Structure and Piezoelectric Properties Near the Bismuth Scandium Oxide-Lead Zirconate-Lead Titanate Ternary Morphotropic Phase Boundary

Ternary phase diagram of BiScO3 (BS), PbZrO3 (PZ), and PbTiO3 (PT) was explored for identification of high-performance piezoelectrics for actuator applications. The ternary morphotropic phase boundary (MPB) connecting the binary MPBs of BS-PT (45/65) and PZ-PT (52/48) was determined using X-ray diffraction (XRD). High-temperature XRD and dielectric measurements were used to determine the phase transformation temperatures. Curie temperature (T-C) had a near linear dependence on composition, rate of which is determined for each component of the ternary independently. Specimens on the tetragonal side of the MPB exhibited lower high field resistivity and proper poling was not possible. Specimens on the rhombohedral side were superior with saturated hysteresis loops and piezoelectric coefficient (d(33))> 400 pm/V. Unlike phase transformation temperatures, the proximity to MPB was more dominant than the compositional effects in determining electrical and electromechanical properties, which maximized for the compositions closest to the MPB. Both weak- and high field properties are reported as a function of temperature.