Polar nature of ( β )( . . ) β ( . . ) ceramics near morphotropic phase boundary. Smaranika Dash 1 , Ashok Kumar 2 , Shrabanee Sen 3 , Dillip K. Pradhan 1* 1 Department of Physics and Astronomy, NIT Rourkela, Odisha-769008, India 2 CSIR-NPL, Dr. K. S. Krishnan Marg, New Delhi-110012, India 3 Sensor and Actuator Division, CSIR-CGCRI, Kolkata-700032, India *Email of corresponding author: [email protected]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 β )( 0.2 0.8 ) 3 β ( 0.7 0.3 ) 3 (BZT-BCT) received significant attention because of high dielectric constant (= 3060) and large piezoelectric properties ( 33 = 560 β 620 /) 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 β )( 0.2 0.8 ) 3 β ( 0.7 0.3 ) 3 ( = 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.
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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 KΞ±1,
Ξ»=1.5405A0)
Impedance
analyser
Radiant
Ferroelectric
Tester
Conclusionsβ’ 0.45Ba(Zr0.2Ti0.8)O3-0.55(Ba0.7Ca0.3)TiO3 is synthesized by auto combustion technique and sintered using Microwave sintering
technique.
β’ XRD pattern confirms the formation of single phase of 0.45BZT-0.55BCT at room temperature.
β’ 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 (Ξ΅r=5880) as compare to unpoled sample. From tangent loss curve, a low loss is observed around Tc
i.e. tanΞ΄<0.03.
β’ 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.
β’ 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 itβs high dielectric constant (Ξ΅r=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.
β’ The temperature dependent dielectric constant shows a transition from Ferroelectric to
Paraelectric phase.
β’ 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.
β’ I. Coondoo, N. Panwar, H.AmorΔ±n, M. Alguero, and A. L. Kholkin , J. Appl. Phys. 113 (2013) 214107.
β’ W. Liu and X. Ren, Phys. Rev. Lett. 103 (2009) 257602.
β’ Ye Tian, L. Wei, X. Chao, Z. Liu, and Z. Yang, J. Am. Ceram. Soc. 96 [2] (2013) 496.
β’ 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 (Ιr) 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 5.39ΞΌC/cm2, 4.672 kV/cm (poled sample ) and 3.44 ΞΌC/cm2, 3.893 kV/cm (unpoled sample )