Enhanced piezoelectric performance of Cr/Ta non-equivalent co-doped Bi ₄Ti ₃O ₁₂-based high-temperature piezoceramics

In this study, (Cr1/3/Ta2/3) non-equivalent co-doped Bi₄Ti₃O₁₂ (BIT) ceramics were prepared to solve the problem that high piezoelectric performance, high Curie temperature, and high-temperature resistivity could not be achieved simultaneously in BIT-based ceramics. A series of Bi₄Ti3-x(Cr1/3Ta2/3)xO₁₂ (x = 0-0.040) ceramics were synthesized by the solid-state reaction method. The phase structure, microstructure, piezoelectric performance, and conductive mechanism of the samples were systematically investigated. The B-site non-equivalent co-doping strategy combining high-valence Ta⁵⁺ and low-valence Cr³⁺ significantly enhances the electrical properties due to the decrease in oxygen vacancy concentration. Bi₄Ti2.97(Cr1/3Ta2/3)0.03O₁₂ceramic exhibits a high piezoelectric coefficient (d₃₃= 26 pC×N⁻¹) and a high Curie temperature (TC= 687 ℃). Moreover, a significantly increased resistivity (ρ = 2.8×10⁶ Ω·cm at 500 ℃) and good piezoelectric stability up to 600 ℃ are also obtained for this composition. All the results demonstrate that Cr/Ta co-doped BIT-based ceramics have great potential to be applied in high-temperature piezoelectric applications.