Crack propagation in piezoelectric ceramics under pure mechanical loading

Abstract

The crack propagation behavior in piezoelectric lead zirconate titanate (PZT) ceramics is studied. The crack propagation in piezoelectric ceramics under pure mechanical loading is considered in which a mode I mechanical loading is applied by means of Vickers indentation. Anisotropy in crack propagation is characterized by measuring the length of cracks in two mutually orthogonal directions. Residual stresses in the PZT are also characterized by an indentation technique. The results indicate that as-fired and unpoled piezoelectric ceramics are isotropic in properties and under compressive state of residual stress. Poling introduces an anisotropy in crack propagation and changes the residual stress state. A compressive state of residual stress in the poling direction and a tensile stress state perpendicular to the poling direction are measured. This change in the residual stress state is related to the 90° domain reorientation and associated dimensional change induced by the applied electric fields during poling. It is concluded that the anisotropy in crack propagation cannot be explained by the residual stresses present in the poled PZT ceramics, but may be explained by the domain switching mechanism.