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

We report the confirmation of the tunneling-percolation model predictions b y measurements on carbon black-polymer composites, in which the carbon blac k is of "low structure." From the measurements we have determined the criti cal resistance exponent t, and the ratio kappa/t, where kappa is the critic al relative resistance-noise exponent. The results found are t = 6.4 and ka ppa/t = 0.5. It is shown that these simultaneous new t and kappa/t results are consistent only with the predictions of a tunneling-percolation model. It is argued that previously reported values of t and kappa/t in similar sy stems, which deviate from the theoretical predictions of this model, are du e to nonrandom dispersion of the particles in these systems. [S0163-1829(99 )02316-4].