Lead-Free Ceramic-Polymer Composites for Embedded Capacitor and Piezoelectric

Applications

P. Kumar*

Department of Physics, National Institute of Technology, Rourkela, Odisha, India, 769008

Correspondence to: P. Kumar (E-mail: pvn77@rediffmail.com, pawankumar@nitrkl.ac.in)

Tel./fax: 0661-2462726

Abstract: Modern composite materials constitute a significant proportion of the engineered

materials market ranging from everyday products to sophisticated niche applications like:

charge storage in capacitors, atomic force microscopy (AFM), medical ultrasound probes,

health monitoring techniques, in civil engineering, in underwater applications such as sonars

submarines, in high frequency and energy harvesting applications, etc. [1,2]. Ferroelectric

ceramics, polymers and their composites form a class of functional materials, that are being

increasingly utilized for their specific dielectric, ferroelectric, piezoelectric, pyroelectric,

electro-optic and electro-chromic as well as superconducting properties in modern electronic

devices [3-5]. Considering the increased rate of utilization of the ceramics polymer

composites, the present work has been undertaken to develop ceramic polymer composites to

study its dielectric & piezoelectric properties.

In this work, lead free (BZT-BCT) & CCTO ceramics were prepared by conventional solid

state reaction route. Using XRD technique, single perovskite phase was confirmed at a

calcination temperature of 1300oC for 4h for the (BZT-BCT) system & 1050

oC for 4h for the

CCTO system. The sintering of the (BZT-BCT) ceramics was carried out at 1300, 1350 and

1400oC for 6h each, respectively. For achieving better density, the sintering of the CCTO

ceramics was carried out at 1050 and 1100oC for 8h each, respectively.

PVDF (Fluka,UK) with a molecular weight ~ 5,30,000 was used for the preparation of the 0-

3 composite thick films of the {0.25(BZT-BCT)-0.75[(1-x)PVDF-xCCTO]}/(BZT-BCT)-

(PVDF-CCTO) system with (x = 0.02, 0.04, 0.06, 0.08 & 0.10). (BZT-BCT)-(PVDF-CCTO)

composite thick films were prepared by hot uniaxial pressing. The stoichiometric proportions

of the volumetric proportions of PVDF and sintered (BZT-BCT) & CCTO powders were hot

pressed at ~150ºC at an applied pressure of ~6.5 MPa for 30 mins and then cooled to room

temperature (RT) under pressure.

Epoxy resin, Araldite-AW-106 and hardener, HV-953-IN were used for the preparation of the

0-3 composite samples of the {0.2(BZT-BCT)-0.8[(1-x)epoxy-xCCTO]}/(BZT-BCT)-

(epoxy-CCTO) system with (x = 0.02, 0.04, 0.06, 0.08 & 0.10). Pin samples of the (BZT-

BCT)-(epoxy-CCTO) composites were prepared by cold pressing and hand lay-up

techniques.

Maximum value of εr~ 4000 and max. piezoelectric coefficient (d33) ~ 281 pC/N at RT were

obtained in the (BZT-BCT) 50/50 ceramics samples. The RT values of r and tan at 1 kHz

frequency of the CCTO ceramic samples sintered at 1100oC are found to be ~ 11,537 and

0.21, respectively. The highest values of εr ~91 at RT and d33 ~19pC/N of the 0.25(BZT-

BCT)-0.75[(1-x)PVDF-xCCTO] composites are obtained for x=0.08. Whereas, the 0.2(BZT-

BCT)-0.8[(1-x)epoxy-xCCTO] composite with x = 0.08 exhibited highest values of the r ~61

and d33 ~15pC/N piezoelectric coefficient. These excellent dielectric and piezoelectric

properties of the studied composites suggested their potential applications in embedded

capacitor and piezoelectric applications.

References:

[1] K. K. Chawla, Composite Materials: Science and Engineering (Third Edition, Springer,

New York, 2012).

[2] V. Y. Topolov and C. R. Bowen, Electromechanical Properties in Composites based on

Ferroelectrics (Springer, London, 2009).

[3] G. Edwards, H. L. W. Chan, A. Batten, K. H. Lam, H. S. Luo and D. A. Scott, Sensors

and Actuators A. 132, (2006) 434.

[4] W. W. Wolny, Journal of the European Ceramic Society. 25, (2005) 1971.

[5] A. J. Moulson and J. M. Herbert, Electroceramics: Materials, Properties, Applications,

Second Edition (John Wiley & Sons Ltd., England, 2003).

by

Dr. Pawan Kumar

Lead Free ceramic-polymer

Composites for embedded capacitor and piezoelectric

applications

Department of Physics

N. I. T. Rourkela

7/3/2015 2

• Introduction • Motivation and Objective • Structural, Dielectric and Piezoelectric properties of

BZT-BCT System • Structural, Dielectric and Piezoelectric properties of

(BZT-BCT)-PVDF and (BZT-BCT)-(PVDF-CCTO) composites

• Structural, Dielectric and Piezoelectric properties of (BZT-BCT)-EPOXY and (BZT-BCT)-(EPOXY-CCTO) composites

• Conclusions

Outlines:

3

Aim of the present work:

The present work is divided into four parts: 1. To synthesize & Characterize the lead-free (BZT-BCT) ceramics near

MPB. 2. To synthesize & characterize the high dielectric constant CCTO

ceramics. 3. To prepare the 0-3 ceramic-polymer composites by using the ceramic

powders of the best MPB composition of (BZT-BCT) system as fillers with PVDF and epoxy as the matrices.

4. To further modify the dielectric properties (r > 50 at RT and at 1kHz frequency) of the best (BZT-BCT)/PVDF, (BZT-BCT)/epoxy composites by the addition of CCTO ceramic particles as fillers.

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Part 1 To synthesize & Characterize the lead-free (BZT-BCT) ceramics near MPB and to suggest the best MPB composition

7/3/2015 5

Comparison between properties of

lead and lead free materials

Materials εr tanδ d33 (pC/N)

Tc (°C)

PZT 3400 0.02 590 190

PMN-PT 5569 0.003 1720 -

NKN 290 0.04 80 420

BNBT 665 0.02 125 120

BZT-BCT 3060 0.02 300 93

6

Materials and method of preparation of (BZT-BCT)

ceramics :

x[Ba(Zr0.2Ti0.8)O3]-(1-x)[(Ba0.7Ca0.3)TiO3]

(for x = 0.48, 0.50 & 0.52)/(BZT-BCT)

BaCO3, CaCO3, ZrO2, TiO2

Ball milled for 8 h in acetone

TG-DSC

Calcination at 1100, 1200 &

1300 oC for 4 h

Green pellets

Sintering at 1300, 1350 & 1400 oC for 6 h

7

XRD of the sintered (BZT-BCT) ceramic samples:

20 30 40 50 60 70

Inte

ns

ity

(a

.u.)

2(in degrees)

1300 oC for 6 h

1350 oC for 6 h

1400 0C for 6 h

(00

1)

(10

1)

(11

1)

(00

2)

(20

0)

(10

2)

(21

1)

(a)

20 30 40 50 60 70

Inte

ns

ity

(a

.u.)

2(in degrees)

1300 oC for 6 h

1350 oC for 6 h

1400 oC for 6 h

(b)

(10

0)

(10

1)

(11

1) (2

00

)

(10

2)

(11

2)

(22

0)

20 30 40 50 60 70

Inte

ns

ity

(a

. u

.)

2indegrees

1300 oC for 6 h

1350 oC for 6 h

1400 oC for 6 h

(c)

(00

1)

(10

1)

(11

1)

(00

2)

(20

0)

(10

2)

(21

1)

*

* Secondary Phase

(a) 48-52

(b) 50-50

(c) 52-48

8

20 30 40 50 60 70

4 5 .0 4 5 .5 4 6 .0

Inte

ns

ity

(a

.u.)

2 (d e g re e s )

In

ten

sit

y (

a.u

.)

2(degrees)

1300 oC for 6 h

1350 oC for 6 h

1400 oC for 6 h

(10

0)

(10

1)

(11

1)

(20

0)

(10

2)

(11

2)

(22

0)

XRD of the (50BZT-50BCT) ceramic samples:

9

Summary of lattice parameters of (BZT-BCT) ceramic

samples:

Compositions of

( BZT-BCT)

system

Structure Lattice

parameters (Å)

Volume (Å3)

48-52 tetragonal a = 3.991

b = 3.991

c = 4.016

V = 63.97

50-50 tetragonal a = 3.996

c = 4.017

V = 64.16

monoclinic a = 5.645

b = 4.015

c = 3.994

V = 64.13

52-48 Tetragonal a = b = 4.005

c = 4.008

V = 64.28

10

Dielectric properties of (BZT-BCT) ceramic samples

with frequency (sintered at 1400oC):

2 3 4 5 6

0.0

0.2

0.4

0.6

0.8

1.0

1.2

tan

Frequency (log10 Hz)

48BZT-52BCT

50BZT-50BCT

52BZT-48BCT

2 3 4 5 6

2000

2500

3000

3500

4000

r

Frequency (log10 Hz)

48-52

50-50

52-48

11

Summary of Dielectric properties of (BZT-BCT)

ceramic system:

Samples Dielectric parameters Tc in oC

r at Tc

r tan

48-52-1300 1432 0.0069 115 3449 1.9

48-52-1350 2082 0.0075 115 3769 1.9

48-52-1400 2038 0.0102 115 3958 1.9

50-50-1300 3367 0.0089 108 4962 1.7

50-50-1350 3176 0.0090 108 5162 1.8

50-50-1400 3888 0.0143 108 5529 1.8

52-48-1300 1396 0.0094 96 4070 2.0

52-48-1350 2652 0.0110 96 4541 2.0

52-48-1400 2463 0.0130 96 4962 1.9

12

Summary of Ferroelectric & Piezoelectric properties of

(BZT-BCT) ceramic system:

Compositions

of (BZT-BCT)

system

Sintering

temperature

in oC

Pr value in

µC/cm2

Ec value in

kV/cm

d33 values

in pC/N

48-52 1300 0.016 1.339 208

1350 1.602 1.836 215

1400 2.959 1.922 270

50-50 1300 2.344 1.772 224

1350 2.013 1.967 258

1400 1.781 1.530 281

52-48 1300 1.629 1.896 170

1350 1.659 1.323 178

1400 1.926 1.327 186

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Part II To Synthesize & Characterize the Lead-Free Dielectric Constant CCTO Ceramics

14

Summary of RD, Average grain size & Dielectric

properties of CCTO ceramic system:

Sintering

temperature

of CCTO

ceramics in oC

RD % Average grain

size in µm

Dielectric

parameters at RT

at 1 kHz

r

tan

1050 91.93 10.3 11498 0.1880

1100 94.67 12.1 11537

0.2137

15

Comparison between properties of

polymers

Polymers εr at 1

kHz

tan at

1 kHz

Tg in

°C

Tm in

°C

d33

(pC/N)

Poly

vinylidene

fluoride(PVDF)

8.4

0.019 - 35 220 6-7

Poly vinyl

chloride(PVC)

3.3 0.017 82 100-

260

0.5-1.3

Poly carbonate

(PC)

2.99 0.0015 150 225 -

Epoxy 3.2 - 145 - -

polyimide 3.5(1

MHz)

- >400 - -

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Part III To prepare the (BZT-BCT)-PVDF 0-3

ceramic-polymer composites To further modify the dielectric

properties of the best (BZT-BCT)/PVDF, composites by the addition of CCTO ceramic particles as fillers

17

Materials and method of preparation of (BZT-

BCT)-PVDF composites :

• PVDF (Fluka) and sintered (BZT-BCT) powders.

• Volume % (BZT-BCT) (5 – 25 %).

• Dry magnetic stirring for 1 hour.

• Ultrasonification for 30 mins.

• Hot uniaxial pressing of the well mixed powder at

150°C and at an applied pressure of ~ 6.5 MPa for 30

min and then cooled to RT holding the pressure.

• Flexible, thick and self standing films were obtained.

18

Summary of dielectric parameters & d33 of (BZT-

BCT)-PVDF composite systems with different vol% of

ceramics :

Materials Vol% of

ceramics

Parameters

r at RT at

1 kHz

tan at

RT at 1

kHz

rmax at 1

kHz

Tmax at 1

kHz

d33 in

pC/N

(BZT-BCT)-(1-

) PVDF

composites

= 0.05 20 0.049 21 118 8

= 0.10 23 0.041 24 112 9

= 0.15 25 0.035 27.5 112 15

= 0.20 31 0.026 33 116 29

= 0.25 42 0.018 44 97 31

19

Summary of dielectric parameters & d33 of (BZT-

BCT)-(PVDF-CCTO) composite systems with different

vol. fractions of ceramics :

Materials Vol% of

ceramics

Parameters

r at RT at

1 kHz

tan at

RT at 1

kHz

rmax at 1

kHz

Tmax at 1

kHz

d33 in

pC/N

0.25(BZT-BCT)-

0.75[(1-x)PVDF-

xCCTO]

composites

x = 0.02 47 0.089 - - 7

x = 0.04 59 0.026 - - 8

x = 0.06 77 0.017 - - 13

x = 0.08 90 0.013 - - 19

x = 0.10 66 0.009 - - 10

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Part IV To prepare the (BZT-BCT)-Epoxy 0-3

ceramic-polymer composites To further modify the dielectric

properties of the best (BZT-BCT)/Epoxy, composites by the addition of CCTO ceramic particles as fillers

21

Materials and method of preparation of BZT-BCT.

Epoxy composites :

In the present work the following series of 0-3 ceramic polymer

composites using epoxy as polymer matrix were prepared by cold

pressing and hand lay up technique.

• [0.5[Ba(Zr0.2Ti0.8)O3]-0.5[(Ba0.7Ca0.3)TiO3]]-

epoxy/(BZT-BCT)-(1-)epoxy composites, where,

= 0.05, 0.10, 0.15, 0.20 and 0.25 volume

fractions.

22

For the preparation of the composites, sintered

ceramic powders were mixed with epoxy resin and

hardener (in the weight ratio of 15:1) in required

volume fractions.

The mixture of sintered (BZT-BCT) powder and

epoxy resin was poured into the cylindrical cavity of

the mould used and the two halves of the mould

were fixed properly.

It required proper care during the fixing of moulds,

as some of the resins may squeeze out.

After closing the mould properly, the specimens

were allowed to solidify inside the moulds at RT for

24 h.

23

The steel mould was used for the

preparation of cylindrical (pin) type

specimen of length ~ 35 mm and

diameter of ~ 10 mm.

24

Summary of dielectric parameters & d33 of (BZT-

BCT)-epoxy composite systems with different vol% of

ceramics :

Materials Vol% of

ceramics

Parameters

r at RT at

1 kHz

tan at

RT at 1

kHz

rmax at 1

kHz

Tmax at 1

kHz

d33 in

pC/N

(BZT-BCT)-(1-

) epoxy

composites

= 0.05 14 0.15 18.62 123 6

= 0.10 20 0.11 24.16 133 8

= 0.15 22 0.07 29.07 148 11

= 0.20 34 0.01 44.97 142 16

= 0.25 25 0.05 29.34 150 9

25

Summary of dielectric parameters & d33 of (BZT-

BCT)-epoxy & (BZT-BCT)-(epoxy-CCTO) composite

systems with different vol. fractions of ceramics :

Materials Vol% of

ceramics

Parameters

r at RT at

1 kHz

tan at

RT at 1

kHz

rmax at 1

kHz

Tmax at 1

kHz

d33 in

pC/N

0.2(BZT-BCT)-

0.8[(1-x)epoxy-

xCCTO]

composites

x = 0.02 38 0.18 - - 5

x = 0.04 45 0.14 - - 7

x = 0.06 49 0.09 - - 10

x = 0.08 61 0.05 - - 15

x = 0.10 52 0.18 - - 13

Major Conclusions Drawn From the Present Work:

• 0.50BZT-0.50BCT system sintered at 1400oC showed better structural, microstructural, dielectric, ferroelectric and piezoelectric properties. •0.25(BZT-BCT)-0.75(PVDF) and 0.20(BZT-BCT)-0.80(epoxy) ceramic-polymer composites are suitable for capacitor & energy harvesting applications. •Dielectric and piezoelectric properties of [0.25(BZT-BCT)-0.69(PVDF)-0.06(CCTO)] and [0.20(BZT-BCT)-0.736(Epoxy)-0.064(CCTO)] ceramic-polymer composites are better than the existing reports and suggested their suitability for flexible capacitor devices and for energy harvesting piezoelectric applications.

27