Effect of Stress on the Phase Transition and Optimizing Electric-Induced Strain Behavior of Bi0.5Na0.5TiO3-SrTiO3 Lead-Free Co-Fired Multilayer Piezoactuators

A series of (1-x)Bi1/2Na1/2TiO3-xSrTiO3+0.05 wt% MnO2 lead-free multilayer piezoactuators was prepared using a tape casting method, and the field-induced strain performance, temperature stability, electric fatigue and load characteristics were evaluated to assess potential practical applications. In contrast to traditional PZT ceramics, the fabrication of BNT bulk ceramics into multilayer piezoactuators provides significantly decreased strain (S)electric field (E) characteristics as a result of internal compressive residual stress. The inactive edge distance, sintering temperature and layer thickness were all found to affect the compressive residual stress of the actuator. Through reconstructing the material composition and structure of BNT-ST actuators, active strain (0.168 %, 2 kV/mm), total strain (>0.15 %, E <= 2.5 kV/mm) and blocking stress (42.6 MPa) were realized in BNT-based cofired multilayer actuators, displaying a better performance than commercial PZT actuators. These results indicate that environmental-friendly BNT-based lead-free multilayer piezoactuators are promising candidates with regard to practical applications.