| According to the required properties of piezoelectric transformer, the possibility of improving mechanical quality factor (Qm), electrical quality factor (Qe\ electromechanical coupling factor (A^) and temperature stability of resonant frequency was analyzed from the aspects of morphotropic phase-boundary (MPB), composite ceramics, acceptor dopants and transient liquid-phase sintering. The rules of designing multi-system ceramics for piezoelectric transformer were proposed and the systems of Pb(Zn1/3NbM)O3-PbZrO3-PbTiO3 (PZN-PZT) and Pb(Mn)/3Nb2/3)O3-Pb(Zn1/3NbM)O3-PbZrO3-PbTiO3 (PMN-PZN-PZT) were designed under the guide of these rules.PZN-PZT and PMN-PZN-PZT ceramics were prepared by the two-step solid-state reaction. The effects of technological parameters (sintering temperature and lead-rich atmosphere), MnO2, CuO addition, PMN relative amount on the phase structure, microstructure, dielectric and piezoelectric properties of the systems of PZN-PZT and PMN-PZN-PZT were investigated systematically. By adjusting the ratio of composition, the piezoelectric ceramics with excellent properties were successfully prepared. Furthermore, the three types of piezoelectric transformers were made and the aging behaviors were studied. The main contents of this paper were listed as follows:At the basis of experimental works and reported literatures, the rules of designing multi-system ceramics for piezoelectric transformer were proposed and the detailed rules were shown as follows: The ceramic composition should have high amount of PbZrO3 and PbTiO3 for the demand of high curie temperature of piezoelectric transformer. In addition, as MPB show strong piezoelectricity, the ceramic composition should be designed close to MPB. However, much attention should be paid that the composition was in tetragonal region near MPB but not on MPB because of the poor repeated piezoelectricity of MPB composition. Moreover, as Qm had close relation with voltage step-up ratio and working stability of piezoelectric transformer, improving Qm was essential, which could be realized with acceptor doping or Pb(Mn1/3NbM)O3, Pb(Mn1/3SbM)03 addition. Furthermore, because the piezoelectric transformer was operated in resonant frequency, the high temperature stability of resonant frequency was necessary. Designing composite ceramics or adding stabilized dopants of SrCO3, BaCO3, La2O3 et al was feasible. Piezoelectric transformer also need high dielectric constant to improve output power, so the relaxors of Pb(Zn1/3NbM)O3, Pb(Mg1/3NbM)O3, Pb(Ni1/3NbM)O3, Pb(Ni1/2Wl/2)O3 et al with high dielectric constant should be added as the third component. Finally, for the manufacture demand of multilayer piezoelectric transformers (MPT), the low-melting additions, which had transient liquid-phase sintering mechanism, could be used to decreasing the sintering temperature andimproving the properties.Under the guide of the above rules, the systems of PZN-PZT and PMN-PZN-PZT were designed and the experimental plan was carried from two aspects of microstructure and macro-properties.By the two-step reaction, PZN-PZT ceramics with pure perovskite phase were prepared and the effects of Mn doping were studied in detail. The results were shown as follows: Mn dopant decreased the strength of Zn-O bond, which resulted in the increase of Zn-O bond length, so the pure perovskite phase of PZN was stabilized. Mn dopant also induced the lattice distortion of PZN-PZT system for Jahn-Teller effect. The system was transformed from the tetragonal to the rhombohedral with the addition of Mn. Curie temperature decreased with Mn addition, which resulted from the weak coupling of Mn-O bond. SEM photographs showed that the grain size increased gradually with Mn addition. When PZN-PZT system was sintered at 1050癈, the solubility of Mn was about 2wt% and beyond this limit, Mn would accumulate at the grain boundaries and decreased the density.On the respect of piezoelectric properties, Mn coexisted as Mn2+ and Mn3* in PZN-PZT system and suitable Mn doping as acceptor improv...
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