Electrostriction in Perovskite-Type Ferroelectric Ceramics

Abstract

The electrostriction and polarization in the perovskite-type ferroelectric ceramics have been calculated in the state under the arbitrary biasing field. Domain configurations produced by 180°-reversal or 90°-rotation have been represented here by the threshold angle θ 180 or θ 90 ; that is, domains, making smaller angles than θ 180 or θ 90 after the switching once occurs, are completely reoriented under the given bias. The electrostriction and polarization can be calculated as functions of θ 90 and θ 180 , from the spontaneous strain and polarization of the crystal. The spontaneous strain in the rhombohedral crystal has been found as (3/2)[(π/2)-α] for the first time. Bias dependence of θ 90 and θ 180 have been obtained from the experimental results on the basis of the present calculations. Some discrepancies between the results and the expectation based on the activation field considerations are presumably due to the mechanical stress accompanied with 90°-rotations, and to the interaction of 180°-reversals and 90°-rotations.