In this work, from the investigation on dielectric permittivity, piezoelectric coefficient d33, storage modulus and crystal symmetry of (1-x)Ba(Ti0.8Zr0.2)O3-x(Ba1-yCay)TiO3 (BZT-xBCyT) systems, it is revealed that the morphotropic phase boundary (MPB) regime of BZT-xBC0.3T evolves from the orthorhombic phase of BZT-xBC0.0T (Zr-doped BaTiO3). With further theoretical analysis based on a Landau-type model, we show that the high piezoelectricity observed at 0.5Ba(Ti0.8Zr0.2)O3-0.5(Ba0.7Ca0.3)TiO3 is attributed to the low-energy-barrier state caused by the convergence of rhombohedral, orthorhombic and tetragonal phases. Our work not only clarifies the structural origin of high piezoelectricity in 0.5Ba(Ti0.8Zr0.2)O3-0.5(Ba0.7Ca0.3)TiO3, but also provides a new recipe to design MPB-based high-performance ferroelectric functional materials.

Figure 1. Evolution of phase diagram of BZT-xBCyT systems: (a1) BZT-BC0.0T; (a2) BZT-

BC0.1T; (a3) BZT-BC0.2T; (a4) BZT-BC0.3T, and the piezoelectric coefficient d33 of intermediate composition for each system.

References [1] W. Liu and X. Ren, Phys. Rev. Lett., 103, 257602 (2009) [2] Y. Yao, C. Zhou, et al., EPL, 98, 27008 (2012) [3] R. Guo, L. E. Cross, et al., Phys. Rev. Lett., 84, 5423 (2000)

Combined X-ray diffraction measurements of atomic displacements, lattice strain and macroscopic polarization in BaTiO3-based ferroelectric.

S. Gorfman,1,* H. Simons,2 T. Iamsasri3, H. Choe1, J. L. Jones3 1Department of Physics, University of Siegen, Walter-Flex str 3, Siegen, Germany

2 Department of Physics, Technical University of Denmark, Lyngby kgs. 2800, Denmark 3 Department of Materials Science and Engineering, North Carolina State University, Raleigh,

NC, 27695, USA. *Corresponding Author: gorfman@physik.uni-siegen.de

Structure-property relationships in ferroelectrics extend over several length scales,

including positions of atoms in a unit cell, lattice parameters, domain patterns and macroscopic dimension of a device. However, many existing techniques lack the ability to probe different order parameters simultaneously.

The aim of this presentation is to demonstrate the novel efficient experimental technique [1] for the measurements of atomic displacements, lattice strain and macroscopic polarization in ferroelectric ceramics under cyclic electric field. We implemented the stroboscopic data acquisition system, which operates on the principle of a multi-channel analyzer, and provides an ideal platform for the investigation of repetitive processes down to the nanosecond time scale [2].

Figure 1. The result of the combined measurement of three different types of hysteresis loops, showing the field-dependence of atomic positions in the unit cell (left), lattice spacing (middle)

and macroscopic polarization (right) Most significantly, determination of atomic positions is realized using resonant X-ray

scattering, which makes the intensities of Bragg reflections sensitive to structural inversion. Determination of lattice parameters is based on the monitoring of angular position of a Bragg peaks. Finally, X-ray diffraction experiment is combined with the acquisition of the field-polarization hysteresis loop. We demonstrate this approach using a high-energy (30 keV) X-ray beam on a material in which differentiating between multiple polarization reversal mechanisms remains a significant challenge: tetragonal 0.94·BaTiO3-0.06·BiZn0.5Ti0.5O3 (BT-BZT) perovskite-based polycrystalline ferroelectrics.

References [1] S. Gorfman, H. Simons, T. Iamsasri, S. Prasertpalichart, D.P. Cann, H. Choe, U. Pietsch, Y. Watier, J.L. Jones, Scientific Reports, 5, 20829 (2016) [2] S. Gorfman, H. Choe, V.V. Shvartsman, M. Ziolkowski, M. Vogt, J. Strempfer, T. Lukaziewicz, U. Pietsch, J. Dec, Physical Review Letters, 114, 096601 (2015)

Polarization-induced strain and wall roughness in ferroelectric 180° stripedomains probed by diffuse X-ray scattering

A. Boulle,1 I. C. Infante,2,* and N. Lemée3

1Science des Procédés Céramiques et Traitements de Surface (SPCTS), CNRS UMR 7315,Centre Européen de la Céramique, 12 rue Atlantis, 87068 Limoges, France

2Laboratoire Structures, Propriétés et Modélisation des Solides (SPMS), CNRS UMR 8580,CentraleSupélec, Grande voie des vignes, 92295 Châtenay-Malabry, France

3Laboratoire de Physique de la Matière Condensée (LPMC), EA 2081, Université de PicardieJules Verne, 33 rue Saint Leu, 80039 Amiens, France.

*Corresponding Author: ingrid.canero-infante@centralesupelec.fr

Domains are ubiquitous among ferroic materials and are formed during phase transitions asa necessity to reduce the macroscopic manifestations of the order parameter (polarization,magnetization, strain). In the case of ferroelectric thin films, in order to minimize the energy ofthe depolarizing field and in the absence of an efficient charge screening mechanism provided,either by conducting electrodes or surface adsorbates, the arrangement of polarization withinparticular spatial regions, i.e. domains, can be energetically favorable. Among otherconfigurations, periodic 180° stripe domains of alternating up and down polarization can bespontaneously formed. An additional possibility for ferroelectric materials to minimize thedepolarizing field, is to reorient the polarization in directions parallel to surfaces, either by aglobal rotation of the polarization vector, or locally by the formation of polarization vortices.Since the direction of the polarization is restricted by symmetry, the rotation of the polarizationvector gives rise to important ferroelastic strain.

In this work we demonstrate that the nanoscale morphological properties of the domainstructure can be quantitatively determined by diffuse X-ray scattering (DXS) combined withnumerical simulations [1]. The domain size and period, period disorder, domain wall thicknessand roughness as well as the polarization-induced strain can be revealed, even for complexsystems. As a test case, we apply our modeling to tricolor ferroelectric/paraelectric superlattices(SLs) based on PbTiO3 / SrTiO3 / PbZr0.2Ti0.8O3 (PT/STO/PZT) layers. These SLs indeed exhibita well defined 180° stripe domain structure, combined with a global rotation of the polarization,associated with a monoclinic symmetry [2]. We will show from temperature dependentmeasurements that the motion of ferroelectric domain walls appears as a collective process thatdoes not create any disorder in the domain period, whereas the pinning by structural defectsincreases the wall roughness. Additionally, the polarization-induced strain progressivelydecreases with increasing temperature, and vanishes at the Curie temperature.

This work opens the way to in-situ quantitative studies of ferroic domains and domain walldynamics under the application of external stimuli, including electric fields and temperature.

References[1] A. Boulle, I. C. Infante, N. Lemée, J. Appl. Cryst. 49 (2016), in press.[2] N. Lemée, I. C. Infante, C. Hubault, A. Boulle, N. Blanc, N. Boudet, V. Demange, M. G.Karkut, ACS Appl. Mater. Interf. 7, 19906 (2015)

Electrocaloric 0.9Pb(Mg1/3Nb2/3)O3–0.1PbTiO3 multilayer elements for cooling applications

L. Fulanović,1,2,* M. Vrabelj,1,2 S. Drnovšek,1 H. Uršič,1,2 D. Kuščer,1,2 K. Makarovič,1,3

Z. Kutnjak,1,2 V. Bobnar,1,2 and B. Malič1,2

1Jožef Stefan Institute, Jamova cesta 39, Ljubljana, Slovenia 2Jožef Stefan International Postgraduate School, Jamova cesta 39, Ljubljana, Slovenia 3KEKO Equipment, Grajski trg 15, Žužemberk, Slovenia

*Corresponding Author: lovro.fulanovic@ijs.si

Cooling devices based on the electrocaloric (EC) effect are a promising alternative in refrigeration as a substitute for, or as an extension of the conventionally used vapor compression systems. The major obstacle in the progress of EC cooling technologies are insufficiently large EC temperature changes ('T) that can be induced in the EC materials [1]. Lead-based relaxor ferroelectrics, such as 0.9Pb(Mg1/3Nb2/3)O3-0.1PbTiO3 (PMN-PT), exhibit a large 'T due to their large change of polarization with temperature, however at very high electric field amplitudes, i.e. 3.45 oC at 160 kV/cm [2]. Implementing multilayer (ML) ceramic elements allows decreasing the thickness of individual EC elements and thus decreasing the applied voltage while still keeping mechanical stability. However, freestanding ML elements purposely made for the EC application, have not yet been realized.

The aim of this work was to prepare PMN-PT multilayer elements with internal platinum electrodes. The ML elements were fabricated by tape casting the slurry, consisting of the mechanochemically synthesized powder and organic additives, and sintering at 975 °C.

The ML elements with the individual layer thickness of about 60 Pm revealed a dense microstructure, consisting of about 2 Pm grains; and demonstrated low- and high-field dielectric properties comparable to the reference bulk ceramic prepared by dry-compaction of the same powder. The EC effect was measured by indirect and direct methods. The ML elements exhibited the 'T values slightly above 2 K at the applied electric field of 100 kV/cm (V = 600 V) in a broad temperature range from 70 to 105 °C, which was even slightly higher than the 'T values obtained for the bulk material. Such temperature changes would be enough to realize the temperature span of over 12 K in a demo EC cooling device as reported by Plaznik et al.[3].

[1] M. Valant, Prog. Mater. Sci., 57, 980–1009 (2012)

[2] M. Vrabelj et al., Eur. Ceram. Soc., 36, 75–80 (2016)

[3] U. Plaznik et al., Appl. Phys. Lett., 106, 4–8 (2015)

Low-temperature transport phenomena at charged semiconducting domain-walls

P. Schönherr,1* J. Schaab,1 A. Cano,2 M. Fiebig,1 and D. Meier1 1Department of Materials, ETH Zürich, Vladimir-Prelog-Weg 4, 8093 Zürich, Switzerland

2CNRS, Université de Bordeaux, ICMCB, UPR 9048, 33600 Pessac, France *Corresponding Author: peggy.schoenherr@mat.ethz.ch

Ferroic domain walls attracted broad attention as functional nano-objects with unusual

properties, including magnetism, multiferroicity and superconductivity. Particularly interesting are so-called charged ferroelectric domain walls in oxides, where local, diverging electric fields give rise to tunable electronic transport behavior [1]. Despite remarkable progress in experiment and theory, however fundamental aspects concerning the physics of charged ferroelectric domain-walls still fall into largely uncharted territory. Due to the challenging experimental access, this especially applies to the domain-wall ground state, its stability, as well as temperature-driven variations in the electronic transport mechanism and screening of bound domain-wall charges. Thus, low-temperature microscopy studies are highly desirable in order to develop a comprehensive understanding of the domain-wall nano-physics and emergent functionality.

Here, we discuss temperature-dependent variations in the electronic domain-wall transport

in the p-type semiconductor Er1-xCaxMnO3 [2]. By combining low-temperature conducting atomic and electrostatic force microscopy we monitor the (improper) ferroelectric domain pattern and investigate changes in the domain-wall conductance for temperatures between 295 K and 2 K. Our data demonstrate that the domain walls behave like two-dimensional semiconductors adopting their basic properties from the surrounding host material. Additional modulations in the local Schottky barrier, electronic conductance and screening are shown to arise from bound domain-wall charges and the associated diverging electric fields. Our results clarify pending questions about the low-temperature performance and stability of charged domain walls and provide new insight into the general domain-wall physics in semiconducting ferroelectrics. References [1] D. Meier et al., Nature Mater. 11, 284 (2012) [2] J. Schaab et al., Adv. Electron. Mater. 2, 1500195 (2016)

Integrated Hybrid Life Cycle Assessment and Supply Chain Environmental Profile Evaluations of Lead-based PZT versus Lead-free KNN Piezoelectric functional materials

Ibn-Mohammed, T.1, 2*, Koh, S.C.L1, 2, Reaney, I.M.3, Acquaye, A.4, Wang, D.3, Genovese, A.5, Taylor, S.6 1 Centre for Energy, Environment and Sustainability, University of Sheffield, Sheffield, S10 1FL, UK

2Advanced Resource Efficiency Centre, University of Sheffield, Sheffield, S10 1FL, UK 3 Departments of Materials Science and Engineering, University of Sheffield, Sheffield, S1 3JD, UK

4 Kent Business School, University of Kent, Canterbury, CT2 7PE, UK 5 Logistics and Supply Chain Management Research Centre, University of Sheffield, Sheffield, S10 1FL, UK

6 School of Civil and Building Engineering, Loughborough University, Loughborough, LE11 3TU

Abstract

The increasing awareness of the environmental and health threats of lead as well as environmental legislation, both

in the EU and around the world targeted at decreasing the use of hazardous substances in electrical appliances and products

has reinvigorated the race to develop lead-free alternatives to lead zirconate titanate (PZT), which presently dominates the

market for piezoelectric materials. Emphasis has been placed on one of the most likely piezoelectric materials, potassium

sodium niobate (KNN), as a lead-free replacement for PZT. KNN has been speculated to have better environmental

credentials and is considered as a “greener” replacement to PZT. However, a comparative environmental impact assessment

of the life cycle phases of KNN versus PZT piezoelectric materials has not been carried out. Such a life cycle assessment is

crucial before any valid claims of “greenness” or environmental viability of one material over the other can be made and is the

focus of this paper. Against this backdrop, a methodologically robust and environmentally expansive life cycle supply chain

assessment is undertaken within the context of the two piezoelectric materials. Results shows that although the impact of lead

is not negligible, the presence of niobium in KNN constitutes far greater impact across all 16 categories considered. Cost-

benefit analysis of substituting PZT with KNN also indicates that the initial cost of conversion to KNN is greater, especially

for energy usage during production. This environmental assessment has allowed us to define and address environmental health

and safety as well as sustainability issues that are essential for future development. Overall, this work demonstrates an

important application of life cycle assessment and supply chain management to a strategic engineering question which allows

industries and policy makers to make informed decisions regarding the environmental consequences of substitute materials,

designs, fabrication processes and usage.

Demonstration of Spin-Phonon Coupling in IR, THz and MW Spectra of Sr1-xBaxMn1-yTiyO3 Ceramics and Sr1-xBaxMnO3 Thin Films

V. Goian,1,* V. Bovtun,1 C. Kadlec,1 F. Kadlec,1 M. Kempa,1 D. Nuzhnyy,1 B. Dabrowski,2 E. Langenberg,3 J. Pardo3 and S. Kamba1

1 Institute of Physics, Czech Academy of Sciences, Prague, Czech Republic 2Department of Physics, Northern Illinois University, DeKalb, IL, USA

3Institute of Nanoscience of Aragón, University of Zaragoza, Spain *Corresponding Author: goian@fzu.cz

In recent first principles calculations a large spin-phonon coupling in various manganites, chromides and ferrites with perovskite structure was predicted [1], so these materials can theoretically become new multiferroics under strain or with appropriate doping. In this work, we will focus on Sr1-xBaxMn1-yTiyO3 (x=0.45, 0.5 and 0.6 and y=0, 0.06 and 0.1) perovskite ceramics where we will demonstrate phonon anomalies near ferroelectric and antiferromagnetic phase transitions. Pure SrMnO3 is paraelectric down to liquid He temperatures, crystallizes in cubic perovskite P mm3 crystal structure and exhibits magnetic phase transition to antiferromagnetic G-type phase near 230 K [2]. Close to this temperature 23% hardening of the lowest-frequency phonon was revealed in the IR spectra due to spin-phonon coupling [3]. By partially substituting of Sr by Ba, the Sr1-xBaxMnO3 (x > 0.40) becomes ferroelectric with TC | 400 K and Néel temperature TN | 200 K. Important fact is that in this case the strong ferroelectric polarization (PS = 13 PC/cm2 ) is caused by displacement of magnetic Mn4+ cations, so exceptionally strong magnetoelectric coupling is expected [4,5]. We will show that the ferroelectric phase transition in Sr0.55Ba0.45MnO3 exhibits a crossover between displacive type and order-disorder one. The optical soft mode softens on heating towards TC, but its dielectric strength is quite small, so the observed dielectric anomaly in the THz region is rather weak. The central mode (CM) in the microwave region drives the phase transition near TC. No changes in the THz permittivity spectra with magnetic field up to 7 T were observed [6]. Unfortunately, the conductivity influences the MW and THz permittivity in Sr0.55Ba0.45MnO3 ceramics. Hopping conductivity can be strongly reduced by Ti doping. For that reason we investigated Sr1-xBaxMn1-yTiyO3 ceramics, where y=0.06 and 0.1 and x= 0.6 and 0.5. Microwave permittivity and conductivity is still influenced by Maxwell-Wagner relaxation, but permittivity of Sr0.4Ba0.6Mn0.94Ti0.06O3 exhibits a peak at ferroelectric phase transition near 400 K. Ferroelectric phase transition is seen as well in phonon permittivity obtained from the fits of THz and IR reflectivity spectra. The soft mode slightly softens and a strong CM appears near TC. Spin-phonon coupling is manifested by the jump of THz permittivity near TN. THz permittivity of Sr0.4Ba0.6Mn0.94Ti0.06O3 ceramics was measured in external magnetic field up to 7 T. Like in Sr0.55Ba0.45MnO3, no magnetodielectric effect was observed, which is rather surprising, because large magnetoelectric effect is theoretically expected. We explain it by absence of ferromagnetic state and by the high stability of the Néel temperature in magnetic field.

In Sr0.6Ba0.4MnO3 thin films deposited using Pulsed Laser Deposition on (LaAlO3)0.3(Sr2TaAlO6)0.7 (LSAT) and TbScO3 substrates, no ferroelectric phase transitions were detected in microwave spectra. In Sr0.6Ba0.4MnO3/LSAT, antiferromagnetic phase transition was observed near 160 K. Strain effect on multiferroic properties of Sr1-xBaxMnO3 thin films will be discussed. References [1] J. Hong et al., Phys. Rev. B 85, 054417 (2012). [2] O. Chmaissem et al., Phys Rev. B 64, 134412 (2001). [3] S. Kamba et al., Phys. Rev. B 89, 064308 (2014). [4] H. Sakai et al. Phys. Rev. Lett. 107, 137601 (2011). [5] H. Sakai et al. Phys. Rev. B 86, 104407 (2012). [6] V. Goian et al. J. Phys.: Condens. Mater. 28, 175901 (2016).

Crystallisation in Potassium Sodium Niobate-based Glass-Ceramics

Abdulkarim Z. Khalf,1,*

and David A. Hall1

1School of Materials, University of Manchester, Manchester, UK

*abdulkarim.khalf@postgrad.manchester.ac.uk

Glass-ceramics containing ferroelectric (K0.5

Na0.5

)NbO3

(KNN) can potentially combine the

desirable characteristics of glasses and ferroelectric crystals, giving rise to novel materials having

pore-free and fine-grained microstructures; such materials have potential applications in high energy

density capacitors and electro-optic devices[1,2]. Glass-ceramic samples were prepared by a

conventional melt-quenching method using the low-melting point barium borosilicate glass, 20BaO-

40B2O

3-20SiO

2-10K

2O-10Na

2O (BBSKN), with KNN contents ranging from 30 to 80 mol%. The

amorphous nature of the quenched glasses was confirmed using XRD. Several KNN-BBSKN glass

samples were subsequently heat-treated over a range of temperatures up to 900 °C. The occurrence of

the crystallisation process and the nature of the resulting phases was examined using DSC, XRD and

SEM.

The DSC results showed the presence of an exothermic peak at a temperature of 630 °C,

indicating the precipitation of crystalline phases from the amorphous glass matrix. This observation

was supported by the corresponding XRD patterns at this temperature, in which the development of

crystalline perovskite KNN and barium silicate phases could be clearly detected (Figure 1(a)).

Examination by SEM revealed that the crystalline phases had a very fine particle size and were well-

dispersed within the glassy matrix. Preliminary results from dielectric and ferroelectric measurements

indicated that the dielectric behaviour of the glass-ceramics was predominantly linear, with relative

permittivities in the range 70 to 120 at room temperature (Figure 1(b)).

Figure 1(a). XRD patterns of 70KNNglass-ceramic sample heated up to 800°C for 4h. And (b)

dielectric permittivity with temperature of 50KNN and 70KNN heated at 700 and 800°C for 4h.

References [1] P. Yongsiri, S. Eitssayeam, S. Sirisoonthorn and K. Pengpat. "Morphology of Potassium

Sodium Niobate based Silicate Glass System“, Electron. Mater. Lett., Vol. 9, No. 6 (2013), pp. 825-827.

[2] P. Yongsiri, S. Sirisoonthorn, K. Pengpat , ‘’Effect of Er2O3 dopant on electrical and optical properties of potassium sodium niobate silicate glass-ceramics’’, Materials Research Bulletin 69 (2015) 84–91.

(a) (b)

Zero-point renormalization and temperature dependence of

the LiNbO3 band gap from first principles

M. Friedrich, A. Riefer, S. Sanna, W. G. Schmidt, and A. Schindlmayr

Department Physik, Universität Paderborn, 33095 Paderborn, Germany *Corresponding Author: michael.friedrich@upb.de

Lithium niobate (LiNbO3) is a dielectric crystal with outstanding electro-optical properties that is widely used for optical waveguides and other commercial applications. As previous experimental and theoretical studies have mostly concentrated on the ground-state properties, the variation of technologically important material parameters with the temperature, which stems from the coupling to phonons, has received little attention until now. Here we perform quantitative calculations within density-functional perturbation theory (DFPT) as well as ab initio molecular dynamics (MD) in order to evaluate the vibrational contributions to the LiNbO3 fundamental band gap.

Figure 1. Temperature-dependent shift of the fundamental absorption edge from DFPT and

molecular dynamics compared to experimental results.

Our work reveals a correction of the electronic eigenvalues, that is strongly dependent on the phonon wave vector. Our results indicate a large shift of 0.4 eV due to the zero-point renormalization [1] and an additional temperature-dependent variation of the band gap [2], both in excellent agreement with the available experimental data [3]. Altogether, vibrational effects thus lead to a reduction of the band gap of 0.5 eV at room temperature. The agreement between the experimental data and the theoretical curve from DFPT is excellent in the low temperature regime due to the proper inclusion of the zero-point motion of the lattice. At higher temperatures, molecular dynamics provide a better description of the lattice vibrations because anharmonicities are taken into account.

References [1] M. Friedrich et al., J. Phys.: Condens. Matter 27, 385402 (2015). [2] A. Riefer et al., Phys. Rev. B 93, 075205 (2016). [3] D. Redfield and W. J. Burke, Appl. Phys. 45, 4566 (1974).

0 200 400 600 800 1000Temperature (K)

-1

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

Shift

of t

he a

bsor

ptio

n ed

ge (e

V)

DFPTMDExperiment [3]Expt. fitExpt. asymptote

Lead-Free multi-layered Actuators for High Temperature Applications

Amir Khesro1, Dawei Wang1, Fayaz Hussain1, Antonio Feteira2, Derek C Sinclair1 and Ian M Reaney1

1 Functional Materials and Devices, Materials Science and Engineering, Sir Robert Hadfield Building, University of Sheffield, Sheffield, S1 3JD, UK. 2 Materials and Engineering Research Institute, Sheffield Hallam University, Howard Street, Sheffield, S1 1WB, UK.

*Corresponding Author: amir.khesro@sheffield.ac.uk

A piezoelectric actuator converts an electrical signal into a precisely controlled mechanical strain. The ability to control physical displacements with high precision makes piezoelectric actuators vital for many applications such as cameras, phones, microscopes, fuel injectors, micro-pumps, ink cartridges and medical surgery instruments1. Pb(Zr,Ti)O3 (PZT)-based ceramics are most widely used ceramics for actuators by virtue of their large piezoelectric and electromechanical coupling coefficients, ease of fabrication and cost2. However, health and environmental concerns over the use of lead has challenged researchers to fabricate lead-free piezoelectric materials with properties comparable to those based on PZT. The actuator technology relies on multi-layered structures as they can be operated at low voltages. Many technological devices such as fuel injectors have harsh operating environments3 well above room temperature and hence the temperature dependence of functional properties is important if the material is to be used for real world applications. We have recently developed lead free ceramics and have fabricated them successfully to prototype multilayer structures capable of giving stable output strains up to 300 °C. The results are very promising and these materials can be potentially useful for future lead free actuators.

References [1] W. Jo, R. Dittmer, M. Acosta, J. Zang, C. Groh, E. Sapper, K. Wang, and J. Rödel, Journal

of Electroceramics 29 (1), 71 (2012). [2] D. Damjanovic, N. Klein, J. I. N. Li, and V. Porokhonskyy, Functional Materials Letters 03

(01), 5 (2010). [3] R. Müller-Fiedler and V. Knoblauch, Microelectron. Reliab. 43, 1085 (2003)

Enhanced piezo response in mechanical activated and microwave sintered PLZT 8/60/40 ceramics

Ajeet Kumar,1 K. C. James Raju,1 A R James2,*

1School of physics, University of Hyderabad, Hyderabad, India-500046 2CCG, Defence Metallurgical Research Laboratory, Hyderabad, India-500058

*Corresponding Author: james@dmrl.drdo.in PLZT 8/60/40 ceramics, which show ultra high piezoelectric properties, are widely used for

numerous devices. Like other lead based ceramics, PLZT ceramics also have a tendency of lead loss at higher calcination and sintering temperatures. In this present study, lead volatility issue is addressed by the combinatorial approach of high energy ball milling and microwave sintering. This approach helps to enhance the densification and electrical properties. High energy mechano-chemical ball milling results in ultrafine powders with a narrow particle size distribution that leads to reactions of oxide precursors which are activated by mechanical energy, which brings down the ceramic processing temperatures. Microwave heating is a method of internal self heating through absorption of microwave radiation. Due to the volumetric and material dependent nature, microwave sintering takes less time at low temperature.

Figure 1. (a) P-E (b) I-E and (c) S-E ferroelectric loops of microwave sintered PLZT

ceramics The XRD pattern and SEM image were used for the micro-structural characterization of

mechanically activated and microwave sintered PLZT 8/60/40 ceramics. Higher relative density (~99.46%) and more uniform grain distribution (~1.2 µm) were found for PLZT ceramics which was microwave sintered at 1150oC. The dielectric constant for the unpoled PLZT ceramics was found to be ~2100 at 1 kHz frequency with very low dielectric loss (~0.03). The saturated P-E and S-E ferroelectric hysteresis loops as well as the domain switching current peak in I-E loop (fig.1(a)) confirms the ferroelectric nature of PLZT ceramics. The highest value of Pr~33 µC/cm2, Ec~10 kV/cm and strain~0.26, was found for the ceramics which was microwave sintered at 1150oC. The piezoelectric charge (d33) and electromechanical coupling coefficient (kp) value for the PLZT ceramics were found to be, ~575 pC/N and ~67%, respectively.

References [1] A. Kumar, S.R. Emani, V.V.B. Prasad, K.C.J. Raju and A.R. James, J. Euro. Ceram. Soc., 36, 2505-2511 (2016) [2] P.K. Sharma et al., Smart Mater. Struct., 10, 878-83 (2001) [3] Z. Xie, Z. Gui, L. Li, T. Su and Y. Huang, Mater. Lett., 36, 191-194 (1998)

Nanoscale polarization relaxation and piezoelectric properties of SBN thin films M. Melo1, E. B. Araujo1*, M. Ivanov2, V. Ya. Shur3 and A. L. Kholkin2,3

1Department of Physics and Chemistry, São Paulo State University,

15385-000 Ilha Solteira, SP, Brazil 2Department of Physics & CICECO – Aveiro Institute of Materials, University of Aveiro,

3810-193 Aveiro, Portugal 3Institute of Natural Sciences, Ural Federal University, 620000 Ekaterinburg, Russia

*Corresponding Author: eudes@dfq.feis.unesp.br The strontium barium niobate SrxBa1-xNb2O6 (SBN) is a promising ferroelectric material for

a number of technological applications due to its excellent pyroelectric coefficient, piezoelectric and electro-optic properties. The composition x = 0.75 exhibit a typical relaxor feature and is particularly important because most of its photorefractive properties have potential for technological applications. Relaxor behavior is always accompanied by structural and related charge disorder as well as the existence of relaxing entities such as polar nanoregions (PNRs). Among techniques to explore ferroelectric surface on the micron and nanometer levels, piezoelectric force microscopy (PFM) have been used for polarization mapping on the surface and to quantitative studies on the short-range nanopolar clusters are long-range ferroelectric order in relaxors [1]. In the present work, random oriented Sr0.75Ba0.25Nb2O6 thin films has been deposited on Pt(111)/Ti/SiO2/Si substrates using a polymeric chemical route to study their peculiar nanopolar structures and local ferroelectric properties using PFM technique. Details on the synthesis, structural and dielectric properties of these SBN films can be found elsewhere [2]. PFM images of the as-grown films reveal grains with contrast among fully white and fully black, a clear indication of non-zero polarization in the SBN films well above the Tm ~ 221 K. The distribution of the piezoresponse signal slightly shifts towards the negative voltage values (푑 = −0.08 V), suggesting an imprint effect in the studied films. This effect is also confirmed by asymmetries observed in macro scale hysteresis loops as well in local piezoresponse hysteresis loops recorded at different grains. Some grains shows asymmetric local hysteresis loops while other grains shows symmetric hysteresis loops. The origin of the imprint effect observed in the SBN films is discussed in terms of defect-dipole complexes associated to oxygen vacancies. PFM-based relaxation experiments were conducted applying pulses of +5, +10, +15 and +20 Volts to the probe for 10, 100, 500, 1000 and 3000 ms. The obtained relaxation curves were fitted using the equation 푃 = 푃 exp (−푡/휏) + 퐶, where P is the piezoelectric signal, P0 is the relaxation amplitude, 휏 is the time constant and C is the nonrelaxing component. The obtained time constant 휏 increases from 785 to 977 ms as the magnitude voltage increases. The polarization relaxation in the studied relaxor SBN film is discussed in terms of inhomogeneous polarization observed on the film surface.

References [1] V.V. Shvartsman, B. Dkhil, A.L. Kholkin. Annu. Rev. Mater. Res. 43, 423 (2013). [2] M. Melo, E. B. Araujo, A. Turygin, V. Shur, A. Kholkin. Ferroelectrics 496, 177 (2016).

Composition and Temperature Dependence of Piezoelectricity in KNN-base Lead-Free Ceramics

D. Wang1, F. Hussain1, A. Khesro1, A. Feteira2, Y. Tian3, and I. M Reaney1,*1Department of Materials Science and Engineering, University of Sheffield, Sheffield S1 3JD,

UK2Christian Doppler Laboratory for Advanced Ferroic Oxides, Sheffield Hallam University,

Sheffield S1 1WB, UK3School of Engineering and Materials Science, Queen Mary University of London, London E1

4NS, UK*Corresponding Author: i.m.reaney@sheffield.ac.uk

Lead-free piezoceramics with the composition (1-x)(K1-yNay)NbO3-x(Bi1/2Na1/2)ZrO3

(KNyN-xBNZ) were prepared using a conventional solid state route. X ray diffraction, Ramanspectroscopy and impedance measurements as a function of temperature indicated thecoexistence of rhombohedral (R) and tetragonal (T) phase, typical of a morphotropic phaseboundary (MPB) as the BNZ concentration increased and by adjusting the K/Na ratio. Highremnant polarization (Pr = 24 μ C/cm2), piezoelectric coefficient (d33 = 320 pC/N), effectivepiezocoefficient (d33* = 420 pm/V), coupling coefficient (kp = 48%) and high strain (S = 0.168%)were obtained at room temperature (RT) but significant deterioration of Pr, d33* and kp wereobserved by increasing from RT to 160 °C (17.5 μC/cm2, 338 pm/V and 32%, respectively)associated with a transition to a purely T phase. Despite these compositions showing promise forRT applications, the deterioration in properties as a function of increasing temperature poseschallenges for device design and remains to be resolved.

Figure 1. R-T MPB construction and temperature dependence in KNN-BNZ cermiacs

Substitution of B-site ions with Mn in PIN-PMN-PT: Influence on properties L. A. Stoica1,* and A. J. Bell1

1School of Chemical and Process Engineering, University of Leeds, Clarendon Road, Leeds, United Kingdom, LS2 9JT

*Corresponding Author: sm11las@leeds.ac.uk

Piezoelectric materials with low energy losses are required for high power devices to minimise the unwanted heating effect. It has been shown that Mn modifications (typically in the range 0.5-2mol%) significantly enhance Qm in PbTiO3-based polycrystalline and multi domain single crystal ceramics. Although studies suggest the presence of Mn with 2+, 3+ and 4+ valence states, it is commonly assumed that only Mn2+ has an impact on enhancing Qm via !"!"!! − !!•• defect dipole formation and consequent pinning of domain wall movement. The present study investigates the influence of chemical environment in 2mol%Mn-modified Pb(In1/2Nb1/2)O3- Pb(Mg1/3Nb2/3)O3-PbTiO3 polycrystalline samples on properties. A number of compositions have been investigated and it has been assumed that Mn occupies the B-site of the perovskite lattice. For each composition prepared, 2mol%Mn substitutes sequentially 2mol% In, Mg, Ti and Nb. X-ray absorption near edge structure has been used to gain insights into the valence state of Mn. Polarisation versus electric field loops allowed the identification of any internal bias fields. Furthermore, impedance spectroscopy has been used to explore the frequency response of the samples and to identify the conduction mechanisms. The results suggest the presence of Mn under multiple valence states. Internal bias fields of different magnitudes have been observed in all samples. Complex impedance measurements revealed a non-ideal behavior described by an R-CPE equivalent circuit. A distribution of relaxation times is present and the !width of the distribution is broader for samples where Nb content is lower. The relaxation arises from the bulk and grain boundaries. A combination of conductivity mechanisms is observed: electronic via polaron hopping and ionic via oxygen vacancies diffusion. Small changes in the concentration of B-site ions also affects Qm. Although all investigated samples have been modified with the same amount of Mn, i.e. 2mol%, the different overall compositions caused dissimilar behaviour. Different concentrations of various B-site ions seem to play an important role on the properties of Mn-modified samples. Further research should be undertaken to clarify the mechanisms by which the different ions influence the behaviour of Mn modified perovskites.

Substitution of B-site ions with Mn in PIN-PMN-PT: Influence on properties L. A. Stoica1,* and A. J. Bell1

1School of Chemical and Process Engineering, University of Leeds, Clarendon Road, Leeds, United Kingdom, LS2 9JT

*Corresponding Author: sm11las@leeds.ac.uk

Piezoelectric materials with low energy losses are required for high power devices to minimise the unwanted heating effect. It has been shown that Mn modifications (typically in the range 0.5-2mol%) significantly enhance Qm in PbTiO3-based polycrystalline and multi domain single crystal ceramics. Although studies suggest the presence of Mn with 2+, 3+ and 4+ valence states, it is commonly assumed that only Mn2+ has an impact on enhancing Qm via !"!"!! − !!•• defect dipole formation and consequent pinning of domain wall movement. The present study investigates the influence of chemical environment in 2mol%Mn-modified Pb(In1/2Nb1/2)O3- Pb(Mg1/3Nb2/3)O3-PbTiO3 polycrystalline samples on properties. A number of compositions have been investigated and it has been assumed that Mn occupies the B-site of the perovskite lattice. For each composition prepared, 2mol%Mn substitutes sequentially 2mol% In, Mg, Ti and Nb. X-ray absorption near edge structure has been used to gain insights into the valence state of Mn. Polarisation versus electric field loops allowed the identification of any internal bias fields. Furthermore, impedance spectroscopy has been used to explore the frequency response of the samples and to identify the conduction mechanisms. The results suggest the presence of Mn under multiple valence states. Internal bias fields of different magnitudes have been observed in all samples. Complex impedance measurements revealed a non-ideal behavior described by an R-CPE equivalent circuit. A distribution of relaxation times is present and the !width of the distribution is broader for samples where Nb content is lower. The relaxation arises from the bulk and grain boundaries. A combination of conductivity mechanisms is observed: electronic via polaron hopping and ionic via oxygen vacancies diffusion. Small changes in the concentration of B-site ions also affects Qm. Although all investigated samples have been modified with the same amount of Mn, i.e. 2mol%, the different overall compositions caused dissimilar behaviour. Different concentrations of various B-site ions seem to play an important role on the properties of Mn-modified samples. Further research should be undertaken to clarify the mechanisms by which the different ions influence the behaviour of Mn modified perovskites.

Effects of electrostriction, flexoelectricity and chemical pressure on polarization switching kinetics in thin ferroelectric films

Ivan S. Vorotiahin1*, Yuri A. Genenko,1 and Anna N. Morozovska2 1Institut für Materialwissenschaft, Technische Universität Darmstadt, Jovanka-Bontschits-Str. 2,

Darmstadt, Germany 2Institute of Physics, National Academy of Sciences of Ukraine, pr. Nauky 46, Kyiv, Ukraine

*Corresponding Author: genenko@mm.tu-darmstadt.de Electrostriction effect is known to have a significant influence on ferroelectric phase

transitions1. It affects the transition temperature, the magnitude of the spontaneous polarization and is able to change the type of the phase transition. Account of further electromechanical effects like flexoelectricity and Vegard strains (chemical pressure) becomes especially important at the nanoscale2. In this contribution, the effect of the mentioned phenomena on polarization switching kinetics in thin ferroelectric films is considered using a time dependent Landau-Ginzburg-Devonshire (T-LGD) approach. As an example a thin barium titanate film doped with donors (oxygen vacancies) is studied in one-dimensional (1D) approximation. The combined electromechanical and semiconductor (space-charge) effects as well as the choice of boundary conditions on polarization and strain are shown to have a great impact on the formation of single- or multi-domain states, the coercive field and the kinetics of polarization reversal. In particular, the polarization reversal kinetics is governed by the phonon relaxation time included in T-LGD equation only when the donor's kinetic is very fast and thus can be considered in adiabatic approximation. Otherwise the polarization kinetics is strongly affected by the donors' mobility, redistribution and surface chemistry.

Figure 1. Polarization development with time in a thin (100 nm) barium titanate film with (solid line) or without (dashed line) account of the flexoelectric effect. The first stage of the process (until the normalized time 1) depicts formation of the spontaneous polarization, the

second stage shows polarization reversal when an opposite electric field is applied.

References [1] N.A. Pertsev, A.G. Zembilgotov, and A.K. Tagantsev, Phys. Rev. Lett, 80, 1988 (1998) [2] A.N. Morozovska, E.A. Eliseev, A.K. Tagantsev, S.L. Bravina, Long-Qing Chen, and S.V. Kalinin, Phys. Rev., 83, 195313 (2011)

Titanium-Dioxide Ceramic: Unique High Permittivity and Ultra-Low Loss Terahertz Material

Chuying Yu1, Yang Zeng2, Bin Yang2*, Jinbao Huang3, Robert Donnan2, Zhaoxian Xiong3, Baogui Shi4, Haitao Ye4, Russell Binions1, Mike J Reece1 and Haixue Yan1*

1 School of Engineering and Materials Science,Queen Mary, University of London, E1 4NS, United Kingdom

2 School of Electronic Engineering and Computer Science, Queen Mary, University of London, E1 4NS, United Kingdom

3 College of Materials, Xiamen University, Simen Road, Xiamen 361005, China 4 School of Engineering and Applied Science, Aston University, Birmingham, B4 7ET, United

Kingdom *Corresponding Author: b.yang@chester.ac.uk; h.x.yan@qmul.ac.uk

The Terahertz (THz) band, loosely defined as the electromagnetic frequency range from 0.1

to 10 THz, has attracted considerable interest in the last two decades due to its attractive applications in material, chemical, communication and life sciences 1,2. However, the lack of THz materials with ultra-low loss and high dielectric constant materials is a major constraining factor in the further development of THz technologies 3,4. In the present work, TiO2 has been investigated as THz material due to its high dielectric permittivity (ca. 100) 5. However, the processing of TiO2 is very sensitivity to temperature and oxygen partial pressure. It is found that ceramics produced by conventional sintering method were high in loss due to the formation of trapped porosity linked with defects and second phase. Here an advanced technique-Spark Plasma Sintering (SPS) was adopted to produce denser ceramics without closed porosity and second phase. Ceramics with high permittivity (εr=95.01 at 0.22 THz and εr=97.635 at 0.325 THz) and ultra-low loss (0.0053 at 0.22 THz and 0.00624 at 0.325 THz) in the THz band were fabricated (shown in Figure 1). This is a significant step change as its broadband low loss and additionally high permittivity properties are beyond the applications of commercial high-resistivity Silicon wafers (εr=11) 6 .

Figure 1. Frequency dependence of dielectric properties in Spark Plasma Sintering (SPS)

samples in THz domain (0.22THz-0.325THz)

References [1] Nagel, M et al., Applied Physics Letters, 80, 154 (2002). [2] Ferguson, B et al., Nature materials, 1, 26 (2002). [3] Shalaby, M et al., Nature communications, 4, 1558 (2013). [4] Chen, H.-T et al., Nature Photonics, 3, 148 (2009). [5] Grant, F. Reviews of Modern Physics, 31, 646 (1959). [6] Sun, W et al., Optics letters, 38, 5438 (2013).

Giant Electrostrains in Bismuth-Alkali-Based Perovskite Oxides Xiaoming Liu and Xiaoli Tan*

Department of Materials Science and Engineering, Iowa State University, Ames, Iowa, USA *Corresponding Author: xtan@iastate.edu

(Bi1/2Na1/2)TiO3-based lead-free piezoceramics are more likely to display large electric field-

induced strains compared with other solid solution systems. In this study, the electric field-induced strains and temperature changes were evaluated in two series of ceramic compositions. The polycrystalline ceramic ^[Bi1/2(Na0.84K0.16)1/2]0.96Sr0.04`(Ti0.975Nb0.025)O3 was observed to display a giant electrostrain of 0.70% at 50 kV/cm at room temperature, corresponding to a remarkable d33* value of 1400 pm/V [1]. To clearly compare these properties of bulk lead-free oxides, data from previous literature was compiled in a strain vs. d33* plot, shown in Figure 1. Lead-containing ferroelectric ceramics are also included as reference. It is clear that single crystals in the bismuth-alkali titanate family stand out for both large electrostrain and high d33*. Our polycrystalline ceramic with randomly oriented grains is even better than some single crystals in terms of these properties. In-situ transmission electron microscopy examination indicates that the giant electrostrain is originated from the phase transitions under applied electric fields.

Figure 1. Comparison of lead-free solid solution families against their electrostrains and d33*. In the second series, [Bi1/2(Na0.8K0.2)1/2](Ti0.985Ta0.015)O3 was found to display an electrostrain

of 0.62%, corresponding to a large-signal piezoelectric coefficient d33* of 1240 pm/V [2]. This ceramic displays low cycling degradation; its electrostrain remains above 0.55% even after undergoing 10,000 cycles of bipolar fields of r50 kV/cm at 2 Hz.

References [1] X.M. Liu and X. Tan, Advanced Materials, 28, 574-578 (2016). [2] X.M. Liu and X. Tan, Journal of Applied Physics, submitted, 2016.

Pyroelectricity in Hf1-xZrxO2 thin films S. W. Smith1, A. Kitahara1, M. D. Henry,1 M. B. Sinclair,1 M. T. Brumbach,1 M. A.

Rodriguez,1 and J. F. Ihlefeld1 1Sandia National Laboratories, P.O. Box 5800, M.S. 1411, Albuquerque, New Mexico 87185,

United States *Corresponding Author: Ssmith5@sandia.gov

Switchable polarization in HfO2-based thin films was first reported in 2011 and has since

been shown with a variety of dopants.1 Material, process and thickness compatibility with current silicon microelectronic processing make it an appealing alternative to traditional ferroelectrics for a variety of applications. A growing body of literature supports true ferroelectric response, including piezoelectricity, and, recently, pyroelectricity. HfO2-based materials are particularly attractive for pyroelectric applications owing to low dielectric constant, relative to other ferroelectrics. Pyroelectric reports to date utilize P(E) measurements at differing temperatures or measured current during heating. 2 These measurements may contain artifacts that mask the true response. Here, we explore the pyroelectric response in ALD-prepared Hf1-xZrxO2 films using a cyclic heating and cooling technique that allows decoupling of true pyroelectric response from thermally stimulated currents.

Figure 1(a) shows nested polarization loops measured at 1 kHz for 20 nm thick Hf0.5Zr0.5O2 with TaN electrodes. Clear polarization hysteresis (leakage precludes measurement of remanent polarization) with a coercive field of about 1 MV/cm is observed. Figure 1(b) shows pyroelectric measurements for for 20 nm Hf0.5Zr0.5O2 with TaN electrodes. The temperature and current signals are approximately 90° out of phase indicating a strong pyroelectric component to the current with a pyroelectric coefficient of 40 µCm-2K-1, comparable to LiNbO3 and PVDF. This work will explore the influence of film thickness, composition, and phase on pyroelectric performance in Hf0.5Zr0.5O2. Sandia National Laboratories is a multiprogram laboratory operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Company, for the United States Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

Figure 1. a) Nested polarization vs. electric field loops for 20 nm Hf0.5Zr0.5O2 and b) Pyroelectric measurement for 20 nm Hf0.5Zr0.5O2 showing current and temperature osscillations are out of phase

References [1] M. H. Park, Y. H. Lee, H. J. Kim, Y. J. Kim, T. Moon, K. D. Kim, J. Mueller, A. Kersch, U. Schroeder, T. Mikilajick, C. S. Hwang. Advanced Materials, 27, 1811-1831 (2015) [2] M. H. Park, H. J. Kim, Y. J. Kim, T. Moon, K. D. Kim, C. S. Hwang, Nanoenergy, 12, 131-140 (2015)

Dynamics of ferroelectric switching in relaxor ferroelectric strontium-barium niobate crystals via scanning probe microscopy

L.V. Simagina*, R.V. Gainutdinov, and T.R.Volk Shubnikov Institute of Crystallography, Leninsky pr. 59, Moscow, Russia

*Corresponding Author: lsimagina@gmail.com

The results of intensive studies of ferroelectric switching and domain recording carried out

by means of scanning probe microscopy (SPM) are presented for crystals of Sr0.61Ba0.39Nb2O6 (SBN). The domain arrays engineering for potential nonlinear optical applications requires detailed researches of domain evolution under SPM-tip fields.

With the use of SPM we analyzed, for the first time to our knowledge, the contribution from backswitching to polarization reversal under SPM-tip voltages in SBN crystals. Domain dynamics and local piezoelectric hysteresis (Hω-U) loops (where Hω is the electromechanical response signal) were studied both on the polar (c-) and nonpolar (a-) crystal surfaces.

Fig. 1 presents the loops obtained in a pulse dc-mode in range of ±10 V with further PFM-signal sensing The parameters of (Hω-U) loops strongly depend on the field-pulse duration tp and space time Δt between pulses. At constant tp (1-1000 ms) the loop amplitudes, i.e. the remnant polarization Pr contracted while increasing Δt (fig. 1(a)). Similarly, with decreasing tp at a constant Δt a pronounced decrease of Pr occurs (fig. 1(b)). At tp=1000 ms the pulse space no more affects the loop amplitude. The loop half-width, i.e. Ec depends on the pulse ratio as well. Namely, with increasing Δt at a constant tp the growth of Ec was detected, whereas at a constant Δt the increase of tp from 40 to 1000 ms resulted in a loop narrowing.

We attribute the observed effects to backswitching phenomena [1]. In this regard, tp=1000 ms characterizes so-called “stabilization time” ts required for occurring of a stable switched region. The estimates of ts in switching studies on the nonpolar SBN surfaces [2] gave similar ts of about few minutes. These times exceed by orders of magnitude ts reported for usual (uniform) ferroelectrics (e. g. TGS or LiNbO3 [3]), which is obviously related to the relaxor features of SBN. The origin of the observed backswitching can be discussed either in terms of domain-wall pinning-depinning, or screening effects [1]. Both approaches are compatible with relaxor nature of SBN crystals and complementary to each other.

a b

Figure 1. Piezoelectric hysteresis (Hω-U) loops for SBN crystal (c-cut) for different

parameters of pulse train. This work was supported by RFBR (project N 16-32-00319).

References [1] A.K. Tagantsev, L.E. Cross, and J. Fousek. Domains in Ferroic Crystals and Thin Films, Springer Science NY, 821 p. (2010) [2] T. R. Volk, R. V. Gainutdinov, Ya. V. Bodnarchuk, and L. I. Ivleva, JETP Letters, 97 (8), 483–489 (2013) [3] Volk T., Wöhlecke M. Lithium Niobate: Defects, Photorefraction and Ferroelectric Switching, Berlin: Springer, Springer Series in Materials, 249 p. (2008).

Piezoelectric properties of textured BNKT ceramics prepared by reactive-templated grain growth using Bi4.5Na0.5Ti4O15 and Bi0.5Na0.5TiO3 templates

Hyun Ae Cha and Jae-Ho Jeon *

Funtional Nanopowder Materials Dept., Korea Institute of Materials Science, Changwon, Korea *Corresponding Author: jjh@kims.re.kr

Textured Bi0.5(Na0.8K0.2)0.5TiO3 (BNKT) ceramics were prepared by reactive-templated grain

growth using Bi4.5Na0.5Ti4O15 (BNT15) and Bi0.5Na0.5TiO3 (BNT) templates. BNT15 and BNT

templates were synthesized by Topochemical Microcrystal Conversion (TMC) method using

plate-like Bi4Ti3O12 (BiT) precursor. The synthesized BNT has a mixture of both equiaxed and

plate-like particles whereas only plate-like BNT15 particles are formed. The difference in the

conversion mechanism between the BNT and BNT15 templates during TMC is believed to be

due to a difference in the role of TiO2 that depends on the crystal structure of perovskite BNT

and Aurivillius BNT15. When the amount of BNT15 and BNT templates was added so that 20%

of Ti in the textured BNKT supplied from these templates, grain orientation degree (Lotgering

factor) and piezoelectric constant (d33) of textured BNKT by BNT15 template are higher than

those of textured BNKT by BNT template. On the other hand, when 20% of Ti in the textured

BNKT was supplied from plate-like BNT particle, Lotgering factor and d33 of textured BNKT

were similar to those of textured BNKT by BNT15 template. Since these results indicated that

only the plate-like BNT particle contributed to the texturing of BNKT ceramics, the optimum

amount of BNT template should be carefully designed when textured BNKT ceramics were

prepared by BNT template.

0

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100

plate BNTBNT

Lote

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Fact

or (%

)

BNT150

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/N)

Figure 1. Lotgering factor and piezoelectric constant of textured BNKT ceramics by BNT15,

BNT, and plate BNT template.

References [1] J. T. Zeng et al., J. Am. Ceram. Soc., 89, 3850-3853 (2006)

[2] Wei Zhao et al., J. Am. Ceram. Soc., 91, 1322-1325 (2008)

[3] P. Setasuwon et al., Mater Lett., 64, 1157-1159 (2010)

Photovoltaic effect in PbTiO3-Bi(Ni2/3+xNb1/3-x)O3-δ ferroelectrics Hui Liu,1 Jun Chen,1,* Yang Ren,2 Linxing Zhang,1 Zhao Pan,1 Longlong Fan,1 and

Xianran Xing1 1 Department of Physical Chemistry, University of Science and Technology Beijing, Xueyuan Road 30,

Beijing, China 2 Argonne National Laboratory, X-Ray Science Division, Argonne, Illinois, USA

*Corresponding Author: junchen@ustb.edu.cn The ferroelectric photovoltaic is a novel effect which allows well above the band gap and

might enable efficiencies beyond the maximum possible in a conventional p-n junction solar cell[1]. However, the photoelectric conversion performance in most ferroelectric photovoltaic materials is still too low due to wide band gap or low polarization properties.[2,3] Here, we have reported a new ferroelectric perovskites PbTiO3-Bi(Ni2/3+xNb1/3-x)O3-δ (PT-BNN), which is designed according to the photovoltaic requirements of polarization and band gap. We have obtained a relatively low bandgap (2.3 eV) and a relatively large remnant polarization (33 μC/cm2) by chemical substitution of BNN in PT ferroelectric. In the Pt/PT-BNN/Ag sandwich electrode configuration, a large photovoltage of 10 V (20 kV/cm) is achieved under visible wavelength illumination. Moreover, the direction and the magnitude of the photovoltaic output are controllable with the direction of poling electric field and the stoichiometric ratio of Ni and Nb, respectively. The present study not only offers a new system for the potential application in solar energy cells, but also provides a method to explore good photovoltaic performance in ferroelectric materials.

References [1] Yang S. Y. et al., Nature Nanotech., 5, 143-147 (2010) [2] Yuan Y. et al., J. Mater. Chem. A, 2, 6027-6041 (2014) [3] Grinberg I. et al., Nature, 503, 509-512(2013)

Nonliear Harmonic Generation by Optimization of Microstructured Crystals

Yiqiang Qin*, Ding Zhu, Chao Zhang

National Laboratory of Solid State Microstructures, Nanjing University, Nanjing 210093, China

*Corresponding Author: yqqin@nju.edu.cn For quasi-phase-matching (QPM) technique, much research has been done for purpose of

obtaining efficient frequency conversion where the largest nonlinear coefficient (corresponding to ee eo process) is used. However, these crystals do have other considerable nonlinear coefficients. In these cases, QPM parametric interactions such as oo eo , oe oo and eo eo process can be realized efficiently. From the viewpoint of coupling, the conventional harmonic generation with largest nonlinear coefficient should be treated as a particular case, the coupling of second-order parametric interactions based on different nonlinear second-order processes could be considered as a more general situation.

We concentrate on the cascading third harmonic generation (THG) with domain engineered micro-structures. To investigate the QPM nonlinear interactions by coupling of non- ee eo processes, we select cascaded 1 1 2o e oo (SHG) and 1 2 3o o eo (SFG) processes for THG as an example. 1 1 2o e oo process generates y-polarized second harmonic (SH) using both ordinary and extraordinary components of the fundamental, while

1 2 3o o eo process utilizes the remaining ordinary fundamental and the produced SH to generate z-polarized third harmonic (TH). In this way, not only SHG is coupled with SFG process but also the polarization has a strong coupling with the ratio of nonlinear coefficients, resulting in more flexibility in dynamic tuning of the harmonic conversion.

It is noted that the coupled equations have a symmetrical form. We concentrate on the relationship between the maximum TH conversion efficiency 3 maxeK and the ratio of coupling coefficients t, as well as the angle between the incident fundamental polarization and the z-axis of the crystal T. The conversion efficiencies can be solved analytically.

� �22 2 2 2

3 max 2 2

3 cos 1 tan ( 1) 1

(1 )e

t t

t

T TK

�� � �

� and

2 2

3 max 2 2

12 cos(1 )et

tTK

�

The two solutions are valid in different domains, which are separated by a continuous boundary:

2

2

2 2arctan (0 3)1( )

arctan ( 3)1

B

t tttt tt

T

­d d°° � ®

° !° �¯

Domain {0 , 0 ( )}oBt tT Td d f d d is valid for first one and {0 , ( ) 90 }oBt tT Td d f � d is

valid for second one. Generally, the coupled wave equations in nonlinear optics are difficult to solve analytically, especially for the multiple parametric processes. It’s surprising to get such complete analytical results in current configuration. References [1] Zhu, Ding，Zhang, Chao，Qin, Yiqiang. Physical Review E, 86(2), 026602, (2012)

Origin of photovoltaic effect in ferroelectric domain walls — electrostatic potential step vs. local photovoltaic component —

R. Inoue,1,* S. Ishikawa,2 R. Imura,2 Y. Kitanaka,2 T. Oguchi,2

Y. Noguchi,2 and M. Miyayama2 1Dep. of Physics, School of Medicine, Nihon University, Itabashi-ku, Tokyo, Japan

2Dep. of Applied Chemistry, the University of Tokyo, Bunkyo-ku, Tokyo, Japan *Corresponding Author: inoue.ryotaro@nihon-u.ac.jp

The photovoltaic (PV) effect in ferroelectric materials has attracted substantial research

interest because the photoconversion mechanism can be exploited for the development of advanced solar cells. Until now, there has been considerable debate over the mechanism of the PV effects in ferroelectrics in the presence of ferroelastic domain walls (DWs), owing to lack of information on the bulk PV tensor of the host crystals.[1,2] Based on the precise estimation of the bulk PV tensor, we present here the direct evidence that ferroelastic DWs deliver an anomalously large PV response in a Mn-doped barium titanate (Mn-BT). [3]

Figure 1. J–V characteristics of Mn-BT under the visible-light irradiation.

The light (O = 405 nm) was irradiated along the [100] direction of the crystal. Figure 1 shows the current density–voltage (J–V) characteristics of Mn-BT under visible-

light irradiation. In J//[001] configuration, the PV measurements were performed along [001] direction in the single-domain samples. In J//[011] configuration, the PV measurements along [011] direction in the samples where a 90q DWs with a spacing of a15 Pm were introduced by poling. The short-circuit current density (JSC) is found to be reversed by the introduction of the 90q DWs. It is also noteworthy that the photoconductivity is almost the same in both the configurations, which is indicated by almost the same slope of the linear J–V characteristics.

The positive JSC in J//[011] configuration shows the strong light-polarization dependence together with the large positive offset, which cannot be explained only by the electrostatic potential step at the 90q DWs and suggest the local PV component in the DW region.

Our report of the giant PV response in DWs opens a reliable route for enhancing the PV properties in ferroelectrics based on the engineering of domain structure in either bulk or thin-film form.

References [1] S. Y. Yang et al., Nat. Nanotechnology, vol. 5, pp. 143—147 (2010). [2] A. Bhatnagar et al., Nat. Commun., vol. 4, 2835 (2013). [3] R. Inoue et al., Sci. Rep., vol. 5, 14741 (2015).

-4 -2 0 2 4

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Dark 2.5 W/cm2

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rent

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sity

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/cm

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Voltage (V)

(a) J // [001]

Performance Enhancement in Ferroelectric Tunnel Junctions with Active Electrodes and Barriers

D. Wu*

National Laboratory of Solid State Microstructures, College of Engineering and Applied Sciences, and Collaborative Innovation Center of Advanced Microstructures, Nanjing University,

Nanjing 210093, China *Corresponding Author: diwu@nju.edu.cn

Ferroelectric tunnel junctions (FTJs) are composed of two metal electrodes separated by an ultrathin ferroelectric barrier. The reversal of ferroelectric polarization direction varies the potential profile in the tunneling barrier in a nonvolatile manner. This produces a high and a low tunneling resistance state that can be used to represent '0' and '1' for memory applications. It has been reported previously that the on/off ratio can be greatly enhanced in a Pt/BaTiO3/Nb:SrTiO3 device by using an active semiconductor electrode. In this presentation, we report in detail the evolution of transport characteristics as functions of ferroelectric barrier thickness and Nb doping concentration in the electrode, which reveals a ferroelectric control on the additional barrier at the Nb:SrTiO3 surface. Tunneling at the ON state and thermal emission at the OFF state at appropriate Nb concentration and BaTiO3 thickness produce the largest ON/OFF ratio observed. If ferromagnetic metal electrodes are used to construct multiferroic tunnel junctions (MFTJs), the tunneling resistance can be controlled separately by an electrical pulse or a magnetic field to produce four non-volatile states in a single memory cell. We discuss four-state memory functions in MFTJs employing a dielectric/ferroelectric or a ferromagnetic/ferroelectric composite barrier. The composite barrier enhances the asymmetric screening in the two electrodes and increases the ON/OFF ratio. Ferroelectric-controlled spin-filtering through the ferromagnetic/ferroelectric composite barrier enhances both the magnetoresistance and electroresistance.

Elastico-Mechanoluminescence in Non-Piezoelectric CaTiO3:Pr3+ Haifeng Zhao, Xusheng Wang,* Xiaomin Feng, Hua Fang, Yanxia Li, and Xi Yao

Key Laboratory of Advanced Civil Engineering Materials of the Ministry of Education, Functional Materials Research Laboratory, Tongji University, Caoan Road 4800, Shanghai

201804, China *Corresponding Author: xs-wang@tongji.edu.cn

Pure phase orthorhombic CaTiO3:Pr3+ was synthesized by a conventional solid-state method

and its elastico-mechanoluminescence (EML) was characterized. The results revealed that the EML emission peak was centered at 612 nm, similar to its photoluminescence (PL) (Fig.1), indicating both EML and PL originated from 1D2-3H4 transitions of Pr3+. Thermoluminescence and afterglow properties showed tunneling effect in its anomalous fading. The EML mechanism of CaTiO3:Pr3+ was discussed and thought to be attribute to tunneling effect instead of piezoelectricity. Lattice distortion caused by strain diminished the distance between electron captured by trap and Pr4+, and thus increased the probability of immigration of electron to Pr4+, eventually leading to EML.

Figure 1. ML and PL spectra of CaTiO3:Pr

References [1] X. Wang, C-N. Xu, H. Yamada, K. Nishikubo, X-G. Zheng, Adv. Mater., 17, 1254 (2005) [2] J. Zhang, X. Wang, X. Yao, C-N. Xu, H. Yamada, J. Electrochem. Soc., 157, G269 (2010) [3] E. Uzun, Y. Yarar, A. N. Yazici, J. Lumin., 131, 2625 (2011)

Dielectric Responses, Thermally Stimulated Relaxations, and Defect-Property Correlations in Linear Ti-Containing Dielectrics

Jie Zhang, Zhenxing Yue , and Longtu Li State Key Laboratory of New Ceramics and Fine Processing, School of Materials Science and

Engineering, Tsinghua University, Beijing 100084, P. R. China *Corresponding Author: yuezhx@tsinghua.edu.cn

The defect behaviors have being playing a profound role in the performances of functional

dielectrics, besides dielectric response, relaxations, electric breakdown, and etc. And yet, it remains a big challenge to observe and quantify defects, making the defect-property correlations still unclear within dielectrics. Herein, the dielectric responses and relaxation behaviors were systematically investigated upon typically linear Ti-containing dielectrics, such as TiO2, BaTi4O9, and xCa0.8Sr0.2TiO3-(1-x)MgTiO3 ceramics, by means of thermally stimulated depolarization current (TSDC) and dielectric spectroscopy. In addition, the comparisons of defect behaviors were also discussed among these material systems. TSDC characterizations conveyed useful information about the main types of point defects, which were responsible for the dielectric relaxations, and dielectric loss at low and microwave frequencies. The results of TSDC and dielectric-temperature spectra were well consistent, and more importantly it suggested that the TSDC and dielectric spectroscopy are complementary to gain further insight the correlations of defects and properties in dielectric materials.

Fig. 1 The fitted curves of TSDC peaks for TiO2 ceramics

Fig. 2 Dielectric-temperature spectra of xCa0.8Sr0.2TiO3-(1-x)MgTiO3 (x = 0.06, 0.1, 0.2)

Electrocaloric Properties of K(Ta,Nb)O3 Crystals and BaTiO3-based Ceramics H. Maiwa1,*

1Department of Materials and Human environmental Sciences, Shonan Institute of Technology, 1-1-25 Tsujido-Nishikaigan, Fujisawa, Japan

*Corresponding Author: abauthor@uni.edu The electrocaloric effect(ECE) is a phenomenon in which a material shows a reversible

temperature change under an applied electric field. There has been some problem in the conventional refrigerator. Since the conventional refrigerator operates by using a compressor, vibration generation is inevitable. The other disadvantage includes the difficulty in down-scaling. Thermoelectric cooling using the Peltier device has been considered as a solid state cooling device; however, low efficiency has been a hindrance to the wide applications. Although new high-performance materials for thermoelectric cooling are being actively researched, the good results have not been obtained. From the viewpoint of the refrigerator innovation, new refrigerators based on the new mechanism are expected. ECE is considered to be one of the new cooling mechanisms. By using ECE, the application to compact a high energy-effective, inexpensive, and safe refrigerator would be considered. In order to create ECE cooling devices, materials with large ECEs are required. For direct measurement of the ∆T, there are some difficulties. Most temperature changes are less than 1K. And heat dissipation from ferroelectric materials through electrode, wire, and/or the supporting jig for field application occurs. Most probably due to these difficulties, the reports on the direct measurement of ∆T are limited thus far.

In this study, the electrocaloric temperature change, ∆T, due to applied ∆E, of the K(Ta,Nb)O3 crystal and BaTiO3 ceramics is estimated and directly measured. Figure 1 shows the strain-electric field (S-E) loop and temperature-electric field (T-E) loops of the K(Ta,Nb)O3 crystal. The shapes of these loops are similar, suggesting that polarization changes mainly govern both changes. The comparison with the estimations from indirect approach based on Maxwell’s equation will be discussed.

This study is partly supported by grant from KAKENHI #26420684, GRENE(Green Network of Excellence) project from the Ministry of Education, Culture, Sports, Science and Technology.

Figure 1. Strain-electric field (S-E) loop and temperature-electric field (T-E) loops of the

K(Ta,Nb)O3

References [1] M. Valant, Progress in Materials Science, 157, 980 (2012). [2] J. Wang, T. Yang, K. Wei, and X. Yao, Appl. Phys. Lett., , 102: 152907 (2013). [3] H.Maiwa, Jpn J. Appl. Phys., 54, 10NB08 (2015).

Solid solutions PZT doped with nickel and iron ions: the nature of defects and their effects on electrophysical parameters

I. P. Bykov,1,* L. P. Yurchenko,1 L. Jastrabik,2 I. Steinfeldová,3 and M. Boudyš3 1Institute for Problems of Materials Science, National Academy of Sciences of Ukraine,

Krjijanovsky str. 3, Kiev, Ukraine 2Institute of Physics ASCR, v. v. i., Prague, Czech Republic

3Noliac Ceramics s.r.o, Okružní 1144, 500 03 Hradec Králové, Czech Republic *Corresponding Author: ipbykov@gmail.com

PZT material has piezoelectric properties, which appear due to the high dielectric constant,

higher than the electromechanical coupling coefficient, and a significant spontaneous polarization. PZT is prospective material for electro-optic modulators, switches etc

The technology of the ceramic materials production is very complicated and small change in the technology may have a different effect on the synthesis of piezoelectric materials and the chemical reactions in them.

The PZT materials doped with nickel and iron with general chemical formula Pb0.95Sr0.05(Ti0.475Zr0.525)O3 + xNiO + yFe2O3 + zPbO (x = 0, 0.033, 0.066, 0.1, 0.133 wt %; y = 0.1, 0.15 wt %; z = 0.05 wt %) were investigated in the present work. Studies by electron paramagnetic resonance (EPR), electron-microprobe analysis and analysis of electrophysical parameters were used for detection of correlation between intrinsic and impurity defects and electrophysical parameters of the investigated ceramics.

The effect of doping by Fe2O3 and NiO on structural and electrophysical properties is examined with different concentrations of dopants. We can assume that the partial substitution by Fe3+ and Ni3+ at A and B positions in perovskite lattice influence on the formation of an additional phases of magnetoplumbite PbNiO3, PbFe12O19. Charge states of these dopants are associated with oxygen vacancies. The observed EPR lines correspond to the following g-factors: g(Fe3+

ax) ~ 5.9, g(Fe3+rhom) ~ 4.3, g(Ni3+) ~ 2.3 (see Fig. 1). Ni3 + EPR signal is observed

for the first time.

1000 2000 3000 4000 5000 6000

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0.100 wt% NiO

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nsity

, arb

. u.

Magnetic field, Gs

0.033 wt% NiO

Fe3+ax

Ni3+

Figure 1. EPR spectra of Pb0.95Sr0.05(Ti0.475Zr0.525)O3 + xNiO + 0.1 wt %Fe2O3 + 0.05 wt %PbO.

Input: Dynamics of lines intensity changes with NiO concentration increase The EPR signal corresponding to the magnetoplumbite phase (g ~ 2.0) was also observed.

The form of this line points to ferromagnetic behavior. All observed EPR lines depend on the oxygen vacancies concentration.

0,00 0,03 0,06 0,09 0,12 0,15

525

30

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. u.

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Domain Structure and Switching Behavior in Lead-free Epitaxial 0.94(Na0.5Bi0.5)TiO3–0.06BaTiO3 Thin Films with Piezoresponse Force

Microscope Jinyan Zhao,1 Wei Ren,1,* Ming Liu,1, Zuo-Guang Ye,1,2, Lingyan Wang,1 Nan Zhang,1

Gang Niu1 and Peng Shi 1 1 Electronic Materials Research Laboratory, Key Laboratory of the Ministry of Education & International Center for Dielectric Research, Xi’an Jiaotong University, Xi’an 710049, China 2 Department of Chemistry and 4D LABS, Simon Fraser University, Burnaby, British ColumbiaV5A 1S6, Canada

*Corresponding Author: Email: wren@mail.xjtu.edu.cn As a promising lead-free solid solution around the morphotropic phase boundary

composition, epitaxial 0.94(Na0.5Bi0.5)TiO3–0.06BaTiO3 (BNBT6) thin films deposited on Nb:SrTiO3 single crystalline substrates with three orientations (100), (110) and (111) were prepared via a sol-gel process. The crystalline phase and domain structure/switching were investigated. All the films exhibited a perovskite single-phase structure with enhanced peak intensity in accordance with the orientations of single crystalline SrTiO3 substrates. However, since the tensile stress derived from the mismatch between substrate and films, the lattice parameters of films changed. The elongated a-axis length (in-plane lattice parameter) (a=0.3905 nm) and the reduced c-axis length (out-of-plane lattice parameter) (c=0.3894 nm) were obtained in the (100)-oriented BNBT6 films. With the piezoresponse force microscope (PFM), the upward and downward polarized nano-regions in (100) BNBT6 thin films were observed, because its out-of-plane PFM response shows a strong and clear contrast. However, for the (110)- and (111)-oriented films, no obvious contrast appeared in their out-of-plane PFM images, indicating a self-polarization with the polarization points dominantly upward in both the films. In addition, it can be concluded that the non-180o domains existed in all the films with three orientations, as the in-plane PFM phase images show the randomly polarized domains. Domain switching for all the films can be realized, but it is more difficult for the (110)-oriented film to completely switch. A orientation dependence of piezoelectric response for the BNBT6 films was observed, which shows an order of (100) > (110) > (111).

Sandwich-Structure Modulated Poly(vinylidene fluoride) Polymer with Enhanced Energy Density and Discharged Efficiency via Adding Polyacrylate Elastomers

Interlayer J. Chen,1,* Y.F. Wang,1 and H. Wang1

1 State Key Laboratory for Mechanical Behavior of Materials, Xi’an Jiaotong University, No.28, Xianning West Road, Xi'an, China

*Corresponding Author: chenjie203@stu.xjtu.edu.cn

High energy density capacitors are crucial in modern electronic and electrical power

systems. Poly(vinylidene fluoride) polymers are being considered as potential materials for capacitive energy storage systems requiring high breakdown strength, large maximal polarization and fast charge–discharge capability, while are limited in storage energy density by the low discharged efficiency. Polyacrylate elastomers show enhanced maximum polarization and stable remnant polarization with variation of the applied electric field, as a result of its large elastic deformation.

In this study, a sort of sandwich-structured poly (vinylidene fluoride) (PVDF) polymers were prepared by solution casting method combined with electrospinning, in which the polyacrylate elastomers (AR71) films or fibers were introduced between two adjacent PVDF layers as the interlayer. As a consequence, this original sandwich-structured composites displayed 15.7J/cm3 in energy storage density with the breakdown strength of 400MV/m and discharged efficiency increased 10% than that of the pure PVDF films. These results demonstrated that the sandwich-structured PVDF films with polyacrylate elastomers fibers provide a novel approach for developing PVDF films with high energy density and discharged efficiency.

Figure 1. Electric field dependent energy density and discharge efficiency of sandwich

DE/PVDF film, DE Fibers/PVDF film, and pure PVDF. References [1] B. Chu, et al., Science, 313, 334 (2006) [2] K. Yu, et al., Appl. Phys. Lett. 104, 082904 (2014) [3] Y. Wang et al., Adv. Mater., 27, 6658 (2015)

Fundamental Understanding of Ferroelectricity in HfO2-based Ferroelectrics Hiroshi Funakubo1,2,3*, Takao Shimizu2, Kiliha Katayama3, Takanori Kiguchi4, Akihiro

Akama4, Toyohiko J Konno4, and Osami Sakata5 1 School of Materials and Chemical Technology, Tokyo Institute of Technology,

4259 Nagatsuta, Midori, Yokohama 226-8502, Japan 2 Materials Research Center for Element Strategy, Tokyo Institute of Technology, 4259

Nagatsuta, Midori, Yokohama 226-8503, Japan 3Interdisciplinary Graduate School of Science and Engineering, Tokyo Institute of Technology,

4259 Nagatsuta, Midori, Yokohama 226-8502, Japan

4Institute for Materials Research, Tohoku University,

2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan 5Synchrotron X-ray Station at SPring-8, National Institute for Materials Science,

1-1-1 Koto, Sayo, Hyogo 679-5148, Japan *Corresponding Author: funakubo.h.aa@m.titech.ac.jp

The discovery of ferroelectric behavior in HfO2-based thin films1 has triggered intensive

research efforts for the realization of high performance ferroelectric field effect transistors (FeFETs) and high density ferroelectric random access memories (FeRAMs). Compared to the conventional ferroelectrics such as lead zirconate titanate or strontium bismuth tantalate, which have poor interface properties with silicon and are facing severe scaling limitations, HfO2-based ferroelectric thin films have excellent compatibility with complementary metal oxide semiconductor (CMOS) technology. In addition, these films show a stable ferroelectricity down to the thickness of only 5 nm, presenting its potential for scaling down.

In contrast to these extensive application-oriented studies, fundamental nature of ferroelectric HfO2 thin films including its crystal structure, spontaneous polarization and domain structure has not been still elucidated sufficiently. This is due to the polycrystalline characteristics of the deposited films as well as the presence of multiple phases of the previously reported films. In my presentation, we show the first success of the epitaxial growth of HfO2-based films (see Fig.1) and their fundamental properties, such as Curie temperature and spontaneous polarization. Moreover, orientation-controlled film growth was demonstrated even on Si substrates using same buffer layers.

This work was partially funded by the Ministry of Education, Culture, Sports, Science and Technology of Japan (MEXT)

Elements Strategy Initiative to Form Core Research Center, JSPS KAKENHI Grant Numbers 25889024, and MEXT KAKENHI Grant Number 26106509 and 16H00882. Part of this work was also supported by the Center for Integrated Nanotechnology Support at Tohoku University and by the Nanotechnology Network Project of MEXT. The synchrotron radiation experiments were performed at the BL15XU with the approval of NIMS (Proposal Nos. 2014B4704, 2014B4705, 2014A4702). References: [1] T.S. Böscke, J. Müller, D. Bräuhaus, U. Schröder, and U. Böttger, Appl. Phys. Lett. 99,

102903 (2011). [2] T. Shimizu, K. Katayama, T. Kiguchi, A. Akama, T. Konno, and H. Funakubo, Appl. Phys.

Lett., 107, 032910-１-５ (2015).

Fig.1 ABF-STEM image observed for 0.07YO1.5-HfO2 epitaxial film and simulated ABF-STEM images for polar Pca21.

Bismuth Zinc Niobate Thin Film Multilayer Capacitors Fabricated at Low Temperature by Radio Frequency Magnetron Sputtering

Fan He, Wei Ren*, M. Saeed Khan and Peng Shi Electronic Materials Research Laboratory, Key Laboratory of the Ministry of Education &

International Center for Dielectric Research, Xi'an Jiaotong University, No. 28 West Xianning Road, Xi’an, China

*Corresponding Author: wren@mail.xjtu.edu.cn

Thin film multilayer capacitors (MLCs) composed of amorphous Bi1.5Zn1.0Nb1.5O7 (BZN)

dielectric layers with Pt and Cu internal electrodes were fabricated by radio-frequency magnetron sputtering at a temperature below 150 °C. Both BZN thin films and Pt or Cu internal electrodes were deposited in-situ through a set of steel shadow masks at room temperature and post-annealed at 150 °C. The BZN dielectric layers used in the MLCs are amorphous in nature and the thickness for each BZN layer is approximately 220 nm. Metallic Pt or Cu layer used as the internal electrode is about 50 nm thick. Auger electron spectroscopy analysis indicates that there are no diffusion between BZN films and Cu electrodes, as well as no oxidation of Cu electrodes during the fabrication process owing to room-temperature deposition and low-temperature post annealing (150 °C). The thin film MLCs with different number of BZN layers were fabricated. The thin film MLCs with 5 BZN layers and Cu internal electrodes exhibit promising properties with dielectric constant of 72, capacitance density of 1600 nF/cm2, and dielectric loss of 5.4 % at 10 kHz. The results suggest that the BZN thin film MLCs have potential applications on the embedded PCBs.

Effect of Annealing on Piezoelectric Properties of Barium Titanate Piezoelectric Ceramics

Gopal Prasad Khanal,1 Sangwook Kim,1 Shintaro Ueno,1 and Satoshi Wada1,* 1Interdisciplinary Graduate School of Medicine and Engineering, University of Yamanashi,

4-4-37 Takeda, Kofu, Japan *Corresponding Author: swada@yamanashi.ac.jp

Barium titanate (BT), is the first practically used piezoelectric ceramics and is still extensively used in multilayer ceramics capacitors (MLCCs). Previous reports have shown that the physical and electrical properties of BT ceramics frequently depend on morphology and composition of raw materials, fabrication techniques, thermal history and etc1). One of the way to improve electrical properties is to optimize the preparation techniques. Cao et al. has pointed out a necessity to keep thermal and mechanical stress to a value as minimum as possible during the samples’ preparation and processing2). In this study, we investigated an influence of post-annealing on electrical properties of the sintered BT ceramics. BT ceramics were prepared from hydrothermally synthesized BT nanoparticles (Sakai Chemical Industry) by a two-step sintering method with a little modification on a scheme proposed by Karaki et al.3). After 1-min-keeping at 1260 oC, the temperature was rapidly decreased 1150 oC at a rate of 30 oC/min and then kept for 15 hours. The sintered BT ceramics were polished and cut into plate and bar-type samples and then post-annealing was carried out in air at different temperatures, 800–1200 oC for 4 hours. The crystal structures and microstructures of these BT ceramics were investigated by X-ray diffractometer and scanning electron microscopy, respectively. The dielectric, ferroelectric, and piezoelectric properties were investigated for BT samples without and with annealing.

5.0 5.5 6.0 6.5 7.0

240

280

320

360

400A12

A10

A8

d 33 (

pC/N

)

Grain size (Pm)

d33 resonance methodWA

Figure 1. The d33 for samples without and with annealing at different temperatures as a

function of grain size for respective conditions. Figure 1. shows the d33 values for BT samples before and after heat treatment with their average grain size. The abbreviated terms WA represents samples before heat treatment i.e without annealing, whereas A8, A10, and A12 in the plot respectively represent samples annealed at 800 oC, 1000 oC, and 1200 oC in air for 4 hours. The significant increase in piezoelectric properties has been observed after 1000 oC heat treatment. However, the enhancement after 1200 oC heat treatment seems to be saturated. Grain size effect might be dominant in this case. The detail electrical properties will be discussed in the presentation time. References [1] B. Jaffe, WR. Cook, H. Jaffe, London: Academic Press, 53-114 (1971) [2] W. Cao, C.A Randall, J. Phys. Chem Solids, 57, 1499-1505 (1966) [3] T. Karaki, K. Yan, T. Miyamoto, and M. Adachi: Jpn. J. Appl. Phys. 46, L97-L98 (2007)

The heat treatment effect on electrical and structural properties of BiFeO3-BaTiO3 lead-free ceramics

Sangwook Kim,1 Gopal Prasad Khanal,1 and Satoshi Wada1,* 1Interdisciplinary Graduate School of Medicine and Engineering, University of Yamanashi,

Takeda 4-4-37, Kofu, Japan *Corresponding Author: swada@yamanashi.ac.jp

Piezoelectric ceramics are important materials that are widely used for piezoelectric devices,

such as actuators, sensors, and transducers. The piezoelectric devices are used with lead-based piezoelectric ceramics, because of their high piezoelectric property. However, the toxicity of lead and its high vapor pressure have led to a demand for alternative lead-free piezoelectric materials that are environmentally benign from the viewpoint of sustainable development.

Recently, the BiFeO3-BaTiO3 lead-free ceramics is kind to replacement of lead-free piezoelectric ceramics, because of their high curie temperature [1]. M. M. Kumar et al. reported that the (1-x)BiFeO3-xBaTiO3 solid solutions ceramics were observed in the complete compositional range with rhombohedral (BiFeO3-rich, x = 0.00 ~ 0.33), cubic (intermediate, x = 0.33 ~ 0.92), and tetragonal (BaTiO3-rich, x = 0.92 ~ 1.00) structures [2]. On the other hand, R. E. Eitel et al. reported that crystal structure was changed from rhombohedral to pseudo-cubic (polar) structure at 0.75BiFeO3-0.25BaTiO3 composition [3]. The information of phase transition composition is unclear in BiFeO3-BaTiO3 system.

Figure 1. The ferroelectric property of 0.80BiFeO3-0.20BaTiO3 lead-free ceramics with as-

sintering, annealing, and quenching.

In this study, (1-x)BiFeO3-xBaTiO3 (x = 0.20, 0.25, 0.30, 0.33, 0.35, 0.40) lead-free piezoelectric ceramics were fabricated with solid state reaction method. In order to studied effect of heat treatment, the (1-x)BiFeO3-xBaTiO3 ceramics were prepared with as-sintering, annealing, and quenching process. The structures were investigated with x-ray diffraction and Rietveld method. The ferroelectric properties of 0.80BiFeO3-0.20BaTiO3 lead-free ceramics were enhanced with quenching process compare to as-sintered sample. The electrical imprint was observed in as-sintered sample. However, the electrical imprint effect was disappeared with annealing and quenching process. The piezoelectric property was investigated from S-E (strain-electric field) hysteresis loop. The d33

* of 0.80BiFeO3-0.20BaTiO3 ceramics is increased from 123 pm/V (as-sintered) to 173 pm/V (quenched). More detailed properties will be discussed in presentation.

References [1] H. Yang et al., Materials Research Bulletin, 47, 4233-4239 (2012) [2] M. M. Kumar et al., Journal of applied physics, 87, 855 (2000) [3] R. E. Eitel et al., Journal of American Ceramic Society, 92, 2957 (2009)

Mechanistic insight into varistor piezotronics using doped ZnO bicrystals

P. Keil,* N. Novak, T. Frömling,

and J. Rödel

Institute of Materials Science, Technische Universität Darmstadt, Alarich-Weiss-Straße 2,

Darmstadt, Germany *Corresponding Author: keil@ceramics.tu-darmstadt.de

Material systems showing a reversible change of conductivity under mechanical stress are

essential for applications like strain gauges or mechanically triggered transistors. Utilizing the

interaction of piezoelectric charges and the band structure of a semiconductor can lead to

mechanically tunable electrical devices with superior properties. In literature this effect is

referred to as the piezotronic effect.1 For example, ZnO-based varistor ceramics show a

tremendous increase in conductivity when mechanically stressed. This is related to an interaction

of strain induced piezoelectric charges and the electronic structure at the grain boundaries of the

polycrystalline ceramic.2 The type and amount of piezoelectric charges is determined by the

relative orientation of the adjacent grains, whereas the electronic structure is defined by the

defect chemistry at the grain boundary. By preparing doped ZnO bicrystals it is possible to

control both, the orientation as well as the chemistry of the interface. Defined interfaces are

prepared by joining two zinc oxide single crystals in the desired orientation via diffusion

bonding. The defect chemistry at the boundary can be controlled by introducing a thin dopant

layer prior to the joining process. In our work we present a preparation process of ZnO-

bicrystals with controlled orientation and defect chemistry to systematically study the piezotronic

effect on single ZnO|ZnO grain boundaries.

Figure 1: Current voltage characteristics of a Cobalt doped bicrystal interface (left) and cross

section of a prepared bicrystal (right)

References

[1] X. Wen et al., Nano Energy, 14, 276-295 (2015)

[2] R. Baraki et al., Applied Physics Letter, 105, 111604 (2014)

Bulk Self-assembled Ferroelectric Domain Structures in RKTP A. Zukauskas,1,* V. Pasiskevicius1 and C. Canalias1

1Department of Applied Physics, KTH - Royal Institute of Technology, Roslagstullsbacken 21, 10691, Stockholm, Sweden

*Corresponding Author: andriusz@kth.se

During the last years, bulk Rb-doped KTiOPO4 (RKTP), has proven to be a superior

ferroelectric material for fabrication of high aspect-ratio domain gratings [1]. A substantially reduced ionic conductivity together with a pronounced domain-velocity anisotropy, makes RKTP the most suitable material for fabrication of bulk sub-µm ferroelectric domain gratings. These structures are probably the only route to obtain quasi-phase matched (QPM) nonlinear optical interactions exploiting counter-propagating photons such as backward second harmonic generation, mirrorless optical parametric oscillators, and amplifiers [2]. Nevertheless, fabrication of sub-µm periodically poled crystals remains challenging, since not only standard photolithography is not suitable, but also means to gain accurate control of the lateral domain growth are required. This adds complexity in instrumentation and processing and limits the reproducibility of the poled structures. Here we demonstrate a simple technique for fabricating quasi-periodic bulk sub-μm ferroelectric domain gratings in RKTP based on self-organized ferroelectric domain formation. One-dimensional ferroelectric domain structures with average periodicities ranging from 500 nm to 700 nm and extending over 1 mm thick crystal, are obtained by etching with subsequent electric field poling using planar electrodes.

In our experiments, the RKTP single domain crystals are chemically treated in a heated KOH/KNO3 water-based solution for a few minutes. This mixture also selectively etches the crystals by attacking the c- face while keeping the c+ face relatively unaffected. Afterwards, the crystals are poled using planar electrodes and short electric-field pulses. Figure 1 shows SEM images of the domain structure on the (a) former c-, and (b) former c+ faces in a representative 1 mm thick crystal. The average inverted domain width along a direction is 225 ± 75 nm, and the average periodicity is 650 ± 200 nm. The self-assembled domain grating extends over the whole poled area (3 x 8 mm2).

Figure 1. Typical self-assembled ferroelectric domain structure on former c- (a), and former

c+ (b) face of RKTP crystal. Our results indicate that the physical mechanisms behind this self-formation behavior are

related to electrostatic domain-domain interaction and to correlated nucleation [3]. Gaining control of the self-formation process promises to open the path to a simple method

to obtain domain gratings with a higher degree of sub-µm periodicity and to realization of novel optical devices that cannot be implemented with currently available materials and structuring technology. References [1] A. Zukauskas, V. Pasiskevicius, C. Canalias, Opt. Express, 21, 1395-1403 (2013) [2] C. Canalias, V. Pasiskevicius, Nature Phot., 1, 459-462 (2007) [3] V.Ya. Shur, J. Mater. Sci., 41, 199-210 (2006)

Local Piezoelectric Properties and Relaxation Behavior of (K,Na)NbO3-based Piezoceramics with Abnormal Grain Growth

Tian-Lu Men,1 Wei Sun,1 Ke Wang,1,* and Jing-Feng Li1 1 State Key Laboratory of New Ceramics and Fine Processing, School of Materials Science and

Engineering, Tsinghua University, Beijing 100084, P. R. China *Corresponding Author: wang-ke@tsinghua.edu.cn

During the past decades, lead-free piezoceramics has been developing rapidly due to the

increasing concern on environmental protection. However, much attention has been paid to macroscopic property enhancement, which is usually conducted through compositional optimization and processing control. It is considered that further understanding on the microscopic level is necessary for further increasing the performance of lead-free piezoceramics. The present study is focused on the local piezoelectric response and relaxation behavior of a CaZrO3-modified (K, Na)NbO3 (KNN) ceramic sample, which is deliberately chosen due to its high macroscopic d33 more than 300 pC/N and typical abnormal grain growth microstructure.[1,2] The experiments were accomplished by the multiple functions of the Piezoresponce Force Microscope (PFM), such as switching spectroscopy and lithography.

Figure 1. PFM images after lithographed on polished surface at 75 V and relaxed for 0, 10, 100, 800 and 1200 min. L, M and S labelled on the image represent areas with different grain size.

As shown in Fig. 1, the different inner parts of one single large grain (around 5 μm) share a

similar relaxation speed, while the parts from adjacent grains could vary widely even they share the same grain boundaries. By contrast, a trend of diffused relaxation behavior is found for small grains (< 1 μm). Moreover, local piezoelectric measurement was performed on different areas, while the results indicate that large grain size could benefit local piezoelectric performance. It is considered that the macroscopic piezoelectric properties of KNN-based lead-free ceramics could be largely improved if homogenously large grain distribution could be obtained.

References [1] K. Wang, F.Z. Yao, W. Jo, D. Gobeljic, V.V. Shvartsman, D.C. Lupascu, J.F. Li, J. Rödel, Advanced Functional Materials, 23, 4079-4086 (2013) [2] F.Z. Yao, K. Wang, W. Jo, K.G. Webber, T.P. Comyn, J.X. Ding, B. Xu, L.Q. Cheng, M.P. Zheng, Y.D. Hou, Advanced Functional Materials, 26, 1217-1224 (2016)

Energy Efficiency of Electrocaloric Cooling: Material and Cooling-System Considerations

M. Vrabelj,1,2* U. Plaznik,3 Z. Kutnjak,1,2 B. Rožič,1,2 S. Drnovšek,1 A. Poredoš,3 A. Kitanovski3 and B. Malič1,2

1Jožef Stefan Institute, Jamova cesta 39, 1000 Ljubljana, Slovenia 2Jožef Stefan international Postgraduate School, Jamova cesta 39, 1000 ljubljana, Slovenia

3Faculty of Mechanical Engineering, University of Ljubljana, Aškerčeva cesta 6, 1000 Ljubljana, Slovenia

*Corresponding Author: marko.vrabelj@ijs.si The electrocaloric (EC) effect is a conversion of electrical energy to heat and may be defined

as an adiabatic temperature change that occurs in a polar material upon application of an external electric field [1]. The possibility to employ the EC materials in solid-state cooling applications has been one of the main driving forces for numerous studies, especially after 2006, when Mischenko et al. [2] reported the giant EC temperature change ΔTEC of 12 °C at 480 kV/cm and 220 °C in PbZr0.95Ti0.05O3 thin films. Surprisingly, the efficiency of EC materials [3], [4] or prototype devices [5-8] has been discussed only in a few studies, although it is of the utmost importance for applications.

In this work, we investigate the energy efficiency of an EC cooling system in view of the effect of the polarization-electric field P-E hysteresis losses of the EC material, and we also take into account the electric-energy recovery and heat regeneration. For the purposes of the analysis, the (1-x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 (PMN-100xPT) with x = 0, 0.1 and 0.35 ceramics were studied. PMN is considered as a prototype relaxor material while the compositions with a large PT content such as PMN-35PT behave as ferroelectrics [9].

In the contribution we show that if no electric energy-recovery and no heat regeneration are performed on the EC cooling system, the energy efficiency of the system (ξ) does not exceed ~4 % of the efficiency of a Carnot heat pump, irrespective the PMN-100xPT composition. However, if realistic 80 % of the available electric energy is recovered, the ξ is 2.4 %, 9.4 % and 15.8 % for the PMN-35PT, PMN-10PT and PMN, respectively. The poor energy-efficiency in the case of PMN-35PT is a consequence of large P-E hysteresis losses originating from the material’s ferroelectric character. In contrast, PMN is a relaxor material with low hysteresis losses, meaning that a high degree of the electric energy can be recovered, and consequently, a high energy-efficiency can be achieved. Furthermore, we show that if both, the electric-energy recovery (80 %) and the heat regeneration are performed, the EC cooling system employing PMN as an EC working body can achieve the ξ as high as 81 %. Therefore, a high degree of the electric-energy recovery, preferably combined with a heat regeneration process, is needed to create the basis for an efficient EC cooling system.

References [1] M. Valant, Prog. Mater. Sci, 57, 980 (2012). [2] A. S. Mischenko et al., Science, 311, 5765, 1270 (2006). [3] E. Defay et al., Advanced Materials, 25, 3337 (2013). [4] X. Moya et al., Nature Physics, 11, 3, 202 (2015). [5] R. I. Epstein et al., J. Appl. Phys., 106, 064509 (2009). [6] H. Gu et al., Appl. Phys. Lett., 105, 162905 (2014). [7] D. Guo et al., Int. J. Heat Mass Transfer, 72, 559 (2014). [8] M. Ožbolt et al. Int. J. Refrig., 37, 16 (2014). [9] R. A. Cowley et al., Advances in Physics, 60, 2, 229 (2011).

Unipolar fatigue resistance of the Ba(Zr0.2Ti0.8)O3–x(Ba0.7Ca0.3)TiO3 system V. Rojas1*, J. Koruza1, E. Patterson1, and J. Rödel1

1 Institute of Materials Science, Technische Universität Darmstadt, Alarich-Weiss-Straße 2, 64287 Darmstadt, Germany.

*Corresponding Author: rojas@ceramics.tu-darmstadt.de The good piezoelectric properties of the Ba(Zr0.2Ti0.8)O3–x(Ba0.7Ca0.3)TiO3 (BZT-xBCT)

system were initially observed by Liu and Ren [1] in 2009, with a d33 of 620 pC/N and a d33* of ~1000 pm/V. Since then the BZT-xBCT system has been considered as a good candidate to substitute lead-based piezoelectrics, such as Pb(Zr,Ti)O3 (PZT) in actuation applications near room temperature [2],[3].

In this study, several BZT-xBCT compositions throughout the phase diagram were prepared and systematically investigated to evaluate electromechanical properties and their stability during unipolar electric-field cycling. Compositions with three different crystallographic structures, i.e., rhombohedral (R), orthorhombic (O), and tetragonal (T), were synthesized by the mixed-oxide route and sintered for 2 h at 1500 °C. The fatigue resistance of the selected compositions was evaluated by cycling the samples with a unipolar electric field at 5 times the coercive field for up to 107 cycles. The sample´s behavior was tracked by comparing characteristic values, such as remanent polarization, strain asymmetry, and internal bias field.

A relatively stable response with a minor drop in the remanent polarization of 6 and 10 % was observed for the tetragonal and rhombohedral composition after 107 cycles, akin to findings in a reference lead-zirconate titanate material (PZT) (figure 1). The orthorhombic composition on the other hand featured a reduction of 17 %. The different strain mechanisms in each composition were found to be responsible for the different fatigue resistance behavior.

Figure 1. Changes in remanent polarization as a function of the number of cycles for the

three investigated BZT-xBCT compositions, compared to PZT from ref. [4].

References [1] W. Liu and X. Ren, Phys. Rev. Lett. 103, 257602 (2009). [2] J. Rödel, K.G. Webber, R. Dittmer, W. Jo, M. Kimura, and D. Damjanovic, J. Eur. Ceram. Soc. 35, 1659 (2015). [3] M. Acosta, N. Novak, W. Jo, and J. Rödel, Acta Mater. 80, 48 (2014). [4] N. Balke, D.C. Lupascu, T. Granzow, and J. Rödel, J. Am. Ceram. Soc. 90, 1081 (2007).

1

Remarkably Enhanced Photocatalytic Activity in Bi1-xBaxFeO3 Prepared by Sol-Gel

Method Chenlan Zhang, Tong Tong, Jianguo Chen, Dengren Jin, and Jinrong Cheng*

School of Materials Science and Engineering, Shanghai University, 200072, Shanghai, China *Corresponding Author: jrcheng@staff.shu.edu.cn

As a typical multiferroic material, BiFeO3 (BFO), has exhibited photocatalytic activities under visible light irradiation, thanks to its suitable band gap (2.2–2.8 eV) and good chemical stability. However, the low photocatalytic activity of BFO hinders its commercialization in photocatalytic field for the degradation of organic pollution. Therefore, an important task is to improve the photocatalytic activity of BFO for practical use.

In this paper, a series of nano particles of Bi1-xBaxFeO3 (for x = 0,0.01,0.03,0.05,0.10) by Ba2+

acceptor-doping at A-site were synthesized by a sol–gel method. XRD analysis confirms that Ba ions enter into the lattice, and TEM image shows that Ba2+ doping refines the grain whose different size in the range of 30-60 nm. Though testing the photocatalytic degradation of methyl orange(MO), the purpose of our study was to explore the impact of Ba ions on the pure phase BFO, involving the content of Ba ions on the microstructure and surface morphology of the BFO photocatalysts, and the final improvement of their photocatalytic efficiency. We found the optimum concentration of Ba2+

doping is x = 0.03. In this condition, Bi1-xBaxFeO3 has the highest visible light degradation ratio (81% after 3 hours), which is much higher than that of pure phase BFO (66% after 3 hours).

The smaller particle size which reduce the probability of recombination by reducing the time of charge carriers’ migration and the formation of Fe4+ or oxygen vacancies should make some influence on enhancement of catalytic efficiency. We also try to make a prediction that Ba2+ serves as an efficient dopant to influence photocatalytic ability through band gap modifications and the change of Fe-O-Fe bond angle by our first-principles calculations.

References [1] V.B. Naik, R. Mahendiran, Solid State Communications, 149, 754-758 (2009) [2] T. Kawae, H. Tsuda, A. Morimoto, Applied Physics Express, 1, 051601 (2008) [3] Huidan Lu, Zhenyu Du, Jixiang Wang et al., Sol-Gel Sci Technol, 76, 50–57 (2015)

Variation of Electrical Properties with Structural Vacancies in Ferroelectric Niobates (Sr0.53Ba0.47)2.5-0.5xNaxNb5O15 Ceramics

Lingling Wei*

Key Laboratory for Macromolecular Science of Shaanxi Province, School of Chemistry and Chemical Engineering, Shaanxi Normal University, Xi’an, P. R. China

*Corresponding Author: weill@snnu.edu.cn

Abstract:(Sr0.53Ba0.47)2.5-0.5xNaxNb5O15 ceramics (SBNN, 0.0 ≤ x ≤ 2.5) were

prepared by the conventional solid-state reaction method. The Na+ concentration varied from 0.0 to 2.5 so that the tetragonal tungsten bronze (TTB) crystal structure was designed to transform from ‘unfilled’ to ‘filled’ and then to ‘stuffed’ type. Apart from the change in the structural type, the effects of Na+ concentration on the phase structure as well as microstructure, ferroelectric and dielectric properties were also investigated. X-ray diffraction analysis revealed that the SBNN ceramics with x ≤ 1.0 crystallized in the tetragonal tungsten bronze structure with space group of P4bm. With further increasing x above 1.0, the broad asymmetrical diffraction peaks near 32o associated with EDX analyses indicated the existence of some amount of secondary NaNbO3-based phase, which could be attributed to the introduction of excessive Na+. The field emission scanning electron microscope (FESEM) measurement results showed that with increasing x, the anisometric pillar-type grains increased in SBNN ceramics, suggesting that the ‘filled’ tungsten bronze structure preferred to the anisometric morphology. It was also found that Na+ concentration had an appreciable influence on the electrical properties of SBNN ceramics. Introducing Na+ in A-sites to decrease the structural vacancies and increase the distortion degree of NbO6 polar unit was beneficial for the electric properties, while the electric properties would be deteriorated at excessive Na+ content due to the existence of secondary NaNbO3-based phase.

References

[1] S. Lanfredi, C. Darie, F.S. Bellucci, C.V. Colin, M.A. L. Nobre, Dalton Trans. 43 10983-10998 (2014). [2] Y. Gagou, Y. Amira, I. Lukyanchuk, D. Mezzane, M. Courty, C. Masquelier, Y I. Yuzyuk, M.E Marssi, J. Appl. Phys. 115, 64104 (2014). [3] Torres-Pardo, R. Jimenez, J.M. González-Calbet, E. Garcla–González, Inorg. Chem. 50 (2011) 12091−12098. [4] K. Lin, Y.C. Rong, H. Wu, Q.Z. Huang, L. You, Y. Ren, L.L. Fan, J. Chen, X. R. Xing, Inorg. Chem. 53, 9174–9180 (2014). [5] P.B. Jamieson, S.C. Abrahams, J.L. Bernstein, J. Chem. Phys. 48, 5048–5057 (1968).

Acoustic Characterization of PMN single crystal at cryogenic temperatures E.P.Smirnova1*, A.V.Sotnikov1, 2, N.V.Zaitseva1, H.Schmidt2 and M.Weihnacht2

1Ioffe Institute, Politekhnicheskaya 26, St. Petertsburg, Russia 2IFW Dresden, SAWLab Saxony, Helmholtztr. 20, Dresden, Germany

*Corresponding Author: esmirnoffa@gmail.com

Lead magnesium niobate PbMg1/3Nb2/3O3 (PMN) is a prototype relaxor ferroelectric with disordering in the B-position of the perovskite lattice ABO3 and is considered as a model object. Acoustic properties of PMN at cryogenic temperatures were investigated very scarce [1], in contrast to numerous studies of these properties in the dielectric relaxation temperature range around Tm – temperatures of the dielectric constants maxima. Ultrasonic wave velocities (and therefore the elastic constants) and their temperature behavior are, along with the basic interest, important for various applications. The study is focused on the temperature evolution of longitudinal VL and shear VS ultrasonic wave velocities propagating along [100] and [110] directions of PMN single crystal as well as on their attenuation. The measurements were performed in an Oxford Instruments continuous-flow cryostat at temperatures between 4.2 K and 360 K using a RITEC Advanced Ultrasonic Measurement System RAM-5000. The unique PMN specific feature is to preserve the cubic average structure Pm3m from paraelectric phase up to low-temperature relaxor phase which includes about 20% of polar nanoregions with rhombohedral structure at cryogenic temperatures [2]. Temperature dependences of the full set of elastic constants for a cubic structure (C11, C44 and C12) along with bulk modulus B and Young modulus Y were obtained from the velocity data set. The results demonstrate deep minima of the elastic constants around the temperature of the dielectric constants maxima Tm, followed by sharp rise with decreasing temperature and final saturation at temperatures below 50 K. The elastic properties of the disordered relaxor ferroelectric PMN at cryogenic temperatures are compared with the elastic properties of disordered polar dielectrics from the langasite family. References [1] M A Carpenter, J F J Bryson, G Catalan, S J Zhang, N J Donnelly, J. Phys.: Condens. Matter, 24, 045902 (2012). [2] N de Mathant, E. Hussont, S. G. Calvarint, J. R. Gavarris, A. W. Hewat, J. Phys.:Condens. Matter, 3, 8159 (1991).

Energy storage performance of AgNbO3-based lead-free anti-ferroelectric ceramics

Lei Zhao, Qing Liu, Jing-Feng Li* State Key Laboratory of New Ceramics and Fine Processing, School of Materials Science and

Engineering, Tsinghua University, Beijing, 100084, China *Corresponding Author: jingfeng@mail.tsinghua.edu.cn

Recent technology development needs high-performance energy storage materials with a

combination of high energy storage density and energy-storage efficiency. Anti-ferroelectric (AFE) ceramics are promising energy storage materials since they have double hysteresis loops with high polarization and small remanent polarization, and so far many studies have been conducted on lead-based ceramics with (Pb,La)(Zr,Sn,Ti)O3 system as a representative. However, due to the growing environmental concerns, lead-free anti-ferroelectric ceramics are highly desired, and AgNbO3 has been focused recently. In this study, pristine and Mn-doped AgNbO3 ceramics were fabricated by conventional solid-state synthesis in O2 atmosphere. AgNbO3 ceramic shows AFE double hysteresis loop as the applied electric field is above 130 kV/cm and better recoverable energy density (Wrec) of 1.59J/cm3 at 140kV/cm. The addition of MnO2 can further increase Wrec more than 2.20J/cm3 at 150kV/cm by reducing the remanent polarization due to the “hardening” effect of MnO2. Consequently, 0.1wt%MnO2-doped AgNbO3 ceramic exhibits excellent energy-storage properties with Wrec=2.50J/cm3 and thermal stability with Wrec=2.50-2.86J/cm3 at 20-180ºC under 150kV/cm at 1Hz.

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Charged domain wall engineering and conduction phenomena in co-doped lithium niobate lamellae

P. W. Turner, A. Kumar, J. M. Gregg

Centre for Nanostructured Media, School of Mathematics and Physics, Queen's University Belfast,

Belfast BT7 1NN, Northern Ireland, United Kingdom

The field of ferroelectrics research witnessed a seismic shift when, towards the end of the last decade,

J. Seidel et al presented their seminal work concerning the phenomenon of room temperature domain

wall conduction (DWC) in rhombohedral BFO thin films [1]. Ever since, great interest has been invested

into exploring the nature of this phenomenon, both for the advancement of our understanding and

for the potential offered by conducting domain walls (DWs) in new forms of functional devices.

Our study focuses on uniaxial ferroelectrics, specifically LiNbO3, whereupon only 180 degree DWs are

allowed by symmetry. Ceramic samples are both doped and made in-house, and single crystal lamellae

are cut from individual grains using Focused Ion Beam (FIB) processing. DWC has been observed

already [2] in LiNbO3, whereupon n-type conductivity can be enhanced by magnesium doping [2],

however p-type LNO remains more elusive. By doping with zirconium, we have been able to control

p-type free carrier aggregation at DWs as suggested in literature [3].

DWC measurements were problematic due to the presence of an amorphous dead layer arising

through the impregnation of the lamella surface with Gallium ions during FIB milling, something that

has been well documented in studies by L. J. McGilly et al [4] and D. M. Evans et al [5]. We have

therefore refined a process whereby the dead layer may be repaired, yielding a pristine crystal surface.

By engineering stable, charged DWs that demonstrate the coexistence of both n and p-type free

carriers, which can also be electrically contacted from the top and bottom surfaces of single crystal

lamellae, we look to explore the prospect of various electronic functional elements contained entirely

within the DW itself.

We prove that the obtained lamellae are not only ferroelectric, but also often possess spontaneously

formed charged DWs. The samples are switchable through the application of biased PFM tip, yielding

engineered DWs that permeate through the lamellae thickness. We believe that the ability to

demonstrate tuneable control over the character of DWC within LNO lamellae provides a tantalizing

new template for the design and manufacture of components for nanoscale in-wall electronics.

Current progress is extremely promising and we look to present up-to-date DWC data within this

study.

[1] J. Seidel et al (2009), Nature Materials, 8, 229 – 234

[2] M. Schroder (2012), Adv. Func. Mat, Vol 22, Issue 18

[3] Zidong, Pei (2011), AIP Advances, 1, 032171

[4] L. J. McGilly et al (2010), Nano Lett 10 (10), pp 4200-4205 [5] D. M. Evans et al (2014), Philosophical Transactions of the Royal Society A

Orientation-dependent electromechanical properties of Mn-doped (Li,Na,K)(Nb,Ta)O3 single crystals

Hairui Liu,1,* Jurij Koruza,1 Philippe Veber,2 Daniel Rytz3 and Mario Maglione2 1Department of Material- and Geoscience, Technische Universität Darmstadt,

Alarich-Weiss-Straße 2, Darmstadt, Germany 2CNRS-ICMCB, UPR 9048, Université Bordeaux,

87 avenue du Dr A. Schweitzer, Pessac, France 3Forschungsinstitut für mineralische und metallische Werkstoffe,

Struthstr. 2, Idar-Oberstein, Germany

*Corresponding Author: liu@ceramics.tu-darmstadt.de

The increasing of piezoelectric properties of ferroelectric materials in the vicinity of morphotropic and polymorphic phase boundaries has been systematically observed and is believed to be related to the anisotropic flattening of the Gibbs free energy surface [1]. Several mechanisms were proposed to explain the property enhancement, i.e., the coexistence of mixed phase at phase boundaries, appearance of nanodomains, and E-field-induced phase transition. In order to reveal the contributions of different mechanisms, detailed orientation-dependent investigations of these materials in single crystalline form are needed. For example, recent work on Na0.5Bi0.5TiO3-BaTiO3 crystals [2] showed a large contribution of E-field-induced phase transition followed by polarization extension along the [001]PC orientation, which resulted in large electromechanical properties at the rhombohedral-tetragonal phase transition. Unfortunately, only limited information is currently available for (Na,K)NbO3-based single crystals, which is one of the most promising alternatives to lead-based piezoelectrics [3]. This is partially related to the difficulty in obtaining high-quality crystals, resulting from the volatilization and segregation phenomena [4].

In this work, we investigated the influence of crystallographic orientations on the temperature-dependent electromechanical properties of Mn-doped (Li,Na,K)(Nb,Ta)O3 (Mn:KNLTN) single crystals, with two different crystallographic orientations, which were grown by the self-flux solution growth method with a Pt-spatula acting as a preferential nucleation site [5]. The crystallographic orientations were determined by Laue backscattering method. The chemical composition was analyzed by combining both electron probe micro analysis and inductively coupled plasma optical emission spectroscopy. The ferroelectric hysteresis and E-field-induced strain curves were measured with an aixACCT TF ferroelectric analyzer. Highest maximum polarization Pmax, coercive field EC and negative strain Sneg were achieved when E was oriented along the polar axis. The origin of orientation-dependent electrical properties was found to be related to the anisotropic polarization rotation and polarization extension. The highest bipolar strain (0.31 %) and large-signal piezoelectric constant d33

* (1391 pm.V-1) were obtained along the [001]PC orientation at the orthorhombic-tetragonal phase transition and were much higher than the values obtained along the [110]PC orientation. This should be associated with E-induced phase transition and polarization extension.

References [1] A. A. Heitmann, and G. A. Rossetti. J. Am. Ceram. Soc., 97, 1661 (2014) [2] W. Ge et al., J. Appl. Phys., 111, 093508 (2012) [3] Y. Saito et al., Nature, 432, 84 (2004). [4] H. Liu et al., CrystEngComm, 18, 2081 (2016). [5] P. Prakasam et al., C. R. Phys., 14, 133 (2013).