Fracture toughness anisotropy of PZT

Fracture toughness of a lead zirconate titanate (PZT) piezoelectric was measured using the indentation technique and the single edge notch bend (SENB) method. Values of fracture toughness, KIc, show significant anisotropy in poled samples, with longest and shortest crack lengths in the directions parallel and perpendicular to the poling axis, respectively. The crack profiles below the indented surfaces have been studied for both the unpoled and the poled samples. This also revealed the shape and size of the plastically deformed zone underneath the indentation. The microstructural anisotropy and internal stresses caused by the poling, and the contribution of stresses introduced by the experimental method are considered in the discussion.