Percolation phenomena and electrical conduction mechanism of carbon black-polyethylene composites

In this paper, how finite or infinite carbon black (CB) clusters contribute to the ac conductivity σ_AC in CB-polyethylene composites below and above the percolation threshold p _c is discussed. It was found that the frequency dependence of σ_AC below p_c is due to ac loss current and a tunneling current between the finite carbon black clusters appears in addition to the ac loss current for the volume fraction of CB, p, very closely to p_c. Above p_c, a current independent of frequency governs σ_AC although the ac loss current still appears, which leads to a conclusion that a hopping conduction via finite clusters does not take place at least till 1 MHz