Microhardness and fracture toughness of 〈1 1 1〉-oriented Pb(Zn1/3Nb2/3)O3–PbTiO3 single crystal

Novel relaxor ferroelectric single crystal (1−x)Pb(Zn1/3Nb2/3)O3–xPbTiO3 (PZNT) was grown by vertical Bridgman method, the mechanical properties of the (1 1 1) face were systematically researched using microindentation technique. It was found that the Vickers’ microhardness Hv was as a function of the applied load. In the range of 0.1–3 kg, Hv was decreased from 4.03 to 3.26 GPa. The dependence of Hv on applied load could be explained on the basis of Kickʹs law, and the Meyer index n was determined to be 1.88. In-plane crack anisotropy behavior was observed on the wafer, the crack length in the direction parallel to domain wall was longer than that perpendicular to it, therefore, the (1 1 1) PZNT crystal displayed fracture toughness Kc anisotropy accordingly. The crack types (radial-median and Palmqvist systems) parallel and perpendicular to the domain wall in the 0.1–3 kg load range were classified.