Transmission electron microscopy investigation of the high temperature BiScO3−PbTiO3 piezoelectric ceramic system

Recently, a perovskite solid-solution ((1−x)BiScO3−(x)PbTiO3) with superior electromechanical properties than PbZrO3−PbTiO3 (PZT) ceramics has been discovered. The system has a morphotropic phase boundary (MPB) between ferroelectric rhombohedral (R) and tetragonal (T) symmetries similar to PZT but the underlying domain structures and some aspects of the crystal chemistry remain to be elucidated. Therefore, transmission electron microscopy has been used to study changes in domain structure and symmetry as a function of x. Domain structures in the R and T phases have been found which closely resemble those in PZT. In addition, 12{hkl} superlattice reflections were observed, particularly in the 〈110〉 zone axis diffraction patterns from grains of the R phase (e.g., x=0.5), which were consistent with rotations of the octahedra in antiphase and the space group R3c. These reflections were absent in the R phase close to the MPB (x=0.64) and in the T phase (x=0.75). From these results, the low temperature phase diagram for BiScO3−PbTiO3 has been modified.