Permittivity and density relationships for granular and powdered materials

When the permittivities, or dielectric properties, of granular or powdered solid materials are important, some reliable relationship between the permittivity and the bulk density of the air-particle mixture is required. Dielectric mixture equations have been developed and investigated for this purpose. An extrapolation procedure, based on the linearity with density of functions of the real and imaginary parts of the permittivity of pulverized and granular materials, has also been used to obtain estimates of the permittivity of the solid material. Both of these methods, calculation by dielectric mixture equations and the extrapolation procedure, are described in this paper for estimating the permittivity of solids from measured permittivity data on granular or powdered samples of those materials.