Role of the third composition and its A-site cation off-centering mechanism in ternary BiFeO3‒BaTiO3-based piezoelectric ceramics

Abstract

Ternary BiFeO₃‒BaTiO₃ (BFBT)-based ceramics often exhibit a higher piezoelectricity compared to binary BFBT ceramics. However, the origin of the enhanced piezoelectricity in ternary ceramics remains unclear. In this study, we investigated the role of the third composition by examining the pseudo-cubic symmetry of Bi(Mg_0.5Ti_0.5)O₃ (BMT)-modified BFBT piezoelectric ceramics using high-energy synchrotron radiation X-ray diffraction and the Rietveld method. Our experimental results validate the critical influence of Bi ion off-centering displacement, as the largest Bi ion off-centering displacement at a specific third composition demonstrates the highest piezoelectric properties. The displacement of Bi ions varies with the Bi-O covalent bond length and repulsive interactions between the off-centered Bi and B-site cations. This study highlights the importance of the ionic radii of the B-site cations in the third composition for high-performance BFBT-based piezoelectric ceramics.