High electromechanical strain properties by the existence of nonergodicity in LiNbO3–modified Bi1/2Na1/2TiO3–SrTiO3 relaxor ceramics

This study investigated the effect of LiNbO₃ modification on the dielectric, ferroelectric and electromechanical strain properties of Bi_1/2Na_1/2TiO₃–SrTiO₃ (BNT–ST) lead–free relaxor ceramics. The sintering temperature for lead–free BNT–ST relaxor ceramics was slightly decreased from 1175?°C to 1050?°C by modifying with LiNbO₃. We found that the sintering temperature affects the dielectric behavior of 0.76BNT–(0.24?x)ST–xLiNbO₃ (BNST–100xLN) ceramics at high temperature (near dielectric maximum temperature, T_m). The T_m for the low–temperature sintered sample was shifted to relatively higher temperature by comparison with the high–temperature sintered samples. Furthermore, the degradation of dielectric behavior near T_m in low–temperature sintered BNST–2LN ceramics was revealed after poling treatment and seem to be related to the existence of a high temperature stabilized nonergodic relaxor phase. Accordingly, we assume that the stabilized nonergodic relaxor phase is responsible for the relatively late transition from ferroelectrics to the relaxor. Therefore, we obtained the improved d₃₃^* of 616?pm/V as the highest value in low–temperature sintered BNST–2LN ceramics.