Dielectric and structural relaxation phenomena in Na_0.5Bi_0.5TiO₃single crystal

Abstract

Abstract Dielectric permittivity studies of Na0.5Bi0.5TiO3 single crystals in a broad range of frequency up to 10 MHz and temperature 300—823 K are reported. In this temperature range dielectric dispersion below 1 MHz has been found. The obtained data were fitted to the Cole-Cole relation. The mean relaxation time τ is strongly temperature dependent (0.04 − 2.6 × 10−5 s). A remarkable hysteresis effect in the values of τ on cooling and heating took place. The Δε(T) dependence (the maximal value of Δε ∼ 400) is similar to the global ε′(T) response at low frequency. An isothermal structural transformation in Na0.5Bi0.5TiO3 was observed by X-ray measurements. The order of the time in which the transformation takes place (∼300 minutes) corresponds to the time in which the strongest time evolution of electric permittivity and time changes of dielectric dispersion were detected.