R-Curve Behavior of Pb(Mg1/3Nb2/3)O3-29 mol% PbTiO3 Single Crystals: The Effect of Crystallographic Orientation and Grain Structure

The crack growth resistance behavior of single crystal and polycrystalline 0.71Pb(Mg1/3Nb2/3)O3‐0.29PbTiO3 (PMN‐29%PT) was determined with compact‐tension specimens. Two different single crystal orientations were produced by the solid‐state crystal growth technique (SSCG) and characterized, allowing for the direct comparison to polycrystalline material. Single crystal R‐curve behavior was observed to be anisotropic, which is explained by the effects of ferroelasticity and stress‐induced phase transformations on toughening. Results of the polycrystalline samples display comparable toughness to that observed in single crystal measurements.