Dielectric dispersion of salt-water-saturated porous glass containing thin glass plates

Complex permittivity (i.e., dielectric constant and conductivity) measurements are performed on porous, fused glass bead specimens, and the effect of the presence of glass plates is investigated systematically. Two types of plates are used in this investigation, relatively thick ones made from crushed cover slides and very thin ones made from crushed blown glass bubbles. As a reference, the response of specimens without plates is also measured. After saturating the specimens with conducting water, the effective dielectric function is measured over the frequency range of Maxwell-Wagner dispersion. The dispersion strength increased with the addition of plates, an effect that is stronger for thinner plates. The dispersion frequency range is larger for thinner plates, but is independent of plate concentration for constant plate thickness. The experimental results are compared with the effective medium theory for the dielectric function of porous media containing plates due to Mendelson and Cohen and to Sen-an extension of the Sen Scala Cohen theory. The theoretical curves are fitted to the experimental points of the real dielectric constant by adjusting the depolarization parameter given by the aspect ratio of the plates. The effect of the plates on the dispersion predicted by the theory is found to be in,good agreement with experimental result. The high-frequency level of the real dielectric constant is almost unaffected by the plates as given by the theory. The low-frequency level of the conductivity, or the formation factor, is found to vary with plate content, as also predicted by the theory. However, the quantitative difference between the theoretical and the experimental formation factor is generally found to be somewhat larger than the estimated experimental uncertainty. The theory is also fitted to data from the literature on a real rock specimen, and a close fit is obtained, together with encouraging estimates of porosity and formation factor.