Improved Performance Of ZnO Varistors

Liquid preparation of the composite ultra-fine powder additive is used to prepare those ZnO varistors which have stabler internal structure,lower porosity rate, and narrower range particle size distribution. These additives elements also present more uniform distribution. It makes the ZnO varistors present better performance. The chemical coprecipitation and the sol-gel method which prepare composite ultra-fine powder are introduced,and the ZnO varistors with its particle size below 10μm are prepared.Three most important elements,Mn, Co and Bi, will be a total of the precipitation in the chemical coprecipitation,and then the composite ultra-fine powder is prepared. ZnO varistors what are made of the composite ultra-fine powder, ZnO powder and the other additive powder are made into cylinders with diameters of 8.5mm and height of 1mm.The performance of these ZnO varistors is better than that of the ZnO varistors made by the solid phase method. The 8/20μs surge absorption capability of ZnO varistors made by chemical coprecipitation can be achieved 2100A, and the 2ms rectangular current pulse capability can be achieved 70J, when they can be achieved 1900A and 35J made by solid phase method.,Mixed liquid including five elements,Mn,Co,Bi,Cr and Zr,was made into colloid in the sol-gel method experiment. The composite ultra-fine powder additive were prepared after the calcination. The performance of ZnO varistors made by sol-gel method was a little better than solid phase method. Because of its imperfect process, the performance of ZnO varistors made by sol-gel method was worse than the chemical coprecipitation,which had perfect process.Those elements were tested by X-ray fluorescence spectrometer of those elements made in three various methods,so that their content in those elements was identical.Then advantages and disadvantages of these three methods appeared,and then the formulation were improved. Heat treatment and electrical ageing proceed were researched to improve performance of elements,and the suitable heat treatment and electrical ageing proceed can obviously improve performance of elements...