Deciphering the Structure and Electrical Properties of Ce/W Co-Doped CaBi₄Ti₄O₁₅ High-T_C Ferro-/Piezoelectric Materials

Bismuth layer-structured ferroelectrics (BLSFs) are promising for high-temperature piezoelectric sensing but are limited by their low piezoelectric coefficient and poor resistivity at elevated temperatures. This work addresses these challenges by co-doping small-radius, high-valence cations of Ce⁴⁺ and W⁶⁺ into CaBi₄Ti₄O₁₅ (CBT). A series of ceramics with nominal compositions of CaCe_xBi_4‒xTi_3.97W_0.03O_(15.03+x/2) (0 ≤ x ≤ 0.12) were synthesized by the conventional solid-state reaction method, and the structure and electrical properties of the materials were systematically investigated. X-ray diffraction and Raman spectroscopy analysis confirmed that substitution of Ce⁴⁺ for Bi³⁺ at the A-site increases the tilting of oxygen octahedra and enhances the disparity in the Ti–O bond lengths. This structural evolution, along with a reduction in oxygen vacancies due to the nature of donor doping, contributed to a significant improvement in the ferroelectric and piezoelectric properties of CBT. The optimal composition with x = 0.08 (CCBTW-8) exhibited an improved piezoelectric coefficient (d₃₃) of 16.5 pC/N, a superior thermal stability of d₃₃ (retaining 93.5% at 600°C), and an improved resistivity (∼10⁷ Ω·cm at 500°C). This study provides an effective approach for designing BLSFs with enhanced electrical properties, thereby improving their potential for practical applications in elevated temperature environments.