Non-conducting inclusions in a conducting matrix: Influence of inclusion size on electrical conductivity

The influence of reinforcement size on the electrical conductivity of a metal matrix composite with discrete electrically insulating reinforcements is analyzed and the resulting theoretical expression is confronted with experiment. An experimental technique is presented to separate the influence of the tortuosity of the conduction path from size effects. It is shown that the observed size effect can be rationalized by additional scattering of the conduction electrons on the metal-ceramic interface and that scattering at geometrically necessary dislocations due to cool-down of the composite from processing temperature is much less important.