Simultaneous enhancement of electro-strain and thermal stability from 40 °C to 120 °C in Nd^3 + -doped BNT-based ceramics

Piezoelectric ceramics, capable of converting electrical energy into mechanical energy, are widely used as actuators. Among lead-free piezoelectric ceramics, sodium bismuth titanate (BNT)-based ceramics have attracted significant attention due to their large strain response under electric fields. Nevertheless, achieving both large strain and wide operational temperature stability remains a critical challenge. In this work, we developed lead-free piezoelectric ceramics with the composition (((Bi_1.03(1-x)Nd_x)_0.5Na_0.5)_0.94Ba_0.06TiO₃, 0 ≤x ≤ 0.06). The incorporation of Nd³⁺ effectively lowers the ferroelectric-relaxor transition temperature (T_FR) and promotes the formation of highly responsive polar nanoregions (PNRs). These field-sensitive PNRs act as active nucleation sites, dramatically accelerating domain switching kinetics. The synergistic interplay of these effects enhances polarization rotation and domain wall motion, ultimately yielding superior macroscopic strain performance. Consequently, the x = 0.04 ceramic exhibits a high electro-strain of 0.33 %. Especially, superior temperature stability is achieved in the above ceramic, as evidenced by strain variation below 15 % across a broad temperature range (40–120 °C), originating from the negative contribution of lattice distortion with increasing temperature and the positive contribution of temperature-enhanced domain switching capability. This work paves the way for the development of high-performance lead-free actuators for applications across a wide temperature range.