Improved chemical defects, domain structure and electrical properties of BiFeO3-BaTiO3 lead-free ceramics by simultaneous Na/Bi codoping and quenching process

Lead-free piezoelectric 0.7BiFeO3-0.3Ba1-x(Bi0.5Na0.5)xTiO3 (BF-B(BN)xT, 0.00 <= x <= 0.02) ceramics were synthesized with a solid-state reaction method utilizing modified air quenching. The impacts of Na/Bi codoping and air quenching on the structure, defects, and electrical properties of BF-B(BN)xT were investigated. Each sample exhibited a pure perovskite structure with rhombohedral (R) and pseudocubic (pC) phase coexistence. The insulation and piezoelectric properties were improved by appropriate Na/Bi codoping. Due to the enhanced lattice distortion and long parallel strip domains induced by the quenching treatment, excellent piezoelectric performance d33 = 196 pC/N and a high Curie temperature Tc = 498 degrees C were obtained for the quenched BF-B (BN)0.015T ceramic. In addition, in situ measurements of the electromechanical coupling factor (kp) and thermal depolarization studies demonstrated that quenching treatment improved the stability of high-temperature piezoelectric properties, and the d33 of the quenched BF-B(BN)0.015T ceramic remained at 183 pC/N at 400 degrees C, indicating good potential in high-temperature applications.