The high-frequency dielectric dispersion of a colloid

Abstract

The dielectric response of a colloid in which the particle radius a is much greater than the double-layer thickness κ-1 is investigated. Such colloids exhibit two types of dielectric dispersion: one at frequencies of order D/a2, and the other at higher frequencies of order κ2D where D is the ion diffusivity. It is the high-frequency dispersion that is of interest here. The calculation of this dispersion is greatly simplified by the fact that the applied field has a negligible effect on the ion densities in the electrolyte. Thus there is no diffusive component to the electric current, and the double layer and surrounding electrolyte can be treated as simple conductors. By combining the solution for the electrical potential around an isolated sphere with the corresponding result obtained by S. S. Dukhin and V. N. Sbilov ("Dielectric Phenomena and the Double Layer in Disperse Systems and Polyelectrolytes." Wiley, New York, 1974) for the low-frequency regime we construct a complete picture of the dielectric response of a dilute suspension of spheres. To illustrate the effect of particle concentration on the form of the dielectric dispersion, computed values are presented for a random close-packed array of spheres. © 1986.