THE PERMEABILITY OF POLYCRYSTALLINE MATERIALS

This work addresses the relationship between grain properties, grain packing density, and the permeability and permittivity spectra of composite, polycrystalline material. The scattered multipolar fields about a single sphere are related to the polarizability of an ordered congregation of such spheres. Using the Clausius-Mossotti relation the effective permeability and permittivity spectra of a congregate polycrystalline material, formed by a cubic array of identical spheres, is determined for arbitrary packing density, permittivity, and permeability of the individual spheres. Although the spectra are considered over a range where the product of the external wave vector and sphere radius is kept small, typically less than one-tenth, the product of the internal wave vector and sphere radius is unrestricted. Changes in the packing density and internal wavelength have a dramatic effect on the calculated permeability and permittivity spectra.