Effect of particle size ratio on the conducting percolation threshold of granular conductive-insulating composites

In this paper, we apply Monte Carlo simulation to investigate the conductive percolation threshold of granular composite of conductive and insulating powders with amorphous structure. We focus on the effect of insulating to conductive particle size ratio lambda = d(i)/d(c) on the conducting percolation threshold p(c) (the volume fraction of the conductive powder). Simulation results show that, for lambda = 1, the percolation threshold p(c) lies between simple cubic and body centred cubic site percolation thresholds, and that as lambda increases the percolation threshold decreases. We also use the structural information obtained by the simulation to study the nonlinear current-voltage characteristics of composite with solid volume fraction of conductive powder below p(c) in terms of electron tunnelling for nanoscale powders, dielectric breakdown for microscale or larger powders, and pressing induced conduction for non-rigid insulating powders.