Research Status of Doping Modification of Bismuth Sodium Titanate Based Lead-free Piezoelectric Ceramics

Lead-free piezoelectric ceramics based on bismuth sodium titanate (Bi0.5Na0.5TiO3, 0.5 Na 0.5 TiO 3 , BNT) are increasingly popular in aerospace, naval sonar, high-speed trains, and electronic devices due to their environmental friendliness and outstanding ferroelectric capabilities. To address the challenge of high coercive fields and enhance electrical performance, doping modification of BNT-based ceramics introduces a morphotropic phase boundary (MPB) featuring both rhombohedral and tetragonal phases, effectively reducing the coercive field and significantly boosting electrical properties. This modification is essential for advancing the performance of sodium bismuth titanate-based lead-free piezoelectric ceramics. This paper provides an extensive review of the latest advancements in the field of BNT-based lead-free piezoelectric ceramics, with a focus on multi-component modifications, A / B-site ion doping, and rare earth ion doping. Findings indicate that incorporating appropriate components into BNT-based ceramics facilitates the formation of an MPB, which not only reduces the coercive field but also significantly improves the piezoelectric and ferroelectric properties of these materials. However, despite these advancements, piezoelectric ceramic development represents just a fraction of the piezoelectric materials landscape, with vast potential for further exploration. Doping with A- and B-site ions in BNT ceramics aims to maintain cellular structure stability, aligning with the consistency of ionic radius and electric valence. A-site doping mitigates the volatilization of Bi and Na elements and eases sintering challenges, significantly enhancing piezoelectric and ferroelectric properties while reducing the coercive field. B-site ion doping, through Ti4+ 4+ substitution, introduces defects and A-site vacancies, improving the piezoelectric constant d33. 33 . While these modifications have significantly advanced the structure and performance of BNT-based ceramics, issues with temperature stability remain, limiting their immediate practical application. Rare earth ion doping introduces light-emitting capabilities to BNT-based lead-free piezoelectric ceramics alongside piezoelectric improvements, significantly affecting their photoelectric properties. These diverse modification strategies collectively elevate the performance of BNT-based lead-free piezoelectric ceramics, paving the way for further research and potential practical applications. To advance the electrical performance of BNT-based lead-free piezoelectric ceramics, future research should focus on the material's intrinsic properties, specifically uncovering the physical nature of the quasi-isotropic phase boundaries and their role in enhancing electrical performance. This involves examining the changes in piezoelectric, ferroelectric, and dielectric properties across the MPB phase boundary range, as well as their dynamic evolution under external electric fields. Additionally, the research should explore the physical mechanisms by which component adjustments influence the stability of the material's phase structure, the regulation of the ferroelectric domain structure, and piezoelectric properties. Through these studies, the goal is to develop high-performance lead-free piezoelectric ceramics and facilitate their industrialization.