Electroacoustic echoes and dielectric nonlinearity at the ferroelectric phase transitions

Abstract

The temperature dependence of the dielectric nonlinearity at different bias electric fields has been measured in Cd₂Nb₂O₇ crystal. The maximum of the dielectric nonlinearity as a function of the bias field has been found in three crystallographic phases in Cd₂Nb₂O₇. The electroacoustic echo relaxation time T₂ in this crystal shows different character of the exciting pulse amplitude dependence at the diffuse phase transition (PT) as compared with temperatures below this PT. The new type of the electroacoustic echo ω-2ω-2ω has been observed in SbSI crystal near the ferroelectric PT temperature. The data obtained have been discussed taking into account the influence of the domain structure and heterophase structure changes on the dielectric nonlinearity.