Structural phase transition study of the morphotropic phase boundary compositions of Na(0.5)Bi(0.5)TiO(3)-PbTiO(3).

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)TiO(3)-xPbTiO(3) 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 PbTiO(3) 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.