Concurrently Enhanced Piezoelectric Performance and Curie Temperature in Stressed Lead-free BCTZ Ceramics

Eco-friendly, lead-free BaTiO₃-based piezoelectric materials play a crucial role in advancing sustainable electronic applications. Improving piezoelectric properties in lead-free piezoelectric ceramics often involves a trade-off with Curie temperature (T_C) due to various performance metrics. In this study, we implemented an innovative stress engineering approach by introducing a secondary phase BaAl₂O₄. This method simultaneously enhances both T_C and the piezoelectric coefficient (d₃₃) in (Ba_0.85Ca_0.15)(Ti_0.9Zr_0.1)O₃ (BCTZ) ceramics. The difference in thermal expansion coefficients between BCTZ and BaAl₂O₄ induces internal stress within the BCTZ matrix, leading to significant lattice distortion and altering the phase fractions of BCTZ, which improves both T_C and the d₃₃. Additionally, the local electric field at the interface of BCTZ and BaAl₂O₄, along with the incorporation of Al³⁺ in ABO₃ lattice, contribute to the enhanced d₃₃. Notably, the optimized BCTZ ceramics exhibit an exceptionally high d₃₃ of 650 ± 16 pC N⁻¹, d₃₃^* of 1070 pm V⁻¹, and T_C of 96.5 ± 1.0 ^oC, placing it at the forefront of lead-free BT-based piezoelectric materials. 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 a wide range of temperature applications.