39R.Arivuselvi et al. / International Journal of Science, Technology and Humanities 1 (2014) 39 - 43

Synthesis, growth, structural, optical, spectral and dielectric studies of Barium Tetra Borate (BTB) single crystal

R. Arivuselvi , A. Ruban Kumar*

School of Advanced Sciences, VIT University, Vellore, India - 632014.Received: 8 September 2014: Received in revised form 8 October 2014; Accepted 15 October 2014

AbstractThe non linear optical barium tetra borate crystal was grown by slow solvent evaporation solution technique. Powder X-ray diffraction analysis was used to find out the lattice parameters. The various functional groups in the grown crystal were identified and assigned using FTIR spectroscopy. The cut-off wavelength, optical transmission and band gap energy of grown crystal were determined from UV-Visible spectral analysis. Second harmonic generation of title compound has been measured by Kurtz and Perry powder technique. The photoluminescence study is also analysed. The dielectric constant and dielectric loss of the BTB crystal was calculated at different temperatures and frequencies to analyse the electrical properties.

Keywords: Powder X-ray diffraction; FTIR spectroscopy; UV-Visible studies; Kurtz and Perry technique.

© 2014 Sri Vidya Mandir Arts & Science College, Uthangarai

1. IntroductionThe design and synthesis of new materials with

large macroscopic non linearities has been recording more and more attention. Especially research in borate crystals has been conducted for the past few decades and it remains strong to this date due to their promising physical properties such as their interesting non linear optical, transparency to a wide range of wavelength, high laser damage tolerance, piezoelectric, luminescent and other useful properties for technical applications [1-4]. The barium based borate single crystal has low acceptance angle, and high optical nonlinearity. It

permits deep UV generation and has great potential for generating tunable visible and IR light as an optical parametric amplifier [5].

In the present investigation the growth of Barium Tetra Borate crystal was reported by the low temperature solution growth method. The grown crystal was subjected various characterizations such as powder X-ray diffraction analysis, Fourier transform infrared analysis, optical absorption and transmission studies, photoluminescence studies, non linear optical test and dielectric studies. The results are discussed in detail.

*Corresponding author.Tel:+91 9443107659. E-mail address:arubankumar@vit.ac.in© 2014Sri Vidya Mandir Arts & Science College, Uthangarai

International Journal of Science, Technology and Humanities 1 (2014) 39-43

Available online at www.svmcugi.com

International Journal of Science, Technology and Humanities

40 R.Arivuselvi et al. / International Journal of Science, Technology and Humanities 1 (2014) 39 - 43

2. Experimental ProcedureThe starting materials (Analar grade) for the

growth of title compound were prepared according to the following reactions,

BaCl2.2H2O+ 4H3BO3→BaB4O7 + 2HCl+7H2O

The 12.21 gm of barium chloride dihydrate and 12.3 gm of boric acid were dissolved in 50 ml of double distilled water at 50 °C. Then the resultant solution was stirred until it becomes homogenous solution. The resulting solution was filtered and kept undisturbed condition. After 140 days, a well defined, colourless and transparent crystal of dimensions 17 x 4 x 3 mm3

was obtained using solvent evaporation technique as shown in fig 1.

Fig.1 Photograph of BTB crystal

3. CharacterizationThe X-ray diffraction analyses of the crystal

were carried out using SHIMAZDU XRD – 600 powder X-ray diffractometer. The optical absorption and transmission were recorded in the wavelength range 200 – 1100 nm using Lamda 35 UV-Visible spectrometer. The functional groups were studied using SHIMAZDU Fourier transform infrared spectrometer within range 400 – 4000 cm-1. The photoluminescence spectrum of BTB crystal was recorded using HORIBA JOBINYVON SLUORO LOG 3 spectrophotometer. The NLO conversion efficiency grown crystal was measured by Kurtz and Perry powder SHG test using a Q – switched Nd : YAG laser with the first harmonic output at 1064 nm. Dielectric properties are correlated with the electro optic property of the crystals. The dielectric responses of the samples were studied by LCR HIOKI 3532 HI TESTER from the frequency range 50 Hz to 5 MHz in the temperature range 313 K to 343 K.

4. Result and Discussion4.1 Powder XRD analysis

The grown crystals were subjected to powder X-ray diffraction. The diffraction pattern was recorded between 100 and 800 using Shimazdu XRD -600 powder X-ray diffractometer as shown in fig.2 employing monochromated CuKα radiation (λ= 1.5418 Å) at a scan speed of 10/min. It is observed that the BTB crystal belongs to orthorhombic crystal system with a space group Pmmn. The lattice parameter values are a = 13.930 Å, b = 12.120 Å and c = 7.116 Å.

Fig.2 Powder X-ray diffraction Pattern of BTB

4.2 UV-Visible assessmentsThe UV-Visible absorption and transmittance

spectrum was recorded by the instrument Lamda 35 UV-Visible Spectrometer in the range of wavelength from 200 nm-1100 nm. The recorded absorption and transmittance UV-Visible spectrum of Barium Tetra Borate crystal are shown in Figures 3 & 4. The cut off wavelength of the grown crystal is 220 nm and its transparency is about 98% in the UV-Visible region. The calculated cut-off wavelength was used to calculate the energy gap (Eg) of BTB crystal by the following relation,

Eg = h c/λ

Where h is the Planck’s constant (6.625 x 10-34

JS-1), c is a velocity of light (3x108 ms-1) and λ is the cut off wavelength of grown crystal. The estimated forbidden energy gap (Eg) is 5.64 eV and this value indicates that the grown crystal belonging to the category of typical insulating material [6]. The calculated band

41R.Arivuselvi et al. / International Journal of Science, Technology and Humanities 1 (2014) 39 - 43

gap value of BTB crystal was lower than that of BBO (6.43eV) and LBO (7.7eV).

Fig.3 UV-Visible absorption spectrum of BTB crystal

4.3 FTIR analysisThe FTIR of BTB crystal was confirmed by Fourier

transform Infrared spectrometer in the range of (4000-400)cm-1 using KBr pellet technique. FTIR spectrum of grown crystal is shown in fig. 5. The broad band at 3218 cm-1 is due to O-H stretching mode of vibration.

Fig.4 UV-Visible transmittance spectrum of BTB crystal

The peak at 2631 cm-1, 2511 cm-1 and 2363 cm-1 are due to overtones and combination OH in-plane bending mode. The vibration modes of borate series crystal are mainly active in three IR spectral regions, the B-O stretching of trigonal B-O in BO3 is occurs between 1500-1200 cm-1 , B-O stretching of trigonal B-O in BO4 is occurs between 1200-850 cm-1 and bending vibrations of various borate series occurs in between 800-650 cm-1[7] .The strong band at 1456 cm-1

is assigned to the B-O stretching of B-O-B bridge [8] The broad band at 1192 cm-1 is due to the asymmetric stretching mode of (BO3)-3 ions. The peak at 881 cm-1 and 809 cm-1 are due to the asymmetric stretching mode of B-O in BO4. The strong band at 547 cm-1 can be assigned to the symmetric stretching mode of B-O in BO4.

4.4 Photoluminescence studyThe photoluminescence studies can be used to

identify the excitation and emission properties of grown crystal [9]. The photoluminescence spectrum of title compound as shown in fig.6 was recorded in the range from 225 – 650 nm at room temperature. A high pressure xenon lamp was used as an excitation source. The BTB crystal was excited at 410 nm, the results indicate that the grown crystal have a violet emission property. Hence the photoluminescence spectrum reveals that electronic property of the grown crystal.

Fig.5 FTIR spectrum of BTB crystal

Fig.6 PL spectrum of grown crystal

42 R.Arivuselvi et al. / International Journal of Science, Technology and Humanities 1 (2014) 39 - 43

4.5 Non linear optical test The Kurtz and Perry powder technique was most

widely used to find out the non linear optical efficiency of the title compound [10]. In this experiment Q-switched pulses were obtained from Nd : YAG laser with the wavelength of 1064 nm. The crystal was ground a particle size of 125 – 150 micro metre packed in a micro capillary of uniform bore and then exposed to laser radiation with 10 ns pulse width. The output from the sample was monochromated to collect the intensity of 532 nm components and the fundamental was eliminated. The second harmonic radiation generated by the randomly oriented microcrystal was focused by a lens and detected by a photomultiplier tube. A strong bright green emission emerging from the sample shows that it exhibits good NLO property [11, 12]. Potassium dihydrogen orthophosphate was used as a reference material, the SHG efficiency of BTB crystal is found to be 0.55 times of KDP.

4.6 Dielectric studiesDielectric studies of the grown BTB crystal

have been carried out at various frequencies and temperatures. The behavior of the crystal under electric field has close relationship with the laser irradiation and hence the dielectric constant and dielectric loss can be studied from the dielectric studies [13].The dielectric constant and dielectric loss were calculated from the equation

εr = ct

ε0A and tan δ = εrD

Where, ε0 is the permittivity of free space (8.854×10-12 F/m), t is the thickness of sample (mm), D is the dissipation factor and A is the area of cross section of the sample (mm). The dielectric constant and dielectric loss with log frequency are plotted in fig.7 and 8.

It is observed from the figures that both dielectric constant and dielectric loss of BTB crystal are high at low frequencies and they decrease with increase in frequency. The very high value of εr at low frequencies may be due to the presence of all the four types of polarisations namely space charge, orientational, ionic and electronic and its low value at higher frequencies

may be due to the loss of significance of these polarisation gradually [14].

At higher frequencies, the measure of dielectric loss is very low since the electric wave frequency is not equal to that of natural frequency of the bounded charge and hence the radiation is weak. The measure of low dielectric loss at various frequencies is also due to dipole rotations. At high frequencies orientation polarisation ceases and hence the energy need not be spent to rotate dipoles [15].

Fig.7 Plot of log frequency with Dielectric Loss at different temperature

Fig.8 Plot of log frequency with Dielectric constant at different temperature

5. ConclusionOptical quality single crystal of Barium Tetra

Borate was grown by slow evaporation solution growth

43R.Arivuselvi et al. / International Journal of Science, Technology and Humanities 1 (2014) 39 - 43

technique with a period of 140 days. The structure of the crystal was confirmed by powder X-ray diffraction, the crystal belongs to orthorhombic crystal system with space group of Pmmn. The UV-Visible study reveals that the grown crystal to be suited on the category of typical insulating materials having the band gap energy 5.64 eV. The functional groups of the compound have been determined from FTIR analysis. The photoluminescence spectrum obtained from the present study implies that the violet emission at 410 nm. The BTB crystal exhibits the second harmonic generation efficiency of about half times that of KDP. The low dielectric loss and dielectric constant at high temperatures of the compound shows that the material is more suitable candidate for NLO applications. Our future research efforts will be devoted to the exploration of new SHG compounds by introduction of other type of alkali metal or alkali earth metal into the borates.

AcknowledgementsThe authors express their gratitude to the

management of Vellore Institute of Technology, Deemed University,Vellore for providing laboratory facilities. The authors thank Dr.M.Basheer Ahamed, School of Science and Humanities, B.S. Abdur Rahman University, Chennai, India for his generous help to carry out NLO test. The authors sincerely acknowledge the Photoluminescence measurement facility extended by the Professor and Head, Department of nanotechnology, Karunya University, Coimbatore, India. The authors would like to thank Dr. Joe Jesudurai, Associate Professor, Department of Physics for provided dielectric instrumentation facility at Loyola College, Chennai, India. One of the authors (R.A) extends the grateful to the management, Dr.K.Arul, Principal and Dr.M.Selvapandiyan, Head, PG and Research Department of Physics, Sir Vidya Mandir Arts and Science College, Uthangarai for their kind support to carry out this work.

References[1] X.Meng, Y.Song, H.Hou, Y.Fan, G.Li, Y.Zhu,

Inorg.Chem 42 (2003) 1306.

[2] S.Wang, E.V. Alekseev, W.Depmeir, T.E. Ibrecht Schmitt, Inorg.Chem 50 (2011) 2079.

[3] G.Paramesh, R.Vaish, K.B.R.varma,J.Non.Cryst.Solids 357 (2011) 1479.

[4] E.R.Shaaban, Physica B 406 (2011) 406.

[5] D,Eimerl, L.Davis, S.Velsko, E.K.Graham and A.Zalkin, J.Appl.Phys. 62 (1987) 1968 .

[6] M. Selvapandiyan, J. Arumugam, P. Sundaramoorthi, S. Sudhakar, J. Alloys Comp. 580 (2013) 270.

[7] K.Prbba, T.Rajeshkumar, Shi Feng Du, M,Vimalan, A.Dayalan, P.Sagayaraj, Mater. Chem. Phy. 121 (2010) 22.

[8] Q.Y Shang, B.S.Hudson, Spectrochim. Acta 47A (1991) 291.

[9] G.Anandha Babu, P.Ramasamy. Current Applied Physics 10 (2010) 214.

[10] D. Jaikumar, S. Kalainathan, G. Bhagavannarayanna, J.Cryst. Growth 312 (2009) 120.

[11] S.K. Kurtz, T.T. Perry, J. Appl.Phys. 39 (1968) 3798.

[12] S. Moitra, T. Kar, Cryst.Res.Technol. 45 (2010) 70.

[13] A. Baskaran, S. Arjunan, C.M. Raghavan, R. Mohankumar, R. Jayavel, J. Cryst. Growth 310 (2008) 4548.

[14] S. Sankar, MR. Manikandan, S.D. Gopal Ram, T. Mahalingam, G. Ravi, J. Cryst. Growth 312 (2010) 2729.

[15] C.M. Raghavan, R. Pradeepkumar, G. Bhagavannarayanna, J. Cryst. Growth 311 (2009) 3174.