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

Abstract

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 °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 °C, indicating good potential in high-temperature applications.