Preparation And Properties Study Of ZnO Varistor Without Sb And Pb

Properties, application, type and study and development currents of zinc oxide varistor were discussed in this paper. The influence of structure, composition and properties of crystal and grain boundary in microstructure to ZnO varistor electrical were discussed too. Semi conducting properties of ZnO varistor, structure of its energy band and conductive mechanism of grain bounder energy band were analyzed. The effect of ZnO varistors ceramic powder pre-treatment on green density was studied. The results show that PVA did not make full effect before milling 30h and after milling 30h,the particles not only were favorable to being milled and prevented from aqqlomeration, but also the particles shape resulted to sphericity by adding to proper PVA(1%-3% powder weight) in the wet milling. At wet milling 40h and adding to PVA, the green density of varistors ceramic reached to 4.45g/cm³ by using drying press molding under uniaxial pressing at pressures of 180Mpa. The study of the true bismuth content in ZnO varistor show that detective limit was 1 ppm with the Inductively Coupled Plasma-Optical Emission Spectral analyzing bismuth content of sampling. Through optimizing sintering way, vaporization of bismuth was effective controlled. On the basis of last studied, the study of the effect of Nb₂O₅ replacing Sb₂O₃ doping on electrical properties of ZnO varistor founded that with the 0.105mol% amount of Nb₂O₅ doping the properties of ZnO ceramic were better in 1180℃ soaking temperature. Considering the higher soaking temperature, the effect of B₂O₃ doping and soaking of still existing liquid phase on microstructure and electrical properties were studied. The studied show that B₂O₃ doping had obvious effect in reduce soaking temperature, improved microstructure and optimizing electrical properties of ZnO varistor ceramic.