Properties Of Multi-component ZnO Varistor

ZnO Varistor belongs to the semiconductor resistor. Advantages of ZnO varistor are low cost, low residual voltage, small voltage coefficient, small leakage current, high nonlinear index and fast response time and so on. So it is widely used in power systems, electronic circuit, household appliances, especially in the fields of high performance surge absorber, over-voltage protection and zerotash arrester.Starting from the basic theory, the description of general properties and semiconductor properties of ZnO varistor in details are stated in this paper. The nonlinear characteristics of ZnO varistor is given. Finally, the conductive mechanism, microstructure and preparation technology of ZnO varistor are shown.In experiment part, ZnO varistor with different contents of Co₂O₃ doped were prepared by means of conventional technology. The electrical properties about varistor of Co₂O₃ doped to ZnO on the small current region is mainly studied, the relationship among doping concentration of Co₂O₃ and electrical properties and dielectric property is discussed. Then the microstructure of ZnO samples by X-ray diffraction is analyzed. And the effect of sintering temperature on the lattice structure of ZnO varistor samples is researched.The results show these: with the percentage of Co₂O₃ increasing, the varistor voltage promotes, the non-linear index becomes larger, leakage current reduces, dielectric loss reduces, and the current density of voltage falling positions reduces. With the increasing of applied voltage, the conductivity of sample increases, and the dielectric loss gradually becomes larger. The result of XRD shows these: With the sintering temperature rising, the half peak gradually narrowed, diffraction intensity increasing, while the crystallization quality of ZnO will be also improved. From all we have studyed above, the research of this paper have practical significance for the further application of ZnO varistors.