Temperature dependent of thermal expansion and ferroelectric properties for BiAlO3-modified BaTiO3 lead-free ceramics

Perovskite structure (1 − x)BaTiO₃–xBiAlO₃ (BT–xBA, x = 0.05, 0.08 and 0.1, corresponding to BT–5BA, BT–8BA and BT–10BA, respectively) ceramics were prepared by a solid state reaction route. Crystal structure of BT–xBA ceramics was determined by using XRD. Dielectric properties were studied as a function of temperature at different frequencies, which indicated that the phase transition temperature (T_m) decreased with increasing x. With increasing temperature, thermal expansion dl/l increased while thermal expansion coefficient α had weak concentration dependence. The Burns temperature was much higher than the transition temperature T_m for the BT–5BA and BT–10BA ceramics. Polarization hysteresis loops (P–E), electrostrictive (S–E) and S versus P² (S–P²) at different temperatures were displayed. P_max slightly decreased due to thermally activated leakage current, meanwhile, S_max decreased at above T_m with the contribution of ferroelectric domain reorientation decreased. The electrostrictive coefficient Q value was clearly larger than that of lead-based electrostrictors at room temperature. Furthermore, it exhibited a slim loop with negligible hysteresis and a subtle linear feature at higher temperature.