Optimization of Ferroelectric Ordering and Thermal Stability in Na<sub>1/2</sub>Bi<sub>1/2</sub>TiO<sub>3</sub>-Based Lead-Free Single Crystal through Defect Engineering
Chao Chen, Yang Li, Zhenxiang Cheng, Saisai Chang, Xingan Jiang, Xiangping Jiang, Jianli Wang, Xiaokun Huang, Xiaoyi Gao, Guangzhi Dong, Haosu Luo, Yanhong Lyu, Jun‐Ming Liu, Shujun Zhang
Abstract
Environmentally friendly lead-free piezoelectric materials have been attracting significant attention in recent years. Na1/2Bi1/2TiO3-based relaxor ferroelectrics have found acceptance for application in promising lead-free transducers in high-power ultrasonic devices. However, their low thermal stability, i.e., their relatively low ferroelectric-relaxor transition temperature (TF-R), hinders their practical application. Herein, a thermal-quenching approach is applied on a Na1/2Bi1/2TiO3 (NBT)-based single crystal, which yields a large increase in TF-R and dramatic enhancement of its ferroelectric ordering, leading to excellent thermal stability of its dielectric, ferroelectric, and piezoelectric properties. This behavior is mainly attributed to quenching-induced domain evolution as well as its octahedral tilt, which is linked to the increased oxygen vacancies. The substitution of long-range ordered ferroelectric domains for short-range polar nanodomains contributes to its increased coherence length and, consequently, enhancement of TF-R. This work provides an approach to the optimization of the ferroelectric ordering and thermal stability of NBT as well as an in-depth understanding of the quenching effect on the local structure, which could be applied to other relaxor-based ferroelectrics for optimization of their macroscopic properties.