Dispersion and Absorption in Dielectrics II. Direct Current Characteristics

In the first paper of this series [J. Chem. Phys. 9, 341 (1941)], it was shown that the complex dielectric constant, ε*, of many liquid and solid dielectrics is given by a single very general formula ε*=ε∞+(ε0−ε∞)/[1+(iωτ0)1−α].In this equation ε0 and ε∞ are the ``static'' and ``infinite frequency'' dielectric constants, ω = 2π times the frequency, τ0 is a generalized relaxation time and α is a constant, 0 < α < 1. The transient current as a function of the time, t, after application of a unit constant potential difference has been calculated from this expression in series form. For times much less than τ0, the time dependence is of the form (t/τ0)−α, and for times much greater than τ0, it is of the form (t/τ0)−(2—α). The transition between these extremes occurs for the range in which t is comparable with τ0. The total absorption charge, which is the integral of the exact expression, is always finite. Although many transient data for dielectrics are of the predicted form, none have been taken over a sufficiently wide range of times adequately to test the result, nor is it yet possible to determine either the relaxation time or the static dielectric constant from available data.