Frequency dependence of the dielectric properties of ferroelectric Bi2VO5.5 ceramics

The dielectric properties of ferroelectric Bi2VO5.5 (BiV) ceramics in the frequency range of 100 Hz to 10 MHz at various temperatures (300 K to 800 K) have been studied. A strong low frequency dielectric dispersion (LFDD) is found to exist in these ceramics. The frequency characteristics of the capacitance of BiV samples under study show universal dynamic response of the form, C* = A(T)(i omega)(n(T)-1), proposed by Jonscher for the systems with quasi-foe charges. The dielectric data obtained in the measured frequency and temperature ranges have been found to fit very well to the dielectric dispersion relations: epsilon(r)(1) = epsilon(infinity) + sin(n(T)pi/2)omega(n(T)-1)a(T)/epsilon(0) and epsilon(r) '' = sigma(epsilon 0 omega) + cos(n(T)pi/2)omega(n(T)-1)a(T)/epsilon(0). The coefficient A(T) (=a(T)S/L) and the exponent n(T) of the Jonscher's expression are determined from the curve fitting. The characteristic exponent n(T) is found to have a minimum at the Curie temperature, T-c (725 K). The parameter 'A(T)' shows a prominent peak in the vicinity of the Curie temperature.