ceramics, electrical properties, microstructure, electrical conductivity
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.
Tsinghua University Press
Lalatendu BISWAL, Piyush R. DAS, Banarji BEHERA. Frequency dependent electrical properties of Na2Pb2R2W2Ti4Nb4O30 (R = Nd, Sm) ceramics. Journal of Advanced Ceramics 2014, 3(3): 215-223.