Middle-low temperature sintering and piezoelectric properties of CuO and Bi2O3 doped PMS-PZT based ceramics for ultrasonic motors

A ternary solid-solution piezoelectric ceramic of rare-earth oxides modified 0.03 Pb(Mn_1/3Sb_2/3)O₃-0.97 Pb(Zr_0.505Ti_0.495)O₃ + x wt.% CuO + y wt.% Bi₂O₃ (PMS-PZT + x wt.% CuO + y wt. % Bi₂O₃) (x, y = 0–0.2) was successfully prepared via a transient-liquid-phase sintering. Both Cu²⁺ and Bi³⁺ were believed to replace the A-site Pb ions and to evidently induce the lattice shrinkage and the distortion decrease. However, the addition of only a small amount of CuO was found to effectively reduce the sintering temperature, sustain good piezoelectric properties and predominant transgranular fracture modes, but obviously increase the average grain size and high-field dielectric loss. Further experimental results indicate that the grain growth of the ceramics was inhibited effectively and the high-field dielectric loss was reduced through CuO and Bi₂O₃ co-doping. The 0.05 wt% CuO and 0.15 wt% Bi₂O₃ co-doped PMS-PZT ceramics sintered at 1050 °C exhibit excellent dielectric and piezoelectric properties of d₃₃ = 410 pC/N, k_p = 0.62, Q_m = 1478, ε_r = 1550, tan δ = 0.8% (400 V/mm) and T_c = 330 °C. The experimental results can provide a solid fundament for multilayer piezoelectric actuating devices.