Percolation phenomena of field grading materials made of two kinds of filler

Electrical properties of the composites made with polybutadiene as a binder resin and SiC and/or Fe/sub 3/O/sub 4/ as filler have been studied. It has been found that the percolation threshold p/sub c/ of Fe/sub 3/O/sub 4/ of the composite made with SiC, Fe/sub 3/O/sub 4/ and resin increases with the volume fraction of SiC. It has been suggested that blobs, dead ends and loops on the percolating paths formed by SiC particles prevent the clusters of Fe/sub 3/O/sub 4/ from growing to be a percolating path. Thus, more loading of SiC leads to larger percolating threshold p/sub c/ of Fe/sub 3/O/sub 4/.