Multiscale Regulation of BiFeO3-BaTiO3 Lead-Free Ferroelectric Ceramics for Ultrahigh Piezoelectric Performance and Temperature Stability

BiFeO 3 -BaTiO 3 system is considered a promising lead-free candidate for piezoelectric actuators, sensors, and energy-harvesting devices due to its good piezoelectric properties and high Curie temperature. However, achieving synergistic optimization of piezoelectric performance and thermal stability has remained a persistent challenge. Here, we propose a multiscale modulation strategy by precisely controlling Bi excess ( x ) and designing quenching pathways in 0.7Bi (1+ x ) Fe 0.99 Nb 0.01 O 3 -0.3BaTiO 3 ceramics. The results demonstrate that water quenching for sintering in O 2 (O 2 WQ) effectively increases c /a ratio of tetragonal phase and modulates domain configuration and suppressing the concentration of point defects. Bi excess-induced octahedral distortion and valence state modulation of Fe promote the switching of ferroelectric domains. Both enhance piezoelectricity and temperature stability. Remarkably, the x = 0.01 composition with O 2 WQ treatment achieves optimal performance: a room-temperature piezoelectric coefficient d 33 = 236 pC/N, a high Curie temperature T C = 472 °C, an excellent thermal stability across 60-270 °C ( d 33 = 314 ± 47 pC/N), as well as high DC resistivity ρ > 10 6 Ohm·cm at 270 °C. This performance surpasses most reported lead-free piezoelectric systems and confirms the efficacy of our multiscale modulation strategy. This work provides a viable design paradigm for high-performance lead-free piezoelectric ceramics suitable for high-temperature and high-power applications.