Low-temperature sintering and piezoelectric properties of ZnO-added 0.41Pb(Ni_1/3 Nb_2/3)O₃-0.36PbTiO₃-0.23PbZrO₃ ceramics

The structure of 0.41(PbNi_1/3Nb_2/3)O₃-0.36PbTiO₃-0.23 PbZrO₃ (0.41PNN-0.36PT-0.23PZ) ceramics changed from pseudocubic to tetragonal when ZnO was added. For the specimens sintered above 1000°C, bulk density slightly decreased with the addition of ZnO but it significantly increased for the specimens sintered below 1000°C. Curie temperature (T_c) and maximum dielectric constant increased when ZnO was added. Coercive electric field (E_c) and mechanical quality factor (Q_m) increased with the addition of ZnO but piezoelectric constant (d₃₃), electromechanical coupling factor (k_p) and dielectric constant (ε₃^T/ε₀) decreased with the addition of ZnO for the specimens sintered above 1,000°C. However, for the specimens sintered below 1000°C, the addition of ZnO significantly improved the piezoelectric and dielectric constants, which could be due to the improvement of bulk density. The good dielectric and piezoelectric properties of d₃₃ = 525 (pC/N), k_p = 0.53 and ε₃^T/ε_o = 3400 were obtained for the specimen with 3 mol% ZnO sintered at 950°C for 1 h.