Impedance and dielectric studies of ferroelectric SrBi2Nb2O9 ceramics

This paper reports the dielectric and impedance characteristics of ferroelectric SrBi2Nb2O9 (SBN) ceramics in the 100 Hz-1 MHz frequency range at various temperatures (300- 823 K). A strong low frequency dielectric dispersion (LFDD) associated with an impedance relaxation has been found to exist in these ceramics in the temperature range 573-823 K. The Z" of the AC complex impedance showed two distinct slopes in the frequency range 100 Hz-1 MHz suggesting the existence of two dispersion mechanisms. This non-ideal behavior has been explained on the basis of the expression, Z* = R-0/(1 + (iomega/omega(1))(m) + (iomega/omega(2))(n)) [J. Phys. Chem. Solids 53 (1992) 1] where omega(1) and omega(2) characterize the lattice response and the charge carrier behavior, respectively. The exponents m and n were obtained from the curve fitting. The exponent n was found to exhibit a minimum at the Curie temperature, T-c (723 K) whereas the m was temperature independent. (C) 2003 Elsevier Ltd. All rights reserved.