Equilibrium phases in the multiferroic BiFeO3-PbTiO3system – a revisit

V Kothai,A Senyshyn,R Ranjan,D Niarchos,O Kalogirou,G Hadjipanayis

doi:10.1051/epjconf/20147509003

Abstract

The(1-x) BiFeO3-(x) PbTiO3 solid solution exhibiting a Morphotropic Phase Boundary (MPB) has attracted considerable attention recently because of its unique features such as multiferroic, high Curie point (T-C similar to 700 degrees C) and giant tetragonality (c/a -1 similar to 0.19). Different research groups have reported different composition range of MPB for this system. In this work we have conclusively proved that the wide composition range of MPB reported in the literature is due to kinetic arrest of the metastable rhombohedral phase and that if sufficient temperature and time is allowed the metastable phase disappears. The genuine MPB was found to be x=0.27 for which the tetragonal and the rhombohedral phases are in thermodynamic equilibrium. In-situ high temperature structural study of x=0.27 revealed the sluggish kinetics associated with the temperature induced structural transformation. Neutron powder diffraction study revealed that themagnetic ordering at room temperature occurs in the rhombohedral phase. The magnetic structure was found to be commensurate G-type antiferromagnetic with magnetic moments parallel to the c-direction (of the hexagonal cell). The present study suggests that the equilibrium properties in this solid solution series should be sought for x=0.27.

Highlights

The solid solutions of (1-x) BiFeO3-(x) PbTiO3 were prepared by conventional solid state route
The stability of the two-phase nature (P4mm + R3c) even after 16 hours of sintering at 990°C suggests that for this composition both the phases are in equilibrium. x = 0.27 can be considered as the genuine Morphotropic Phase Boundary (MPB) state of this solid solution series
A careful sintering time-temperature study of the reported MPB compositions of BiFeO3-PbTiO3 resolved the issue with regard to its erratic phase formation behaviour

Summary

Introduction

The solid solutions of (1-x) BiFeO3-(x) PbTiO3 were prepared by conventional solid state route. Abstract.The(1-x) BiFeO3-(x) PbTiO3 solid solution exhibiting a Morphotropic Phase Boundary (MPB) has attracted considerable attention recently because of its unique features such as multiferroic, high Curie point (TC ~ 700°C) and giant tetragonality (c/a -1 ~ 0.19). In this work we have conclusively proved that the wide composition range of MPB reported in the literature is due to kinetic arrest of the metastable rhombohedral phase and that if sufficient temperature and time is allowed the metastable phase disappears. The genuine MPB was found to be x=0.27 for which the tetragonal and the rhombohedral phases are in thermodynamic equilibrium.

Results

Conclusion