Structural phase transition study of the morphotropic phase boundary compositions of Na_0.5Bi_0.5TiO₃–PbTiO₃

Abstract

Neutron, synchrotron x-ray powder diffraction and dielectric studies have been performed for morphotropic phase boundary (MPB) compositions of the (1-x)Na(_1/2)Bi(_1/2)TiO₃-xPbTiO₃ system. At room temperature, the MPB compositions (0.10<x≤0.15) consist of a mixture of rhombohedral (space group R3c) and tetragonal (space group P4mm) structures with the fraction of tetragonal phase increasing with increasing PbTiO₃ content. On heating, while the rhombohedral phase just outside the MPB region, i.e. x = 0.10, transforms directly to a cubic phase, the rhombohedral phase of the MPB compositions transforms gradually to a tetragonal phase, until interrupted by a rhombohedral-cubic phase transition. The correspondence of the dielectric anomalies with the structural transitions of the different compositions has been examined and compared with earlier reports.