Concurrently enhanced piezoelectric performance and curie temperature in stressed lead-free Ba0.85Ca0.15Ti0.9Zr0.1O3 ceramics

Eco-friendly, lead-free BaTiO₃-based piezoelectrics are critical for sustainable electronics, but improving their piezoelectric properties often compromises Curie temperature (T_C). To address this trade-off, we implemented an innovative stress engineering approach by introducing a secondary phase BaAl₂O₄ in Ba_0.85Ca_0.15Ti_0.9Zr_0.1O₃ (BCTZ) ceramics. The thermal expansion mismatch between BCTZ and BaAl₂O₄ induces internal stress within the BCTZ matrix, causing significant lattice distortion and phase fraction modulation, which improves both T_C and the piezoelectric coefficient (d₃₃). Additionally, the local electric field and Al³⁺ doping in ABO₃ lattice further enhance d₃₃. Optimized BCTZ ceramics achieve d₃₃ of 650 ± 16 pC N^-1, d₃₃^* of 1070 pm V^-1, and T_C of 96.5 ± 1.0 °C, placing them at the forefront of lead-free BaTiO₃-based piezoelectrics. This study underscores the effectiveness of bulk stress engineering via a secondary phase for enhancing lead-free piezoelectric ceramics, paving the way for developing high-performance piezoelectric ceramics suitable for broad temperature applications.