Microstructure and current-voltage characteristics of multicomponent vanadium-doped zinc oxide varistors

The effects of the oxide additives MnO2, Co3O4, and Sb2O3, commonly incorpo rated in commercial Bi2O3-doped ZnO varistors, on the current-voltage chara cteristics and microstructure of 0.25 mol% V2O5-doped ZnO varistors have be en studied. MnO2 is the most significant additive in terms of its effects o n varistor performance. Varistor performance can also be improved by increa sing the V2O5 content to 0.5 mol% in a ZnO ceramic containing 1 mol% MnO2. Further increases in the V2O5 content of 1 mol% MnO2-doped material cause a deterioration in varistor behavior. The microstructure of the samples cons ists mainly of ZnO grains with zinc vanadates as the minority secondary pha ses. Additional spinel phase is formed when Sb2O3 is incorporated.