AC and DC conductivity based microstructural characterization of composites

The microstructures, upon which the widely used Maxwell Wagner (MW) and the Bruggeman Symmetric (BS) and Anti-symmetric (BA) Effective Media (EM) theories are based, are presented and the limitations of these methods discussed. This approach is illustrated using some recent results on 8 mole% Yttria Stabilized Zirconia, The microstructures characterizing percolation systems and the resultant critical volume fractions arc presented. A new two exponent phenomenological model, which enables percolation concepts to be used for realistic binary composites, is introduced. DC and AC conductivity results for a series Graphite- Boron Nitride composites and TiC - Al2O3 ceramic arc given to illustrate relevant experimental percolation results.