Circumventing the Piezoelectric Performance Bottleneck in Bi0.5Na0.5TiO3–Based Ceramics by Designing Multilayer Piezoelectric Ceramics with Local Phase Transition

Abstract Bi0.5Na0.5TiO3-based piezoceramics are attractive for their excellent electrical properties, but their industrial application is constrained by the difficulty in simultaneously achieving a high piezoelectric coefficient (d33 > 300 pC/N), a high ferroelectric-relaxor phase transition temperature (TF–R > 200 °C), and a low d33 variation (<20%). Herein, the aforementioned performance bottleneck is circumvented by designing the multilayer piezoelectric ceramics (MLPC) with a local phase transition from ferroelectric to relaxor state. The local phase transition is achieved by grinding sintered 0.93Bi0.5Na0.5TiO3–0.07BaTiO3 ceramic into a powder and then incorporating it into the 0.85Bi0.5Na0.5TiO3–0.15BaTiO3 ceramic. By this strategy, a five-layer piezoelectric ceramic possesses a high apparent d33 of 480 pC/N and a high TF–R of 220 °C. Furthermore, the d33 variation in the MLPC is less than 17% over the temperature range of 30–170 °C. The excellent temperature stability is associated with an appropriate reduction in remanent polarization, which is primarily attributed to the local temperature-sensitive rhombohedral and tetragonal distortions. These distortions then trigger a local phase transition from the ferroelectric R3c and P4mm phases to the relaxor P4bm phase. This work offers an alternative paradigm for designing high-performance MLPC.