Deciphering the Structure and Electrical Properties of Ce/W Co‐Doped CaBi ₄ Ti ₄ O ₁₅ High‐ T _C Ferro‐/Piezoelectric Materials

ABSTRACT 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 Ce ⁴⁺ and W ⁶⁺ into CaBi ₄ Ti ₄ O ₁₅ (CBT). A series of ceramics with nominal compositions of CaCe _x Bi _{4‒ x} Ti _3.97 W _0.03 O _{(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 Ce ⁴⁺ for Bi ³⁺ 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 ( d ₃₃ ) of 16.5 pC/N, a superior thermal stability of d ₃₃ (retaining 93.5% at 600°C), and an improved resistivity (∼10 ⁷ 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.