Low sintering temperature, large strain and reduced strain hysteresis of BiFeO₃–BaTiO₃ ceramics for piezoelectric multilayer actuator applications

BiFeO₃–BaTiO₃ solid solutions with pseudo-cubic phase have received a lot of attention because of their large strain for potential piezoelectric multilayer actuator applications. However, the high sintering temperature, large dielectric loss and severe strain hysteresis hindered their real applications. In this work, Li₂CO₃ sintering aid modified 0.64BiFeO₃-0.36BaTiO₃ (BF-BT-L) ceramics were prepared by the high-temperature sintering method, and their phase structure, microstructure, electric properties as well as strain were investigated. With the increase of Li₂CO₃ content, the sintering temperature decreases down to 900 °C, and the relative density increases up to 96%. Of particular importance is that the dielectric loss and strain hysteresis of BF-BT-L ceramics are reduced by 40% and 47%, respectively, while BF-BT-L ceramics shows a large strain of 0.3% (60 kV/cm). The sintering temperature, relative density, strain, large-signal d₃₃* and strain hysteresis of BF-BT-L ceramics are 900 °C, 96.5%, 0.3%, 500 pm/V, and 25% respectively. The reduced dielectric loss and strain hysteresis result from the enhanced relative density, decreased concentration of defects and partial phase transition from partial pseudo-cubic to rhombohedral one by Li₂CO₃ additions. Furthermore, BF-BT-L ceramics show positive temperature dependent strain, with large d₃₃* and strain hysteresis of 675 pm/V and 15% at 200 °C respectively. The simple composition, low sintering temperature, large strain and reduced strain hysteresis of BF-BT-L ceramics indicate that they are promising candidates for high-performance and lead-free piezoelectric multilayer actuator applications.