Research On Lead Nickel Niobate-Lead Zirconate Titanat Ternary Piezoelectric Ceramics

Two kinds of lead nickel niobate-lead zirconate titanat ternary piezoelectricceramics was studied. We distinguished them from the ratios of Ni and Nb. One of thesolid solution was 0.3Pb(Ni_1/3Nb_2/3)O₃-0.7Pb(Zr,Ti)O₃ (abbreviations for0.3PNN-0.7PZT), the Ni/Nb of which was 1:2. When Ni/Nb was 1:1, we called thesolid solution for 0.3Pb(Ni_1/2Nb_1/2)O₃-0.7Pb(Zr,Ti)O₃ (abbreviations for0.3PNN(1:1)-0.7PZT).In this paper, we studied the influence of different synthesised methods,calcination temperature, sintering temperature and Zr/Ti on the phase structure andperformance of 0.3PNN-0.7PZT piezoelectric ceramics. The X-ray diffraction(abbreviations for XRD) indicated that piezoelectric ceramics with single perovskitestructure could be successfully synthesised by the traditional oxide method. Zr/Tiwould influence the position of morphotropic phase boundary (abbreviations forMPB). When calcinated at 900℃, sintered at 1200℃, the crystal transformsed fromtetragonal to rhombohedral gradually with the increasing of Zr/Ti and the MPB locatedat Zr/Ti=44/56, where we could get the excellent properties.Moreover, the effect of poling condition on the dielectric and piezoelectricproperties of 0.3PNN-0.7PZT ceramics had been studied. When poled at 2 kV/mm for10min in a silicon oil bath at 60℃, the ceramics obtained the optimal properties: therelative permittivity ( 33 0εTε), dielectric loss (tanδ), piezoelectric constant (d33),electromechanical coupling factor (Kp) were 2451, 1.7%, 538 pC/N and 0.637,respectively.In addition, the doping modification of La₂O₃ on 0.3PNN-0.7PZT piezoelectricceramics was studied. The XRD of La₂O₃ doped 0.3PNN-0.7PZT ceramics indicatedthat the system formed well crystallized perovskite structures with different content ofLa₂O₃ dopant. Similarly, the Zr/Ti had also played an important role in the La₂O₃doped 0.3PNN-0.7PZT ceramics. When the sintering temperature was 1270℃, theLa₂O₃ dopant was 2 mol% and the ratio of Zr/Ti was 44/56, the ceramics located atMPB and showed excellent properties.On the other hand, we studied the low temperature sintering CuO doped0.3PNN-0.7PZT ceramics. The results showed that the reaction between CuO andPbO yielded the liquid phase, which made the sintering temperature drop from 1200℃to 900℃, however, the properties were bad. When sintered at 1050℃, dopedwith 1 mol% CuO, the ceramics showed better comprehensive performances.The effect of sintering temperature and Zr/Ti on the phase structure andproperties of 0.3PNN(1:1)-0.7PZT was discussed. From the results of XRD, not onlythe perovskite solid solution structure, other phases: NiO, ZrO₂ and PbO also could bedetected, which made the piezoelectric properties worse. Compared with0.3PNN-0.7PZT, this system exhibited the phenomenons: the decrasing of dielectricloss and piezoelectric performance together with the improvement of Tc, whichdemonstrated the characteristics of hard dopant. When sintered at 1220℃, Zr/Ti was46/54, good performance could be found.