Crystal growth and mechanical properties of Pb[(Zn1/3Nb2/3)0.91Ti0.09]O3 single crystal produced by solution Bridgman method

High-quality, 40-mm-diameter piezoelectric Pb[(Zn1/3Nb2/3)(0.91)Ti-0.09]O-3 single crystals (PZNT91/9) were successfully grown by the solution Bridgman method. Vickers hardness and fracture toughness of a PZNT91/9 wafer cut from a crystal were investigated by a microindentation technique. The Vickers hardness of PZNT91/9 was 2.6 GPa. (transparent area) and 2.2 GPa (opaque area). The Vickers hardness of the transparent area in PZNT91/9 was equivalent to that of PZT ceramic. The fracture toughness of the transparent area of PZNT91/9 was markedly different depending on the domain direction: K-IC = 0.80 MPa.m(1/2) (vertical to the domain wall); and K-IC = 0.38 MPa.m(1/2) (parallel to the domain wall). Although the fracture toughness of PZNT91/9 is smaller than that of PZT ceramic, it is possible to cut the crystals for fine-pitch dicing, as required to produce array-type medical transducers, without serious problems.