Ternary phase diagram and dielectric behavior of BiFeO3-BaTiO3-SrTiO3 solid solutions

Abstract

Ternary phase diagrams and dielectric properties of BiFeO3-BaTiO3-SrTiO3 (BF-BT-ST) solid solutions were calculated by phenomenological theory, and crystal structures and dielectric characteristics of BF-BT-ST ceramics via solid-state reaction method were also investigated. Rhombohedral, tetragonal and cubic phase can exist at room temperature, and cubic phase region expands as the temperature rises. Room temperature and high temperature XRD of BF-BT-ST ceramics near the computed phase boundary confirm such phase diagrams, meanwhile suggesting that the real phase boundary is broad. The tendency of measured permittivity of BF-BT-ST ceramics is consistent with that of theoretical result, indicating that high permittivity occurs at the phase boundary of rhombohedral and cubic phase, or tetragonal and cubic phase. Furthermore, dielectric properties of BF-BT-ST ceramics exhibit the feature of relaxor ferroelectrics, which is verified by XRD and Raman analysis. This research establishes ternary phase diagram of BF-BT-ST solid solutions, and helps to understand their dielectric relaxation behavior.