Dependence of the surface flashover properties of alumina on polishing abrasive parameters

Systematic investigations of the relationship between the surface finish, the polishing medium, and surface flashover properties of high purity polycrystalline alumina ceramics are reported. Samples polished with SiC abrasives displayed a linear behavior, with the breakdown strength increasing with decreasing surface roughness. The breakdown properties of the diamond polished samples were influenced significantly by the polishing sequence adopted; samples polished from coarser to finer finish exhibited erratic surface breakdown properties, whereas the breakdown properties of samples polished from finer to coarser finish varied linearly with respect to the particle size of the abrasive used in the final polishing. These results are discussed in terms of surface and subsurface defects that are formed during diamond polishing. The breakdown properties of the samples in relation to the abrasive type are also analyzed. >