Bi compensation and poling process to enhance piezoelectric properties of BiFeO₃-BaTiO₃ lead-free piezoceramics

BiFeO₃-BaTiO₃ (BF-BT) ceramics are an excellent choice for high-temperature lead-free piezoelectric ceramic due to their high Curie temperature and good piezoelectric properties, but the volatilization of Bi leads to the formation of A-site cationic vacancies and oxygen vacancies, culminating in heightened leakage currents and detrimental effects on piezoelectric properties. In this study, a chemical composition of 0.70Bi_(1+x)Fe_0·97Al_0·03O₃-0.30BaTiO₃ ceramics, abbreviated as B_1+xFA-BT, where 0 ≤ x ≤ 0.05, were synthesized, with special attention on the effects of Bi compensation and poling process on their insulation and piezoelectric properties. Due to the coexistence of R-PC phases and low leakage current, B_1+xFA-BT ceramics exhibit excellent piezoelectric properties and high Curie temperature, among which the B_1.02FA-BT ceramic boasts optimal overall properties: d₃₃ = 196 pC N⁻¹, T_C = 480 °C, k_p = 34%, θ_max = 49.5° and Q_m = 32, under optimal poling parameters E_p = 50 kV cm⁻¹ and T_p = 100 °C. The poling process is directly linked to the reorientation of domains, the redistribution of positive/negative space charge and the aggregation or injection of holes, which is achieved by tuning the poling field and temperature in a ceramic with optimal integrated piezoelectric properties. The poling process of BF-BT ceramics is significantly influenced by their leakage characteristics, which can have a significant impact on their overall performance. Optimizing electrical poling conditions and minimizing leakage current is crucial to achieving favorable piezoelectric properties in BF-BT ceramics with R-PC coexisting structures.