Effect of La A-site doping on the electro-induced strain and conductivity mechanism of BiFeO₃-BaTiO₃ lead-free piezoelectric ceramics

The poor electrical properties and high leakage current of BiFeO₃-BaTiO₃-based ceramics are the main reasons that hinder their application. A two-step sintering method prepared the 0.68Bi_1-xLa_x(Fe_99.8%Sb_{0.2 %})O₃-0.32BaTiO₃ ceramics (x = 0, 0.005, 0.01, 0.015, abbreviated as BL_xFS-BT). The surface morphology and properties of the ceramic were observed and tested using different techniques. La ion doping significantly affects the crystal structure, leakage current, and the electro-induced strain of the BL_xFS-BT ceramics. BL_0.005FS-BT ceramics achieve 0.198 % unipolar electro-induced strain and 396 pm/V inverse piezoelectric coefficient under a 50 kV/cm electric field, and they can maintain good temperature stability at high temperatures. A large strain of 0.43 % was obtained at 150 °C. The inhibition effect of La ion on Fe valence and oxygen vacancy formation also greatly improves the insulation performance of ceramics. This work shows that BF-BT-based ceramics via ion substitution defect engineering effectively enhance electrical and insulating properties.