Critical behavior of the electrical transport properties in a tunneling-percolation system

Abstract

We report the confirmation of the tunneling-percolation model predictions by measurements on carbon black-polymer composites, in which the carbon black is of ``low structure.'' From the measurements we have determined the critical resistance exponent t, and the ratio $\ensuremath{\kappa}/t,$ where \ensuremath{\kappa} is the critical relative resistance-noise exponent. The results found are $t=6.4$ and $\ensuremath{\kappa}/t=0.5.$ It is shown that these simultaneous new t and $\ensuremath{\kappa}/t$ results are consistent only with the predictions of a tunneling-percolation model. It is argued that previously reported values of t and $\ensuremath{\kappa}/t$ in similar systems, which deviate from the theoretical predictions of this model, are due to nonrandom dispersion of the particles in these systems.