Local structure analysis of Bi_0.5Na_0.5TiO₃–BaTiO₃ solid solutions

Abstract

Solid solutions of Bi0.5Na0.5TiO3 (BNT) and BaTiO3 (BT) is known to possess good ferroelectric properties. 
 Local structural analysis and electronic structure analysis of the high-quality BNT–BT solid solutions were performed using synchrotron radiation X-rays, and the mechanism of ferroelectric enhancement was clarified. As the BT composition increased, the crystal structure became tetragonal with space groups P4bm and P4mm. Lattice contraction was observed in the high-temperature phase, suggesting that some randomness in the high-temperature phase freezes and couples with the disorder parameter in the BNT–BT. The local structural analysis showed that the introduction of the structural randomness helps to improve the ferroelectric properties of BNT--BT analogous to relaxor ferroelectrics. The BT substitution decreases the misalignment of TiO6 octahedron, which is the origins of the structural randomness of BNT. Therefore, optimization of the BT composition is necessary to improve the ferroelectric properties of the BNT–BT solid solution.