PERCOLATION APPROACH TO THE BARRIER-CONTROLLED CONDUCTIVITY OF CERAMIC COMPOSITES

The temperature and composition dependence of the barrier-controlled c onductivity of two-phase composites is analysed reducing the problem t o that of the site-bond percolation. It is shown that the critical bar rier height depends on the volume fraction phi of the conducting phase , this giving rise to a specific phi-dependence of the activation ener gy of the conductivity near the percolation threshold. Approximate rel ations suggested for the phase boundary function of the site-bond prob lem make it possible to evaluate the distribution of inter-grain barri er characteristics from the measurements of the temperature and compos ition dependence of the conductivity near the percolation threshold.