Achieving high electrostrain performance in BNT‐based lead‐free piezoelectric ceramics modified by Sr(Sn _0.5 Ta _0.4 )O ₃

Abstract Piezoelectric ceramics, renowned for their ability to interconvert mechanical strain/stress and electrical signals, are widely utilized in diverse fields, such as electronic communications, aerospace, and national defense. Their appeal lies in their rapid response, precise motion control, and low power consumption, making them indispensable in advanced electromechanical systems. Bismuth sodium titanate (BNT)‐based ceramic materials exhibit excellent strain performance and piezoelectric response, making them highly promising for applications in actuators and transducers. In this study, the piezoelectric ceramic system of (0.93− x )Bi 0.5 Na 0.5 TiO 3 −0.07BaTiO 3 − x Sr(Sn 0.5 Ta 0.4 )O 3 ( x = 0–0.02, BNBT− x SST) were synthesized using the conventional solid‐state reaction method. Through a combination of composition design and phase boundary engineering, the microstructure of the ceramics is modified, and a systematic analysis of the relationship between the electrical properties and the microstructure is conducted. The results indicate that the addition of SST reduces the domain size and influences the phase evolution, gradually transitioning the ceramics from non‐ergodic relaxor (NR) to ergodic relaxor (ER) state. Among all the compositions, BNBT−0.010SST exhibits outstanding performance. At a relatively low driving electric field ( E = 50 kV/cm), the maximum piezoelectric strain coefficient ( d 33 * ) reaches 632 pm/V, while under a relatively higher driving electric field ( E = 80 kV/cm), a strain response of 0.42% is achieved. This exceptional performance is believed to result from a reversible phase transition between the FE and ER states driven by the electric field. Additionally, the strain of this ceramic remains stable at over 90% within the temperature range of 30°C–100°C, demonstrating outstanding temperature‐insensitive properties. At the same time, compared to other BNT‐based ceramic systems, the hysteresis at room temperature has been effectively reduced, remaining below 47%. Therefore, this study provides valuable insights for improving the strain performance of NBT‐based lead‐free piezoelectric ceramics, offering greater possibilities for their application in piezoelectric devices.