Realization of excellent piezoelectricity and high Curie temperature in BF-BT ceramics via structural regulation and domain engineering

BiFeO₃-BaTiO₃ (BF-BT) is one of the lead-free piezoceramic materials with high Curie temperature (T_C) and high polarization. Herein, the (Bi_0.5Li_0.5Ti)⁶⁺ (BLT) group elements are introduced into the 0.75BiFeO₃-0.25BaTiO₃ (0.75BF-0.25BT) system to optimize comprehensive performances via optimize the intrinsic piezoelectric contribution and the extrinsic piezoelectric contribution. For intrinsic piezoelectric contribution, the tetragonal phase ratio of the ceramics is increased. For extrinsic piezoelectric contribution, the grain structures as well as the domain structures of the ceramics are improved with a relaxor state in which small-sized domains and large-sized domains coexist. The best overall performances are obtained at x = 0.010 with piezoelectric constant d₃₃ ~ 130 pC/N at room temperature, d₃₃ ~ 231 pC/N at 313 ℃, resistance ρ ~ 1.49 × 10⁶ Ω·cm at 300 ℃, Curie temperature T_C ~ 632 ℃ improved significantly. Moreover, when x = 0.010, the piezoelectric thermal stability is also significantly improved, with Δd₃₃ being less than 15% before 200℃, and maintaining 60% of d₃₃ at 400℃. The present experiments provide a new strategy to investigate the origin of the enhanced piezoelectric response of BF-BT ceramics as well as for their applications in the field of high temperature lead-free piezoelectricity.