Enhanced piezoelectric activity with good thermal stability and improved electrical resistivity in Ta–Mn co-doped CaBi₄Ti₄O₁₅ high-temperature piezoceramics

Aurivillius phase CaBi₄Ti_4-x (Ta_2/3Mn_1/3)_xO₁₅ (x = 0–0.1) high-temperature piezoelectric ceramics were fabricated using the conventional solid-state reaction process. The effects of the Ta–Mn co-doping level on the structure, piezoelectric properties and electrical conduction behaviours of the as-prepared CBT (CaBi₄Ti₄O₁₅) ceramics were explored in detail. It was revealed that the Ta–Mn co-doping efficaciously enhanced the electrical performances of the CaBi₄Ti₄O₁₅ ceramic, which may be due to optimisation of the crystal structure and a reduction in the oxygen vacancy concentration. The composition with x = 0.04 presented superior electrical properties with an outstanding piezoelectric constant (d₃₃) of 24 pC/N accompanied by a high Curie temperature (T_C) of 793 °C, an optimised dielectric loss (tanδ) of 1.5%, and an improved resistivity (ρ) of 4.96 × 10⁸ Ω cm at 400 °C. Moreover, the ceramic exhibited impressive thermal stability with the d₃₃ value maintaining 91.7% of its initial value at room temperature (25 °C) after being annealed at 600 °C for 2 h. The improved performance indicates that the Ta–Mn co-doped CaBi₄Ti₄O₁₅ ceramic might be a promising candidate for piezoelectric device applications at elevated temperatures.