Dielectric properties of smectite clays

The dielectric properties of a series of smectite clays, namely, Na+, Li+ and Cu++-fluorohectorites, Na+ montmorillonite and Na+ laponite have been measured as a function of water content over the frequency range 40-10(5) Hz. These clays span a wide range of particle sizes, surface areas, charge densities and intercalant exchange cations. The objective of this study was to correlate the dielectric properties with these variables. In general the dielectric constant changes slowly as the first monolayer of absorbed water builds up in the galleries. Water loadings beyond the first monolayer cause the dielectric constant to rapidly rise to very high values. The relative permittivity and the conductivity increase with increasing layer charge density and with decreasing charge to radius ratio of the gallery cation. This suggests that the cations rather than the protons are the main current carriers. The frequency dependence is measured and discussed.