Enhanced insulating and piezoelectric properties of 0.7BiFeO3–0.3BaTiO3 lead-free ceramics by optimizing calcination temperature: analysis of Bi3+ volatilization and phase structures

Abstract

Herein, we report the significantly enhanced insulating and piezoelectric properties of a lead-free ceramic in a simple composition of 0.7BiFeO₃–0.3BaTiO₃ (0.7BF–0.3BT) without any addition of MnO₂ or other dopants, which is derived by fine-tuning the calcination temperature (T_cal = 760 °C, 780 °C, 800 °C, 820 °C and 850 °C). All the calcined powders have a main perovskite phase with R3c symmetry and a small amount of Bi₂₅FeO₄₀ impurity, whose ceramics become a typical R3m and PC coexisting structure at 760 °C ≤ T_cal ≤ 820 °C, and a single PC phase at T_cal = 850 °C. T_cal is crucial to optimize the volatilization, density and phase structure including perovskite symmetry and impurity phase, thereby enhancing the insulating properties and piezoelectric properties. Benefitting from weak Bi³⁺ volatilization, low number of , a dense microstructure and appropriate C_R/C_PC ratio at T_cal = 800 °C, the enhanced insulating and piezoelectric properties of 0.7BF–0.3BT lead-free ceramics are achieved, whose d₃₃ = 210 pC N⁻¹, k_p = 0.34, T_C = 507 °C, P_r = 40.6 μC cm⁻², and E_C = 16.4 kV cm⁻¹.