BiAlO₃-modified BiFeO₃-BaTiO₃ high Curie temperature leadfree piezoelectric ceramics with enhanced performance

BiFeO3-BaTiO3 (BF-BT) lead-free piezoelectric ceramics have high piezoelectricity and high Curie temperature (TC), but the mixed-valence Fe ions and Bi3+ volatilization would promote the formation of Bi25FeO40/ Bi2Fe4O9 and oxygen vacancy, which greatly degrade the insulation properties required for polarization. In this study, it was found that the modification of BiAlO3 (BA) in BF-BT ceramics could effectively solve these problems, reducing the leakage current to 1 Chi 9 10(-9) A.cm(-2) and transiting the space charge-limited conduction to ohmic conduction. Because of the enhanced insulation properties and appropriate rhombohedral-pseudocubic phase ratio (C-R/C-PC), BF-BT-(x)BA ceramics in an optimized composition obtain enhanced piezoelectric performance: piezoelectric charge coefficient (d(33)) = 196 pC.N-1, planar electromechanical coupling coefficient (kp) = 31.1%, T-C = 487 degrees C and depolarization temperature (Td) = 250 degrees C; unipolar strain (Suni) = 0.17% and piezoelectric strain coefficient (d33*) = 335 pm.V-1 at 100 degrees C. Especially, d(33) exceeds 283 pC.N-1 at 233 degrees C and d33* is 335 pm.V-1 at 100 degrees C, showing an excellent high-temperature piezoelectricity and high depolarization temperature. The results are attributed to the domain structure of rhombohedral-pseudocubic phase coexistence and its high-temperature switching behavior. This work provides a feasible and effective approach to improve the high temperature piezoelectric properties of BF-BT-xBA ceramics, making them more suitable for high temperature applications.