Structure and thermal stability investigations of (1-x)CaBi4Ti4O15-xNa0.5Bi4.5Ti4O15

The successful synthesis of (1-x)CaBi₄Ti₄O₁₅-xNa_0.5Bi_4.5Ti₄O₁₅ (CNBT-x, x = 0, 0.3, 0.5, 0.7, 1) high-temperature piezoelectric ceramics has been accomplished through the utilisation of a conventional solid-state reaction method. The primary focus of our research pertains to the ceramic structure of solid solutions, piezoelectric properties, and ferroelectric characteristics. Adding Na_0.5Bi_4.5Ti₄O₁₅ to CaBi₄Ti₄O₁₅ promotes lattice distortion, inhibits grain growth, reduces oxygen vacancies, and improves the d₃₃ value of CBT. When x = 0.7, the ceramics piezoelectric performance d₃₃ value of 24 pC/N, which is significantly higher than that of conventional CBT ceramics (d₃₃ = 8 pC/N). Furthermore, the Curie temperature (T_C) of this material is 685 °C. The d₃₃ value remains as high as 21 pC/N even after annealing at 600 °C, indicating excellent thermal stability. The incorporation of Na⁺ and Bi³⁺ ions markedly reduced the oxygen vacancy concentration, resulting in resistivities reaching up to 10⁷ Ω cm at 500 °C. Additionally, the material exhibits excellent thermal stability at elevated temperatures and a k_p value charge ranging from 5.2 % to 6 % (less than 16 %) over the temperature range from room temperature to 450 °C. The above properties suggest that CNBT-0.7 ceramics are ideal for use in high-temperature piezoelectric sensors.