Enhanced insulating and piezoelectric properties of 0.7BiFeO(3)-0.3BaTiO(3) lead-free ceramics by optimizing calcination temperature: analysis of Bi3+ volatilization and phase structures

Herein, we report the significantly enhanced insulating and piezoelectric properties of a lead-free ceramic in a simple composition of 0.7BiFeO(3)-0.3BaTiO(3) (0.7BF-0.3BT) without any addition of MnO2 or other dopants, which is derived by fine-tuning the calcination temperature (T-cal = 760 degrees C, 780 degrees C, 800 degrees C, 820 degrees C and 850 degrees 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 degrees C <= T-cal <= 820 degrees C, and a single PC phase at T-cal = 850 degrees 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 v(o)(center dot center dot), a dense microstructure and appropriate C-R/C-PC ratio at T-cal = 800 degrees C, the enhanced insulating and piezoelectric properties of 0.7BF-0.3BT lead-free ceramics are achieved, whose d(33) = 210 pC N-1, k(p) = 0.34, T-C = 507 degrees C, P-r = 40.6 mu C cm(-2), and E-C = 16.4 kV cm(-1).