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In the present research work, frequency dependent electrical properties of tungsten bronze structured compounds Na2Pb2R2W2Ti4Nb4O30 (R = Nd, Sm) are reported. X-ray diffraction (XRD) study of polycrystalline ceramic samples confirms the formation of compounds with orthorhombic structure. Analysis of frequency dependent electrical data in the framework of modulus and conductivity formalism suggests the presence of thermally activated relaxation process in the compounds, which show Arrhenius behavior. The magnitudes of activation energies give the nature of the relaxing species. The real and imaginary parts of complex modulus trace the depressed semicircle in complex plane, suggesting non-Debye type relaxation process in the materials. The power law behavior of admittance data is successfully modeled by introducing constant phase element (CPE) to the equivalent circuit. A large value of power law parameter (n) of CPE below ferroelectric transition temperature (Tc) is attributed to the cooperative response of the dipoles which is reduced above Tc. This behavior is correlated with the frequency dependence of CPE, suggesting a physical meaning to it. The frequency dependent AC conductivity at different temperatures follows Jonscher’s universal power law. Almond and West formalism is used to estimate the hopping rate, activation enthalpy and charge carrier concentration in the materials.


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Frequency dependent electrical properties of Na2Pb2R2W2Ti4Nb4O30 (R = Nd, Sm) ceramics

Show Author's information Lalatendu BISWALa,cPiyush R. DASb( )Banarji BEHERAc
Department of Physics, SOT, KIIT University, Bhubaneswar-751024, Odisha, India
Department of Physics, Veer Surendra Sai University of Technology, Burla-768018, Sambalpur, India
School of Physics, Sambalpur University, Jyoti Vihar, Burla-768019, Odisha, India

Abstract

In the present research work, frequency dependent electrical properties of tungsten bronze structured compounds Na2Pb2R2W2Ti4Nb4O30 (R = Nd, Sm) are reported. X-ray diffraction (XRD) study of polycrystalline ceramic samples confirms the formation of compounds with orthorhombic structure. Analysis of frequency dependent electrical data in the framework of modulus and conductivity formalism suggests the presence of thermally activated relaxation process in the compounds, which show Arrhenius behavior. The magnitudes of activation energies give the nature of the relaxing species. The real and imaginary parts of complex modulus trace the depressed semicircle in complex plane, suggesting non-Debye type relaxation process in the materials. The power law behavior of admittance data is successfully modeled by introducing constant phase element (CPE) to the equivalent circuit. A large value of power law parameter (n) of CPE below ferroelectric transition temperature (Tc) is attributed to the cooperative response of the dipoles which is reduced above Tc. This behavior is correlated with the frequency dependence of CPE, suggesting a physical meaning to it. The frequency dependent AC conductivity at different temperatures follows Jonscher’s universal power law. Almond and West formalism is used to estimate the hopping rate, activation enthalpy and charge carrier concentration in the materials.

Keywords:

ceramics, electrical properties, microstructure, electrical conductivity
Received: 15 March 2014 Revised: 09 June 2014 Accepted: 12 June 2014 Published: 02 September 2014 Issue date: September 2014
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Publication history

Received: 15 March 2014
Revised: 09 June 2014
Accepted: 12 June 2014
Published: 02 September 2014
Issue date: September 2014

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