Remarkably High-Temperature Stability of Bi(Fe1−xAlx)O3BaTiO3 Solid Solution with Near-Zero Temperature Coefficient of Piezoelectric Properties


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The 0.72Bi(Fe1−xAlx)O3–0.28BaTiO3 (= 0, 0.01, 0.03, 0.05, and 0.07, abbreviated as BFAxBT) 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 BFAx–BT ceramics evolve from rhombohedral structure with x < 0.01 to the coexistence of rhombohedral structure and pseudocubic phases with ≈ 0.01, finally to pseudocubic phases when x > 0.03. Remarkably high-temperature stability with near-zero temperature coefficient of piezoelectric properties (TCkp), together with improved piezoelectric properties has been achieved for = 0.01 BFAx–BT ceramics. The BFAx–BT(= 0.01) ceramics simultaneously show the excellent piezoelectric properties of d33 = 151 pC/N, kp = 0.31 and super-high-temperature stability of Td = 420°C, TCkp = 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 TCkp value and the pseudocubic phases possess a negative TCkp value. Thus, the TCkp value of BFAx–BT ceramics can be tuned by composition of x.