Domain Switching and Microcracking in Ferroelectric Single Crystals and Polycrystalline Ceramics

Abstract

In polycrystalline piezoelectric ceramics, electric field-induced cracking occurred by intergranular fracture. The macroscopic path of the crack growth depended strongly upon the applied field and the poling direction. Analysis showed that cracks extended along the place of maximum normal strain. Mechanisms for the intergranular fracture were investigated by the in-situ TEM technique. During electrical cycling, transient dielectric breakdown and local melting in the amorphous grain boundary layers were the likely precursors to fracture. Assisted by the incompatible stresses, cavitation took place. The increase of the density and the linkage of these cavities weakened the grain boundary, leading to crack growth along the boundary.