Excellent High‐Temperature Piezoelectric Response of BiFeO _3– BaTiO ₃ Piezoceramics Achieved Through Phase Boundary and Nanodomain Morphology Engineering

BiFeO_3-BaTiO₃ (BF-BT) ceramics are widely regarded as one of the most promising candidates among lead-free piezoelectric materials. Although lead-free piezoelectric ceramics have significant application prospects in brakes and sensors, they still face considerable challenges when used at high temperatures. In this work, a new type of 0.66BiFeO_3-0.34BaTiO₃-0.002(Bi_0.5Li_0.5)TiO_3-xBiGaO₃-0.0035MnO₂ is designed, namely BF34BT-xBiGaO₃ (BG). The piezoelectric coefficient d_33max of the BF34BT-0.005BG ceramic is 795.8 pC/N at a real-time depolarization temperature of T_dr = 341.9°C. The results show that the main reason for obtaining such an excellent high-temperature piezoelectric response is the incorporation of Ga, which leads to the coexistence of rhombohedral and tetragonal phases. Furthermore, the BF34BT-0.005BG ceramic possesses a composite nanodomains morphology and polar nanoregions. Additionally, the atomic-level structural characteristics of the BF34BT-0.005BG ceramic are characterized via high-resolution transmission electron microscopy and scanning transmission electron microscopy. This breakthrough will contribute to a more comprehensive understanding of the structural characteristics of ferroelectric domains in BF-BT piezoelectric ceramics and will provide an important reference for the future development of ultrahigh-performance BF-BT piezoelectric ceramics through phase boundary and nanodomain morphology engineering.