Phase and defect structures of MnO <sub>2</sub> ‐doped 75BiFeO <sub>3</sub> –25BaTiO <sub>3</sub> ceramics and their effects on electrical properties
Lin Tang, Xuefan Zhou, Muhammad Habib, Qijun Wang, Guoliang Xue, Yan Zhang, Xi Yuan, Dou Zhang
Abstract
Abstract Bismuth ferrite (BiFeO 3 )‐based high‐temperature piezoelectric ceramics have high Curie temperatures and excellent thermal stability; however, their applications are limited by inadequate piezoelectric performance due to large coercive fields and high leakage conduction. This study investigates the impact of MnO 2 doping on the phase transition, defect structure, domain morphology, as well as the dielectric, ferroelectric, and electrical conduction behaviors of 75BiFeO 3 –25BaTiO 3 ceramics sintered under an oxygen atmosphere. A structural transformation from distorted rhombohedral to pseudo‐cubic symmetry was observed with increasing MnO 2 content, accompanied by domain fragmentation. MnO 2 doping at an appropriate level inhibited defects such as and . Regarding electrical properties, the reduction in rhombohedral distortion and enhancement in the pseudo‐cubic phase after MnO 2 doping resulted in decreased remanent polarization and electrostrain, which could potentially hinder piezoelectric response. However, appropriate MnO 2 doping effectively reduced leakage conduction, significantly enhancing the poling efficiency of the ceramics. The maximum d 33 value of 107 pC/N and k p of 0.36 were achieved at an MnO 2 doping content of 0.1 wt.%. Excessive MnO 2 addition may generate defect dipoles, as indicated by increased coercive field ( E c ) and dielectric loss. The observed increase in high‐temperature resistivity with MnO 2 content is primarily attributed to reduced grain size and increased concentration of mobile defects. This study provides valuable insights for further research on the application of 75BiFeO 3 –25BaTiO 3 systems in high‐temperature piezoelectric devices.