A few aspects about the manufacturing process of five and two additives metal oxides varistors [articol]

Abstract

ZnO based varistors are today used for making state of the art surge arresters for all voltage levels. Essentially they are “n” semi-conductor ceramics made of ZnO (more than 90% molar percents) and many other oxides having different structural roles. This paper presents a new manufacturing technology based on 2 additional oxides Cr₂O₃ and MnO₂, compared with the old one, having five oxides (Cr₂O₃, MnO₂, Co₃O₄, Bi₂O₃, NiO). This varistor material has a smaller electrical capacity, suitable for telecommunication applications. The chemical compositions of this new material as well as all the phases of the manufacturing process are presented too [1]. Table 1 shows the initial chemical composition of the varistor. The last four additives will be lost by evaporation after finishing the manufacturing process [2].