Study On Electrical Properties And Temperature Stabilities Of PNW-PMN-PZT Quaternary Piezoelectric Ceramics

In recent years, with the development of the electric apparatus of PZT,piezoelectric ceramics have been extensively used. The high power piezoelectricmaterials have become more important developmental aspect in the practical application.In order to improve the electricial properties and the temperature stabilities of the0.03PNW-0.07PMN-0.90PZT system and statisfy the requirement of the high powerpiezoelectric material practical applications, the doping and the variation of Zr/Ti ratioson the 0.03PNW-0.07PMN-0.90PZT were investigated in this work.Firstly, PNW-PMN-PZT+0.1wt.%CeO₂ ternary system piezoelectric ceramics ofthe different additions of WO₃ and Pb₃O₄ were successfully prepared by theconventional mixed-oxide method. The results revealed that the major phase structureof all samples was pure perovskite phase. With the WO₃ content increasing, K_p, Q_mand d₃₃ showed the same tendency that was increase rapidly at first and got itsoptimisted value at the addition of 0.6 wt. % WO₃, then decrease with further increasingWO₃ content. As appropriate Pb₃O₄ was added to the system, both density andelectrical properties of ceramics were enhanced. It was believed that PbO-WO₃additive could result in liquid-phase formation during the sintering process withincreasing Pb₃O₄ content, which densified the ceramics. When sintering temperaturewas 1150℃, the highest density was achieved and the values were 7.70 g/cm³ at the 0.5wt.% Pb₃O₄ excess. Moreover, the optimized electrical properties were also obtained,which were K_p=0.66, Q_m=1318, d₃₃=430 pC/N,ε_r=2229 and tanδ=0.0066,respectively. Meanwhile, the temperature stabilities wereâ–³f_r/f_r25℃=-0.671% andâ–³K_p/K_p25℃=2.065%, which need to been improved. Therefore, 0.9Pb (Zr_0.52Ti_0.48) O₃-0.03Pb (Ni_1/2W_1/2)O₃-0.07 Pb (Mn_1/3Nb_2/3)O₃+0.1wt.%CeO₂+0.6 wt.% WO₃+0.5wt.%Pb₃O₄ (PNW-PMN-PZT) was selected as the basic system in our study.Secondly, there are some reports which show materials composition far from theMPB in the tetragonal region has negative TCF. Moving toward the MPB from T to Rregions changes the TCF from negative to positive. There exists a composition (M)where the TCF is zero and the better electricial properties were achieved. In order tofind the composition of M, Effect on Zr/Ti ratos on the electricial properties andtemperature stabilities of 0.03PNW-0.07PMN-0.90PZT+0.1wt.% CeO₂+0.6%WO₃+0.5 wt.%Pb₃O₄ were investigated. The optimized and better emperaturet stabilities wereobtained at Zr/Ti=50/50, which were K_p=0.55, Q_m=1707, d₃₃=342 pC/N,ε_r=1923, tanδ=0.0055,â–³f_r/f_r25℃=-0.304% andâ–³K_p/K_p25℃=-1.801%, respectively.Lastly, in order to further improving the temperature stabilities and the electricalproperties for the demands of the high power piezoelectric ceramic practical application,CeO₂ and Cr₂O₃ were added to the system. The results revealed the composition with0.1wt. % CeO₂ and 0.2 wt.% Cr₂O₃ had the optimited temperature stabilities and theoptimited electrical properties, which were K_p=0.54, Q_m=1730, d₃₃=330 pC/N,ε_r=2078, tanδ=0.0052,â–³f_r/f_r25℃=-0.167% andâ–³K_p/K_p25℃=-1.391%.0.9Pb(Zr_0.50Ti_0.50)O₃-0.07Pb(Mn_1/3Nb_2/3)O₃-0.03Pb(Ni_1/2W_1/2)O₃+0.1wt.%CeO₂+0.5wt.% Pb₃O₄+0.6wt.%WO₃+0.2 wt.%Cr₂O₃ were selected as superior composition basedon the former researches, which makes the ceramics with this composition to be satisfyfor high power piezoelectric ceramic practical applications.