Concurrent Enhancement of Piezoelectricity and Curie Temperature in Bi ₄ Ti ₃ O ₁₂ Ceramics via Dual‐Modification

ABSTRACT The inherent structural anisotropy of bismuth layer‐structured ferroelectrics has long hindered the simultaneous improvement of piezoelectric activity and thermal stability. In this work, we introduce a dual‐modification approach—combining Cr/Ta aliovalent co‐doping with hot‐press sintering—to overcome this challenge in Bi ₄ Ti ₃ O ₁₂ (BIT) ceramics. The optimized ceramics exhibit a record‐high piezoelectric coefficient ( d ₃₃ ) of 44 pC N ⁻¹ together with a remarkably high Curie temperature ( T _C ) of 690°C. Furthermore, the ceramics retain excellent thermal stability, maintaining d ₃₃ = 38 pC N ⁻¹ after annealing at 650°C, along with high electrical resistivity (8.7 × 10 ⁶ Ω cm at 500°C) and low dielectric loss (tan δ = 1.6% at 500°C). Multi‐scale structural analyses reveal that the synergistic modification induces dense microstructures and nanoscale ferroelectric domains with preferred grain orientation, which facilitate efficient domain switching and underpin the superior functional performance. This study demonstrates a viable strategy for designing high‐temperature, lead‐free piezoelectrics, opening pathways toward reliable operation in extreme environments.