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)O-3-0.29PbTiO(3) (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.