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 are 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 — Al[sub 2]O[sub 3] ceramic are given to illustrate relevant experimental percolation results. [ABSTRACT FROM AUTHOR]