Abstract
It has been expected that the ac conductivity σ AC of conductive particle-polymer composites varies as a power of frequency f, such as σ AC ∝ fq with q=0.8-0.9 above the percolation threshold pc. In this paper, how finite carbon black (CB) clusters contribute to the ac electrical conduction in CB-polyethylene composites below and above pc is discussed. It was found that the frequency dependence of σ Ac below pc is directly proportional to f, being due to ac loss current, and a tunneling current taking place between the finite CB clusters appears in addition to the ac loss current for the volume fraction of CB very close to pc. Above pc, the ac loss current still appears, indicating that a hopping conduction between finite CB clusters does not take place and conducting pathways between electrodes govern the ohmic electrical conduction at least till 1 MHz.
