The electrochemical excitation method and its applications to silver sulfide-based materials.

摘要

The purpose of this research was to develop a novel electrochemical excitation method to study atomic diffusion in the mixed ionic-electronic conducting solids, and to apply it to silver sulfide-based materials. In the method, an oscillating voltage was applied to a rod-shaped sample at one end through an electrochemical cell. This excited a chemical potential oscillation of a diffusant, which propagated into the sample as a wave. An amplitude attenuation and a phase shift of the wave were determined from two emf-time curves collected on two electrochemical cells positioned along the sample rod. Diffusional properties of the sample materials were evaluated by fitting the wave parameters in space or frequency, with mathematical relations derived from solving Fick's second law with the Laplace transformation under the appropriate conditions.;The excitation method has been applied to (i) a homogeneous sample of Ag;For the bisectional sample, the chemical diffusion coefficients of Ag;The significance of this study lies in that (i) chemical diffusion coefficients can now be measured with a much higher precision; (ii) other materials properties such as thermodynamic parameters, can be evaluated with the frequency approach; and (iii) the high precision coupled with the ability to measure diffusion coefficients at different frequencies makes it possible to separate individual mechanisms of diffusion into different frequency regions.