Phase structure and electrical properties of (1-x)Bi_1+yFeO₃-xBaTiO₃ lead-free ceramics with different Bi contents

In this work, (1-x)Bi_1+yFeO₃-xBaTiO₃ (x = 0.25, 0.30, 0.35, 0.40; y = − 0.02, 0.00, 0.02, 0.04) ceramics were prepared via the solid-state reaction method. The effects of BaTiO₃ doping and different Bi contents on the phase structure, microstructure, and electrical properties of the ceramics was investigated. Compared with pure BiFeO₃, doping with BaTiO₃ can significantly improve the electrical properties of the ceramics through affecting the phase structure. It is found that the phase structure undergoes a transition from a rhombohedral to a pseudo-cubic phase as x increases. The ceramics with x = 0.30 can be considered as a morphotropic phase boundary, where the rhombohedral and pseudo-cubic phases coexist; furthermore, their electrical performance was improved (P_r = 23.9 µC/cm², E_C = 28.5 kV/cm, \({d}_{33}^{*}\) = 237 pm/V, T_C = 419 °C). Bi excess can improve the dielectric performance of the ceramics at high temperature; however, a severe deficiency of Bi can induce a change in the structure from a mixed phase to a rhombohedral phase where an impurity phase is produced, thus reducing the ceramics performance.