Enhancement in multiferroic and piezoelectric properties of BiFeO₃-BaTiO₃-Bi_0.5Na_0.5TiO₃lead-free ceramics with MnO₂addition by optimizing sintering temperature and dwell time

Multiferroic ceramics of 0.705BiFeO3-0.275BaTiO3-0.02Bi0.5Na0.5TiO3+ 1 mol% MnO2were prepared by a conventional ceramic technique and the effects of sintering temperature (Ts) and dwell time (ts) on the phase structure, piezoelectric and multiferroic properties of the ceramics were investigated. As Tsincreases from 880 °C to 1040 °C, the ceramics are transformed from rhombohedral to tetragonal structure and a MPB is formed at Ts= 1000 °C and ts= 2 h. The increase in Tsgreatly improves the densification, electric insulation, ferroelectricity and piezoelectricity of the ceramics, while relatively weak dependences on tsare observed. As Tsincreases from 880 °C to 1000 °C, the magnetism of the ceramics is significantly enhanced and the values of Mrare increased by ∼400%. The optimum sintering conditions of the ceramic is 1000 °C/2 h, in which high density, good electric insulation and enhanced ferroelectricity (Pr= 18.4 μC/cm2), piezoelectricity (d33= 140 pC/N, kp= 31.4%) and ferromagnetism (Mr= 0.099 emu/g) are simultaneously obtained.