Crystallite size dependence of morphotropic phase boundary in the multiferroic BiFeO3-PbTiO3

TL;DR

This study reveals that the phase boundary in BiFeO3-PbTiO3 multiferroic materials is strongly influenced by crystallite size, with larger grains stabilizing a pure phase and smaller grains showing phase coexistence, independent of internal stress.

Contribution

It demonstrates that crystallite size, rather than internal stress, controls the phase stability at the morphotropic boundary in BiFeO3-PbTiO3.

Findings

Large grains (~10 microns) exhibit pure tetragonal phase.

Smaller grains (~1 micron) show phase coexistence.

Crystallite size, not internal stress, determines phase stability.

Abstract

The morphotropic phase boundary (MPB) in the magnetoelectric multiferroic BiFeO3-PbTiO3 is shown to be uniquely dependent on crystallite size. The system exhibits the phenomenon of abnormal grain growth (AGG) during sintering with abrupt increase in the grain size from ~ 1 micron to ~ 10 microns. The large sized free crystallites (10 microns) exhibit pure tetragonal phase. Phase coexistence sets in after reducing the size to ~ 1 micron. These results prove that size, and not the internal stress, as the controlling mechanism for stabilizing phase coexistence in this system.