Remarkably High‐Temperature Stability of <scp> <scp>Bi</scp> </scp> ( <scp> <scp>Fe</scp> </scp> _{1− <i>x</i>} <scp> <scp>Al</scp> </scp> _<i>x</i> ) <scp> <scp>O</scp> </scp> ₃ – <scp> <scp>BaTiO</scp> </scp> ₃ Solid Solution with Near‐Zero Temperature Coefficient of Piezoelectric Properties

Abstract

The 0.72 Bi ( Fe 1− x Al x ) O 3 –0.28 BaTiO 3 ( x = 0, 0.01, 0.03, 0.05, and 0.07, abbreviated as BFA x – BT ) lead‐free high‐temperature ceramics were prepared by the conventional ceramic processing. Systematic investigation on the microstructures, crystalline structures, dielectric and piezoelectric properties, and high‐temperature stability of piezoelectric properties was carried out. The crystalline structures of BFA x – BT ceramics evolve from rhombohedral structure with x &lt; 0.01 to the coexistence of rhombohedral structure and pseudocubic phases with x ≈ 0.01, finally to pseudocubic phases when x &gt; 0.03. Remarkably high‐temperature stability with near‐zero temperature coefficient of piezoelectric properties ( TCk p ), together with improved piezoelectric properties has been achieved for x = 0.01 BFA x – BT ceramics. The BFA x – BT ( x = 0.01) ceramics simultaneously show the excellent piezoelectric properties of d 33 = 151 pC/N, k p = 0.31 and super‐high‐temperature stability of T d = 420°C, TCk p = 1 × 10 −4 . It is considered that the observed strong piezoelectricity and remarkably high‐temperature stability should be ascribed to the phase coexistence of rhombohedral and pseudocubic phases. The rhombohedral phases have a positive TCk p value and the pseudocubic phases possess a negative TCk p value. Thus, the TCk p value of BFA x – BT ceramics can be tuned by composition of x .