Study On The Preparation And Doping Y₂O₃ Of Low-voltage ZnO Varistor Ceramics

In this paper, low-voltage ZnO varistor ceramics were comprehensively analyzed. Properties, application,classification,method of low-voltage,studying situation and developing trend of low-voltage ZnO varistor ceramics were also discussed. The techniques and methods of low-voltage ZnO varistor ceramics were studied;The influence of forming pressure and agglomerant dosage in the forming process on properties of low-voltage ZnO varistor ceramics were researched too; The influence of sintering temperature,holding time and heating rate on the electrical properties and density of low-voltage ZnO varistor ceramics were also investigated. The sintering process of low-voltage ZnO varistors were optimized.The results show that forming limited pressure is 20Mpa and agglomerant dosages is 12wt%,the properties of low-voltage ZnO varistors is optimum; It can obtain the best conditions for sintering process when sintering temperature is 1200℃,holding time is 2 hours and heating rate is 7℃/min.Unlike conventional test method,this paper is first studied through the orthogonal test.According to the kinds of additives in low-voltage ZnO varistor ceramics,the effects of elements oxide Bi,Ti,Co,Mn,Sn,Sb on the characteristics of low-voltage ZnO varistor ceramics were studied respectively with the conventional processing of ZnO varistor ceramics. Finally, the optimum composition of low-voltage ZnO varistor is: 1.25%Bi₂O₃+0.4%TiO₂+ 0.4%Co₂O₃+1%MnO₂+1%SnO₂+1%Sb₂O₃+94.95%ZnO.The good characteristic with V1mA= 10.15V, IL= 2.05μA, =22.5 could be got at the proper sintering process.The influence of Y₂O₃ is used as additives on the electrical properties and mechanism of low-voltage ZnO varistor ceramics were studied.The results show that the addition of Y₂O₃ can increase the nonlinear coefficient of low-voltage ZnO varistors and decrease the leakage current,and at the same time improve the varistor voltage greatly.In addition,doping Y₂O₃ can reduce the size of ZnO grain evidently and make the grain size and distribution more uniform.