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

ABSTRACT BiFeO _3– BaTiO ₃ (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– 0.34BaTiO ₃ –0.002(Bi _0.5 Li _0.5 )TiO _3– x BiGaO ₃ –0.0035MnO ₂ is designed, namely BF34BT– x BiGaO ₃ (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.