Piezoelectric and dielectric properties of 0.05Pb(Al_.0.5Nb _0.5)O₃-0.95Pb(Zr_0.52Ti_0.48)O ₃ ceramics doped with Nb₂O₅ and MnO₂

The solid solution system of 0.05Pb(Al_.0.5Nb_0.5) O₃-0.95Pb(Zr_0.52Ti_0.48)O₃ (PAN-PZT) has been studied for the piezoelectric ultrasonic motor with its high T _c. In this article, we doped the Nb₂O₅ and MnO₂ into the 0.05PAN-0.95PZT ceramics as donor and acceptor respectively and reported the doping effect on the piezoelectric properties, Apparently, Nb₂O₅ induced the "soft" piezoelectric characteristics. However, as Nb₂O₅ also affected the sintered density, which is closely related with the piezoelectric properties, it is quite difficult to identify the role of Nb₂O ₅, which might act as the "donor" and/or sintering enhancer. The optimized piezoelectric properties were obtained d₃₃ = 430 pC/N, k_p = 59%, Q_m = 79, and ε₃ ^T/ε₀ = 1690, when PAN-PZT + 0.7 wt % Nb ₂O₅ sintered at 1200°C for 1 h. When MnO₂ was doped, Mn⁴⁺ ions induced the distortion of perovskite structure and Tc shifted to lower temperature. In addition, d₃₃ and k _p decreased and Q_m dramatically increased with the addition of MnO₂. From these results, it was believed that MnO ₂ mainly acted as acceptor in PAN-PZT ceramics. The optimized piezoelectric properties were obtained d₃₃ = 340 pC/N, k_p = 61.6%, Q_m = 1725, T_c = 392°C, and ε₃^T/ε₀ = 1250, when PAN-PZT + 0.7 wt % Nb₂O₅ with 0.5 wt % MnO₂ ceramics sintered at 1200 °C for 1 h.