Optimized comprehensive piezoelectric performances in lead-free BiFeO3-BaTiO3 ceramics via site-selective Sm3+ substitution

Lead-free piezoelectric ceramics with high Curie temperature are urgently demanded to replace toxic lead-based materials for environmental sustainability, among which BiFeO 3 –BaTiO 3 (BF-BT) systems show promising potential. Although chemical substitution is widely adopted to modulate properties, achieving balanced electromechanical performance in BF-BT ceramic remains challenging due to the complexity of A-site cations (Bi 3+ and Ba 2+ ) with different valence states and ionic radii. Herein, we systematically investigated site-selective Sm 3+ substitution effects on structure and properties of BF-BT ceramics. Bi-site substitution promoted grain growth and reduced leakage current via suppressed bismuth volatilization, while Ba-site substitution refined grains but severely disrupted ferroelectric ordering due to charge imbalance. Furthermore, 2/3Bi 0.995 Sm 0.005 FeO 3 -1/3BaTiO 3 (BF-BT-Bi-Sm0.005) achieved optimized comprehensive performance, exhibiting a piezoelectric coefficient of d 33  = 87 pC/N, mechanical quality factor of Q m  = 101.5, Curie temperature of T m  = 394 °C, and low leakage current density. These results demonstrate that low-level Bi-site substitution effectively coordinates defect chemistry, microstructure, and domain engineering to achieve superior electromechanical coupling, providing a rational design strategy for high-performance lead-free ceramics suitable for high-temperature sensing applications.