Low Temperature Sintering Behavior And Doping Effects Of PZT-PMS-PZN Based High-power Piezoelectric Ceramics

Nowadays, high-power piezoelectric ceramics have received extensive attention and study due to their increasing applications in piezoelectric actuators and transformers. Particularly, the multilayer layer piezoelectric devices become a popular topic for their high power density. In general, co-firing process is preferred for multilayer devices. If the piezoelectric ceramics could be sintered below 900°C, pure Ag internal electrodes can be used instead of Ag-Pd alloy and the volatilization of PbO can be suppressed as well.These days, some ternary or quaternary high-power piezoelectric ceramics were obtained by adding perovskite structure relaxors into PZT system. Among them, PZT–PMS–PZN quaternary system is a most qualified candidate for high-power applications with good electrical properties: d33 = 369 pC/N, Qm = 1381, k_p = 64%, tanδ= 0.44%, andε₃₃^T = 1600. However, previous studies used the molten salt synthesis method and the sintering temperature was as high as 1100°C. Therefore, PZT-PMS-PZN quaternary system was selected in this study, the composition design, low temperature sintering behavior and doping effects were discussed with respect to the crystal structure, micro-morphology and electrical performance.0.90Pb(Zr_xTi_1-xO3-0.05Pb(Mn1/3Sb2/3O3-0.05Pb(Zn1/3Nb2/3)O3 quaternary high power piezoelectric ceramics were synthesized by using conventional solid-state sintering; to decrease the sintering temperature CuO was added as a sintering agent. The crystal structure, micro-morphology and electrical properties were studied in terms of Zr:Ti ratio and CuO content. These results indicate that the Zr:Ti ratio has a significant influence on the electrical properties; 0.90PZT-0.05PMS-0.05PZN (Zr:Ti=48:52) ceramics sintered at 1100°C with maximum tetragonality exhibit the optimal electrical properties: d33 = 355 pC/N, Qm = 1550, kp = 60%, tanδ= 0.33%, andε33^T = 1308. Moreover, 1.0 wt% CuO additive has a significant improvement in the sinterability of 0.90PZT-0.05PMS-0.05PZN ceramics, lowering the sintering temperature to 900°C and maintaining moderate electrical properties: d33 = 306 pC/N, Qm = 997, kp = 53.6%, tanδ= 0.50%, andε33^T = 1351. The low temperature sintering behavior could be explained with the formation of a transient liquid phase by CuO during sintering. Moreover, the endothermic peak at about 930°C in the differential thermal analysis (DTA) curve of the raw ceramic powder provides further evidence for amorphous phase.To obtain more optimum piezoelectric properties, La2O3 and Nb2O5 were selected as donor doping to 0.90PZT-0.05PMS-0.05PZN + 1.0 wt% CuO system. Our study demonstrates that La2O3 is very effective on piezoelectric properties, remarkably increasing the d33 and kp value without degrading the Qm value. Finally, 0.5 wt% La2O3 added 0.90PZT-0.05PMS-0.05PZN + 1.0 wt% CuO ceramics show excellent electrical properties: d33 = 355 pC/N, Qm = 936, kp = 58.4%, tanδ= 0.32%, andε33^T= 1590. On the other hand, the effect of Nb2O5 on piezoelectric properties is much complicated, 0.50 wt% Nb2O5 doped 0.90PZT-0.05PMS-0.05PZN + 1.0 wt% CuO ceramics have a remarkable improvement in kp value and maintain good electrical properties: d33 = 300 pC/N, Qm = 971, kp = 58.4%, tanδ= 0.36%, andε33^T = 1332.</sub>