Impedance and dielectric studies of ferroelectric SrBi2Nb2O9 ceramics Original Research Article

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*=R0/(1+(iω/ω1)m+(iω/ω2)n) [J. Phys. Chem. Solids 53 (1992) 1] where ω1 and ω2 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, Tc (723 K) whereas the m was temperature independent.