Large electrostrains with high temperature stability and low hysteresis are essential for applications in high-precision actuator devices. However, achieving simultaneously all three of the aforementioned features in ferroelectric ceramics remains a considerable challenge. In this work, we firstly report a high unipolar electrostrain (0.12% at 60 kV/cm) in (1–x)NaNbO₃-x[(Ba_0.85Ca_0.15)(Zr_0.1Ti_0.9)O₃] (NN-xBCZT) ferroelectric polycrystalline ceramics with excellent thermal stability (variation less than 10% in the temperature range of 30–160 ℃) and ultra-low hysteresis (< 6%). Secondly, the high-field electrostrain response is dominated by the intrinsic electrostrictive effect, which may account for more than 80% of the electrostrain. Furthermore, due to the thermal stability of the polarization in the pure tetragonal phase, the large electrostrain demonstrates extraordinarily high stability from room temperature to 140 ℃. Finally, in-situ piezoelectric force microscopy reveals ultra-highly stable domain structures, which also guarantee the thermal stability of the electrostrain in (NN-xBCZT ferroelectrics ceramics. This study not only clarifies the origin of thermally stable electrostrain in NN-xBCZT ferroelectric perovskite in terms of electrostrictive effect, but also provides ideas for developing applicable ferroelectric ceramic materials used in actuator devices with excellent thermal stability.

Lead-free ceramics with both high piezoelectric response and good temperature stability are urgently demanded for electromechanical conversion devices. Unfortunately, owing to coexistence of polymorphic phases near room temperature (RT), enhanced piezoelectric properties were usually achieved with occurrence of strong temperature dependence in modified BaTiO₃ (BT)-based ceramics. In this work, we demonstrate that tailoring grain orientations of tetragonal BT-based ceramics can effectively produce substantially enhanced and thermally stabilized piezoelectric response. Both <001>_c- and <111>_c-oriented tetragonal (Ba_0.85Ca_0.15) (Zr_0.05Ti_0.95)O₃ (BCZT) ceramics with texture degrees F>90% were synthesized via templated grain growth. Interestingly, the ceramics textured along the <001>_c polar axis show much higher microscopic and macroscopic piezoelectric properties than those with nonpolar <111>_c texture, indicating an “extender” ferroelectricity nature. Compared with randomly oriented samples, the <001>_c-oriented ceramics exhibit simultaneously ~1.6 times higher piezoelectric strain d₃₃* (~760 pm/V), 4.4 times higher piezoelectric figure of merit d₃₃×g₃₃ (8.8 × 10⁻¹² m²/N), and better temperature stability (strain variation ≤5% between RT and 110 °C). Such thermally stabilized strain response can be mainly attributed to wide temperature range of tetragonal phase and stable domain structure. This work provides a promising route for further developing lead-free piezoceramics with high and temperature-insensitive performance, which can greatly broaden their application areas.