Microstructure and electric property of (1−x)CaBi₄Ti₄O₁₅−xBi₄Ti₃O₁₂ ceramics with high-Curie temperature

High-Curie temperature complex piezoelectric ceramics (1 − x)CaBi₄Ti₄O₁₅−xBi₄Ti₃O₁₂ (short for (1 − x)CBT–xBIT) were fabricated by a solid-state reaction method. The evolution of the crystal structure and the electric property of (1 −x)CBT–xBIT ceramics were investigated. (1  − x)CBT–xBIT had an orthorhombic structure, and no impurity phases existed in. With the addition of BIT, the "CBT part" of 0.9CBT–0.1BIT ceramic had larger crystal structure distortion than CBT ceramics, especially the tilt from the c axis of the TiO₆ octahedron layers. The crystal structure analysis indicated the enhanced octahedral tilt angle is beneficial to the ferroelectricicity of (1 − x)CBT–xBIT ceramics. The residual polarization P_r of (1  − x)CBT–xBIT ceramics (x = 0, 0.1, 1) were 1.97 µC/cm², 6.33 µC/cm² and 2.28 µC/cm², respectively. And, the addition of the "BIT part" increased the concentration of oxygen vacancy and affected the conduction mechanism. Two anomalies (T_m1 and T_m2) existed in the temperature dependence of the dielectric behavior corresponding to the phase transition. Besides, T_m2 and d₃₃ decreased with x increasing and T_m1 did not change markedly. Moreover, 0.9CBT–0.1BIT ceramic obtained the optimal piezoelectric constant (d₃₃ = 15.2 pC/N) and dc resistivity (1.6×10⁵ Ω·cm at 700 °C) compared to that (d₃₃ = 15.2 pC/N, 3.1×10⁴ Ω·cm at 700 °C) of CBT ceramics.