Electric field-temperature phase diagram and electrical properties of (1-x)Na0.5Bi0.5TiO3 - xK0.5Bi0.5TiO3 ceramics

Abstract

Electrically and thermally induced transitions between ferroelectric and relaxor states are of great significance in Na1/2Bi1/2TiO3 (NBT)-based materials due to their remarkable similarity to electromechanical properties. However, an in-depth understanding of the family of this material remains challenging, primarily due to its structural complexity and diverse behaviour with or without the presence of an external electric field. For enhancing NBT-based ceramics and enabling the analysis of their electric field temperature (E-T) phase diagrams, it has been suggested that K0.5Bi0.5TiO3 (KBT) could be used as a dopant material. This study thoroughly examines the electrical, microstructural, and ferroelectric (FE) properties of (1-x)NBT-xKBT ceramics. The incorporation of KBT into NBT, inducing a change in structural symmetry, reveals the coexistence of rhombohedral and tetragonal phases (x ∼ 0.2), as confirmed by X-ray diffraction. Using a modified KWW function, electrical modulus (EM) analysis illustrates a non-Debye-type relaxation process. Moreover, it is observed that temperature influences the transition of the material among its ferroelectric (FE), ergodic (ER), and non-ergodic (NR) relaxor phases. This report proposes that the E-T phase diagram can serve as a valuable tool for determining optimal conditions and selecting materials for electromechanical and actuator-based applications.