Indentation damage zone in calcium and lead titanate ceramics

Indentation cracks are driven to their equilibrium length by residual stres ses produced by the plastic zone beneath the indenter. In the present study , the shape and size of this zone for several lead titanate based materials were investigated. These materials have a range of tetragonal distortions, or c/a ratios. For isotropic unpoled samples the size of the plastic zone can be predicted by elastoplastic theory. The shape of the plastic zone for poled materials is slightly elliptical with the long and short axes perpen dicular and parallel to the poling direction respectively.