Dielectric properties of porous materials

The authors consider materials were the major contribution to the electrical conductivity is given by the pore fluid, and in particular by ionic species dissolved in it. They propose qualitative models for two main kinds of dielectric response that have been observed in porous media. Their ideas are illustrated by experimental results on cement mortars and on glass beads and sand bonded by epoxy. The electrical properties of porous materials are of importance for a range of applications. For example, oil-impregnated paper is much used as an high voltage insulation material. The breakdown strength decreases and the dielectric losses increase as the water content in the pores increases