Enhanced piezoelectric performance of Cr/Ta non-equivalent co-doped Bi₄Ti₃O₁₂-based high-temperature piezoceramics

In this study, (Cr_1/3/Ta_2/3) 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 Bi₄Ti_3−x(Cr_1/3Ta_2/3)_xO₁₂ (x = 0–0.04) 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 electrical properties due to a decrease in oxygen vacancy concentration. Bi₄Ti_2.97(Cr_1/3Ta_2/3)_0.03O₁₂ ceramics exhibit a high piezoelectric coefficient (d₃₃ = 26 pC·N⁻¹) and a high Curie temperature (T_C = 687 ℃). Moreover, the 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.