Strain evolution from ferroelectric to relaxor state in BiFeO3-BaTiO3 based ceramics

Abstract

BiFeO₃ (BF)-based lead-free piezoelectric ceramics have been already widely exploited. In order to reduce the leakage current and resolve the problem of difficult polarization, BaTiO₃ (BT) has been added to form the BiFeO₃-BaTiO₃(BF-BT) solid solution. The piezoelectric and ferroelectric properties have been greatly improved with modified phase structure and relaxor characteristics of BF-BT ceramics by ions doping. The mechanism of strain response from the ferroelectric to relaxor state in BF-BT based ceramics has not been thoroughly investigated. This work emphasizes on the evolution of strain from ferroelectric-relaxor state in (0.67-x)BF-0.33BT-xBMZ ceramics. Three states of ferroelectric-relaxor with strengthening relaxor are constructed via increasing Pm3m and reducing R3m symmetry. A tendency of increasing first and then decreasing is obtained for S_uni and S_pos with enhanced relaxor behavior along with a maximum strain (S_uni = 0.25%, S_pos = 0.24%) for x = 0.04, due to the promoted domain switching and strong random field with appropriate polar nanoregions merged into long-range ordered matrix. And the strain gradually increases with elevating temperature due to the improved polarization and growing ferroelectric domain. This study reveals the contribution of structure modification to piezoelectric response, promoting the development of lead-free piezoelectrics.