Structures and electrical characterizations of high-Curie temperature (Na0.5Bi0.5)TiO3–PbTiO3 low-lead single crystals with compositions near the morphotropic phase boundary

Abstract

A series of (Na0.5Bi0.5)TiO3–PbTiO3 (NBT–PT) single crystals with compositions near the morphotropic phase boundary (MPB) region were grown by the modified Bridgman technique. The dependence of structure on composition was measured, and the MPB region of the NBT–PT system was confirmed. The dielectric properties of the NBT–PT single crystals were investigated, and the phase transition behaviour of the NBT–PT single crystals during heating was examined. With increasing addition of PT, the coercive field of the NBT–PT crystals decreased to levels much lower than that of the pure NBT system; such a change allowed easy poling of the NBT–PT crystals and the resultant piezoelectric properties were significantly enhanced. The electromechanical coupling factor of the crystals showed relatively constant thermal stability at the depolarization temperature (Td). Finally, studies of the domain evolution of NBT–0.09PT showed the disappearance of domains at the Td, which indicates that phase transition at the Td is related to changes in domain structures.