Effect Of Rare-earths Oxide On The Performance Of Zinc Oxide Varistor And Study On The Microstructure Of Zinc Oxide Varistor Containing Rare-earths Oxide

The influences and mechanisms of rare-earths oxide additives La2O3 on the electrical performance of zinc oxide varistor were explored in this paper.Microadded rare-earths oxide in traditional raw materials of zinc oxide varistor, researched the influences of rare-earths oxide on the electrical performance of zinc oxide varistor , and selected the optium composition of various rare-earths oxide additives. The results of experiment indicated that adding a appropriate amount of rare-earths oxide in zinc oxide varistor led to increase potential gradient greatly, decrease leakage current with voltage ratio no changed. When the Nd2O3 content is 0.04mol%, potential gradient of zinc oxide varistor is maximum, improves about 65% compared with zinc oxide varistor no containing Nd2O3, voltage ratio and leakage current are the lowest. So the optium content of Nd203 is 0.04mol% in this study. When the CeO2 content is 0.06mol%, potential gradient is maximum, improves about 30%, voltage ratio is lower, and leakage current is the lowest. So the optium content of CeO2 is 0.06mol% in this study. When the La2O3 content is 0.04mol%, potential gradient is the highest, and improves about 57%, voltage ratio is lower, leakage current is minmum. So the optium content of La2O3 is 0.04mol% in this study. Synthetic analyze that effect of Nd2O3 on improving potential gradient is the most outstanding, effect of La2O3 is more outstanding and that of CeO2 is theinferior. Adding appropriate amout Nd2O3 improves remarkably potential gradient, at the same time decrease leakage current and voltage ratio, that results in zinc oxide varistor with excellent comprehensively performance.Microstruture of zinc oxide varistor was researed with the help of scanning electronic microscope(SEM), energy spectrum apparatus(EPD), X-ray diffraction(XRD), and microscopic image analyzing system. It is suggested that microadding rare-earths oxide Nd2O3,CeO2,La2O3 can reduce the grain size because the phases containing rare-earths element-both CeO2, La2O3, which are independent phases, and the new phase Na2Nd2Sb2(Zn2AlO12) containing neodymium all lie in the grain boundary, form the intergranular resistance layers with Zn2.33Sb0.67O4, hinder the movement of grain boundary, make growth rate of zinc oxide varistor grain slow during sintering, which reduce the grain size and make the grain well-distributed. Moreover, CeO2 and La2O3 can change the concentration of interstitial zinc [zni], and finally control growth rate of zinc oxide varistor grain, improve potential gradient through changing the concentration of free electrons of zinc oxide grain during sintering. Microadding a appropriate amount of rare-earths oxide can decrease leakage current by means of raising the height of barrier potential and increasing grain resistivity of zinc oxide.In short, adding appropriate amount rare-earths oxide can improve potential gradient greatly, decrease leakage current with voltage ratio no changed and make zinc oxide varistor with outstanding comprehensively performance.