Kinetics of phase transformation at the Curie point of ferroelectric ceramic Ba0.8Sr0.2TiO3

Abstract

The temperature dependences of the dielectric permittivity and dielectric loss tangent in the ferroelectric ceramic Ba0.8Sr0.2TiO3 have been studied at frequencies from 25 Hz to 120 Hz. It was found that the phase transition at the Curie point (ТС ≈ 338 K) is diffused in the temperature range of ∼ 30 K. The temperature dependence of the local order parameter plotted based on dielectric measurement data confirms the diffusion of the phase transition, which begins by the arising of local polar regions at Burns temperature. The revealed dependences of the dielectric loss maximum near the TC on the heating rate of the sample and frequency are well explained in the framework of the fluctuation model of low-frequency dielectric losses during a first-order phase transitions.