935.
This paper reports the dielectric and impedance characteristics of ferroelectric SrBi
2Nb
2O
9 (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.
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