A phenomenological theory was presented for the time-dependence of the relaxation process of an α-phase sample which had been previously polarized by the application of a voltage. The electromotive force caused by the internal electric field due to the polarized charge distribution was given, by a series of exponential terms, as a function of Dt. The diffusion constants were obtained at several temperatures. In addition, the alternating-current conductivity was measured for the same specimen. The results were analyzed with the aid of a generalized Drude theory. By using the results for the diffusion constant and the alternating-current conductivity, deviations from the Nernst-Einstein relationship were derived. Computer simulations of these quantities were carried out by using well-established pair-wise potentials, and the agreement was found to be satisfactory.

T.Koishi, M.Kusakabe, S.Tamaki: Ionics, 1999, 5[1-2], 100-5