Research On The Properties Of The PMN-PZT Piezoelectric Ceramics Doped With Fe³⁺ And The Optimization Of Process

The high dielectric loss constant, about 3% and low curie temperature of pure PMN-PZT piezoelectric ceramic limit its applications. To solve the problems, firstly, the effects of Fe₂O₃- doping and the doping style on the properties like piezoelectric coefficients d33, relative dielectric constant ? T33 ?0, electromechanical coupling factor kp, dielectric loss constant tg , and curie temperature Tc of 0.2PMN-0.8PZT were investigated. SEM and XRD were used to research the microstructure and phase transition. The datum indicated that 0.2PMN-0.8PZT had wide sinter temperature, about 100℃. At low Fe₂O₃-doping content like 0- 1.0wt%, the d33 and tgδdecreased, Qm increased as the amount of Fe₂O₃-doping, which showed that Fe₂O₃ was a hard dopant. Meanwhile, doping resulted the Tc increasing. The optimum doping content was 1.5wt%, at which doping content, the Fe₂O₃ had the characterize of both soft and hard dopant. In addition, Fe₂O₃ had the effect on the sinter temperature and could increase the ? T33 ?0 and decrease the tgδto half. The influences of different doping styles on the properties of 0.2PMN-0.8PZT were basically the same. When the Zr/Ti ratio equaled 51/49, 0.2PMN-0.8PZT+1.5wt%Fe₂O₃ ceramic was just at the MPB, at which point the performance reached the optimum, d33=253 pC/N, kp=0.514, ? T33 ?0=1975, tg =0.009, Tc=281℃when sintered at 1210℃. Based on the bad performance of 0.2PMN-0.8PZT, the effect of the method of synthesizing, synthesizing temperature and composition were studied. As a result, the one-step synthesizing method was better than the two-step in our lab condition. For the two-step method, preparing the MgNb2O6 in advance and then adding ZrO₂, TiO₂, Pb3O4 to form the PMN-PZT at the second step had better effect than at the first step to form MgNb2O6 adding ZrO₂, TiO₂ and at the second step adding Pb3O4 to form the PMN-PZT. What's more, in the second step, for the synthesizing temperature, 850℃was better than 900℃. Besides, for the one-step method, the piezoelectric property of ceramic pre-sintered at the temperature, 850℃was more excellent than that at 900℃. At the same time, the d33 and ? T33 ?0of 0.25PMN-0.75PZT were higher than those of 0.2PMN-0.8PZT.