Elaborately-designed high-performance BiFeO3-PbTiO3 ceramics through refreshing phase boundary

The development of high-performance BiFeO₃-PbTiO₃ (BF-PT) piezoelectric compositions is highly desirable, but still challenged due to their high Curie temperature (T_c), large lattice distortion and octahedral tilt induced large antiferrodistortion in rhombohedral-tetragonal phase (R3c-P4mm) coexisted compositions. Here, a dual strategy by introducing the pseudo-cubic (Pc) phase in place of the R3c phase, and adjusting the lattice distortion of P4mm phase was realized in 0.60Bi_0.95La_0.05FeO₃-(0.40-x)PbTiO₃-xBaTiO₃, where a large piezoelectric coefficient d₃₃ of ∼410 pC/N, a high T_c of ∼416 °C as well as a good thermal stability can be achieved at x=0.20 composition. The structural analyses indicate that the superior piezoelectric activity should be associated with several factors including the coexistence of tetragonal (T) and Pc phases without octahedral tilt, the field-induced reversible T-Pc transition and the optimized c/a ratio. More pronouncedly, the extrinsic piezoelectric response induced by significantly enhanced domain wall motion contributes to almost ∼70 % of the quasi-static d₃₃ value. Moreover, the robust domain texture up to ∼400 °C is responsible for its good thermal stability. These merits suggest giant potentials of the elaborately-designed composition as high-temperature piezoelectric materials.