Polar nature of (𝟏 − 𝒙)𝑩𝒂(𝒁𝒓𝟎.𝟐 𝑻𝒊𝟎.𝟖 )𝑶𝟑 − 𝒙(𝑩𝒂𝟎.𝟕 𝑪𝒂𝟎.𝟑 )𝑻𝒊𝑶𝟑 ceramics

near morphotropic phase boundary.

Smaranika Dash1, Ashok Kumar2, Shrabanee Sen3, Dillip K. Pradhan1*

1 Department of Physics and Astronomy, NIT Rourkela, Odisha-769008, India 2CSIR-NPL, Dr. K. S. Krishnan Marg, New Delhi-110012, India

3Sensor and Actuator Division, CSIR-CGCRI, Kolkata-700032, India

*Email of corresponding author: dillip.pradhan79@gmail.com

Ferroelectric materials have been extensively used in the multifunctional device applications such as

high energy density capacitors, sensors, actuators, random access memory. Recently, lead-free BaTiO3

based solution i.e., (1 − 𝑥)𝐵𝑎(𝑍𝑟0.2 𝑇𝑖0.8 )𝑂3 − 𝑥(𝐵𝑎0.7 𝐶𝑎0.3 )𝑇𝑖𝑂3 (BZT-BCT) received significant

attention because of high dielectric constant (𝜀𝑟 = 3060) and large piezoelectric properties (𝑑33 =

560 − 620 𝑝𝐶/𝑁) near morphotropic phase boundary (MPB). MPB separates two crystallographic

phases such as rhombohedral and tetragonal phase around which maximum dielectric and piezoelectric

properties are obtained. It has been reported that the crystal structure around MPB and its correlation

with the enhancement of properties have not been well studied. In view of this, we have prepared

polycrystalline samples of (1 − 𝑥)𝐵𝑎(𝑍𝑟0.2 𝑇𝑖0.8 )𝑂3 − 𝑥(𝐵𝑎0.7𝐶𝑎0.3 )𝑇𝑖𝑂3 (𝑥 = 0.4, 0.45, 0.48,

0.5, 0.52, 0.55, 0.6) by auto combustion technique. The phase formation and surface morphology, have

been studied using X-ray diffraction and FE-SEM analysis respectively. The temperature dependent

dielectric properties are studied using an Impedance analyzer from 100Hz to 1MHz. Measurement on

PE-hysteresis loop and piezoelectric properties are also performed at room temperature. The detailed

results will be discussed in the conference.

Keywords: Lead-free ferroelectric oxides, dielectric constant, crystal structure, morphotropic phase

boundary, ferroelectric properties.

Smaranika Dash1, H. S. Mohanty1, Ashok Kumar2, Shrabanee Sen3, Dillip K. Pradhan1*

1 Department of Physics and Astronomy, National Institute of Technology, Rourkela-769008, Odisha, India.2CSIR-National Physical Laboratory, Dr. K. S. Krishnan Marg, New Delhi-110012, India.3Sensor and Actuator Division, CSIR-CGCRI, Kolkata-700032, India.

Sample Synthesis

Preheated Furnace

Rapid heating

Aqueous redox

mixture

Aqueous redox

mixture

Combustion ResidueCombustion Residue

Calcination

(9000C)

Calcination

(9000C)

CharacterizationCharacterization

Oxidizer

(metal

nitrate)

Oxidizer

(metal

nitrate)

Titanium

Isopropoxide

Titanium

Isopropoxide

Urea

(Fuel)

Urea

(Fuel)

Stoichiometry (O/F)Stoichiometry (O/F)

Sintering (12000C)Sintering (12000C)

Characterisation Technique

Ch

ara

cter

isa

tio

n

StructuralStructural

Dielectric Dielectric

Ferroelectric

and I-V

characteristic

Ferroelectric

and I-V

characteristic

XRD (Rigaku

JAPAN Ultima-

IV, Cu Kα1,

λ=1.5405A0)

Impedance

analyser

Radiant

Ferroelectric

Tester

Conclusions• 0.45Ba(Zr0.2Ti0.8)O3-0.55(Ba0.7Ca0.3)TiO3 is synthesized by auto combustion technique and sintered using Microwave sintering

technique.

• XRD pattern confirms the formation of single phase of 0.45BZT-0.55BCT at room temperature.

• The phase transtion temperature of the poled sample as determined from the dielectric versus temperature curve is Tc~950C which

shows a higher dielectric constant (εr=5880) as compare to unpoled sample. From tangent loss curve, a low loss is observed around Tc

i.e. tanδ<0.03.

• A saturated ferroelectric behaviour for both poled and unpoled samples is observed. Low coercive field observed from PE loop

suggesting that the material is a soft ceramic.

• The I-V characteristic shows the symmetric behaviour for both poled and unpoled sample.

IntroductionRecently, lead-free BaTiO3 based solution i.e., 0.5Ba(Zr0.2Ti0.8 )O3 - 0.5(Ba0.7Ca0.3)TiO3 (BZT-BCT) received significant attention because of it’s high dielectric constant (εr=3060) and

large piezoelectric properties (d33=560-620 pC/N) near morphotropic phase boundary (MPB).

The synthesis method for BZT-BCT required very high temperature(1300-15000C) to get a phase pure material.

To improve the physical properties from application point of view, synthesis of high quality stoichiometric ceramics powder at lower temperature synthesis conditions and improved

microstructure is one of the essential requirements.

Microwave sintering (MW) process often involved in densification of pellets without grain growth, reduction in sintering temperature, shorten the sintering time to get fine, and

uniform grains with improved microstructure in comparison to conventional sintering (CS).

It is reported that the dielectric, piezoelectric and ferroelectricity for MW sintered samples were observed to be more as compared to CS ceramics.

These ferroelectric materials have wide range of device applications such as sensors, actuators, capacitors, RAM, detectors etc.

Results

The XRD pattern shows the formation

of single phase compound without the

presence of any trace of impurity.

A well defined ferroelectric hysteresis loop is

observed for both poled and unpoled sample. From

P-E loop, the ferroelectric parameters are derived.

The I-V characteristic shows the similar

behaviour for both positive and negative

applied electric field.

• The temperature dependent dielectric constant shows a transition from Ferroelectric to

Paraelectric phase.

• For poled sample of 0.45BZT-0.55BCT shows a higher dielectric constant around TC as

compare to unpoled sample.

The dielectric loss for poled sample is

nearly constant from room temperature

to 1500C.

• I. Coondoo, N. Panwar, H.Amorın, M. Alguero, and A. L. Kholkin , J. Appl. Phys. 113 (2013) 214107.

• W. Liu and X. Ren, Phys. Rev. Lett. 103 (2009) 257602.

• Ye Tian, L. Wei, X. Chao, Z. Liu, and Z. Yang, J. Am. Ceram. Soc. 96 [2] (2013) 496.

• K. Brajesh, K.Tanwar, M. Abebe, R. Ranjan, Phys. Rev. B 92 (2015) 224112

ReferencesSmaranika Dash thankfully acknowledge MHRD, India for research

fellowship.

Polar Nature of (1-x) Ba(Zr0.2Ti0.8 )O3- x (Ba0.7Ca0.3)TiO3 ceramic Near Morphotropic Phase Boundary

Acknowledgement

AbstractThe lead free polycrystalline ferroelectric samples of 0.45Ba(Zr0.2Ti0.8) O3-0.55(Ba0.7 Ca0.3)TiO3 have been synthesized by auto combustion technique. The room temperature XRD

pattern reveals the formation of single phase compound. The temperature dependent dielectric measurement for both poled and unpoled sample has been carried out. The temperature

dependent dielectric properties shows a high dielectric constant (ɛr) value of 5880 around Tc =950C (for poled) and 5869 around Tc =890C ( for unpoled) sample. The I-V characteristic

shows a symmetric behaviour for both positive and negative applied electric field. The sample shows a saturated ferroelectric behaviour for both poled and unpoled case. From P-E

hysteresis loop, the remnant polarisation (2Pr0) and coercive field (Ec

0) for are found to be 5.39μC/cm2, 4.672 kV/cm (poled sample ) and 3.44 μC/cm2, 3.893 kV/cm (unpoled sample )

respectively.

(300

)

20 30 40 50 60 70 80

Inte

ns

ity

(a

rb.u

nit

)

2 (degree)

0.45Ba(Zr0.2

Ti0.8

)O3-0.55(Ba

0.7Ca

0.3)TiO

3

(110)

(100

)

(111

)

(200

)

(210

) (211

)

(220

)

(310

)

(311

)

-60 -40 -20 0 20 40 60

-15

-10

-5

0

5

10

15

P(

C/c

m2

)

E(kV/cm)

unpoled at 10 Hz

poled at 10Hz

0.45Ba(Zr0.2

Ti0.8

)O3-0.55(Ba

0.7Ca

0.3)TiO

3

0 50 100 150 200 250 300

1000

2000

3000

4000

5000

6000

Die

lect

ric

con

sta

nt( r

)

Temperature (0C)

1kHz

5 kHz

10 kHz

50 kHz

100 kHz

500 kHz

1 MHz

Unpoled

0 50 100 150 200 250

1000

2000

3000

4000

5000

6000

Die

lectr

ic C

on

sta

nt( r

)

Temperature (0C)

1kHz

5kHz

10kHz

50kHz

100kHz

500kHz

1MHz

Poled

0 50 100 150 200 2501E-3

0.01

0.1

1

tan

Temperature (0C)

1 kHz

5 kHz

10 kHz

50 kHz

100 kHz

500 kHz

1 MHz

0.45Ba(Zr0.2

Ti0.8

)O3-0.55(Ba

0.7Ca

0.3)TiO

3

poled

P360

-60 -40 -20 0 20 40 601x10

-11

1x10-10

1x10-9

1x10-8

1x10-7

1x10-6

cu

rren

t d

en

sit

y J

(A/c

m2

)

E(kV/cm)

Unpoled at 10 Hz

Poled at 10 Hz

* dillip.pradhan79@gmail.com