Stabilization of metastable tetragonal phase in a rhombohedral magnetoelectric multiferroic BiFeO₃–PbTiO₃

Abstract

The phase formation behaviour of the magnetoelectric multiferroic 0.8BiFeO₃–0.2PbTiO₃ was studied as a function of heat treatment at different temperatures of a sol–gel derived powder. While under ordinary synthesis conditions this composition exhibits antiferromagnetic ordering and a rhombohedral structure; the sol–gel-enabled low-temperature synthesis could stabilize a tetragonal metastable phase along with the stable rhombohedral phase, mimicking a morphotropic phase boundary state. The phase coexistence state exhibits relatively enhanced ferromagnetic correlation. The same system with a relatively higher PbTiO₃ concentration, 0.65BiFeO₃–0.35PbTiO₃, on the other hand, exhibits a rhombohedral metastable phase. These results suggest that the occurrence of metastable phases is a very common feature in the BiFeO₃–PbTiO₃ magnetoelectric ferroelectric system and that it affects the ferroelectric and magnetic properties of system quite remarkably.