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High oxygen vacancy concentration produced by bismuth volatilization during the sintering process has become one of the most important obstacles for the practical applications of Bi4Ti3O12 (BIT)-based high temperature piezoelectric ceramics. In this work, Cu and Sb were selected to modify the oxygen vacancy concentration and the electrical properties of the BIT ceramic. The crystal structure, microstructure, electrical conduction behaviors, and piezoelectric properties of Bi4Ti3 − x(Cu1/3Sb2/3)xO12 (BTCS) (x = 0, 0.01, 0.02, 0.03, 0.035, 0.04, and 0.05) ceramics were investigated in detail. Codoping significantly reduced the oxygen vacancy concentration and resulted in enhanced electrical resistivity along with improved piezoelectric properties. The BTCS ceramic with x = 0.035 exhibited optimized comprehensive performances such as a remarkable DC resistivity of 1.40 × 107 Ω cm at 500 °C and a relatively large piezoelectric coefficient (24 pC/N). Furthermore, the ceramic also showed good thermal stability of the piezoelectric coefficient and an excellent fatigue behavior. These results demonstrate the great potentials of Cu/Sb codoped BIT ceramics for piezoelectric device applications at high temperatures up to 500 °C.

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Nb self‐doped Bi3Ti1‐xNb1+xO9 (x = 0, 0.02, 0.04, 0.06, 0.08, and 0.1) high‐temperature piezoelectric ceramics were fabricated through the conventional solid‐state sintering method. The effects of different Nb self‐doping levels on the microstructure, piezoelectric activities, and electrical conduction behaviors of these Nb self‐doped Bi3Ti1‐xNb1+xO9 ceramics were studied in detail. Large doping level effects on piezoelectric activity and resistivity were confirmed, which might be ascribed to the evolution of the crystal structure and the variations of the oxygen vacancy concentration and the grain anisotropy induced by Nb doping. An optimized piezoelectric coefficient (d33) of 11.6 pC/N was achieved at x = 0.04 with a Curie temperature of 906°C. Additionally, an improved DC resistivity of 6.18 × 105 Ω·cm at 600°C was acquired in this ceramic. Furthermore, the ceramic exhibited excellent thermal stability with the d33 value maintaining 95% of its initial value after being annealed at 850°C for 2 hours. These results showed that Nb self‐doped Bi3Ti1‐xNb1+xO9 ceramics might have great potentials for high‐temperature piezoelectric applications.

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