Diffusion in Ionic Solids

In charged particles systems or ionic solids, diffusion is always accompanied by charge transfer, thus leading to electrochemical phenomena depending on the nature of electrodes. We will learn how to describe mass/charge transport phenomena in terms of mobile charged components with actual charges and in terms of mobile structure elements with effective charges and the resulting electrical properties, ionic and electronic conductivities. There arises flux coupling to keep the local charge neutrality, which results in another type of chemical diffusivity called the Nernst-Planck type, in comparison with the Darken-type earlier in Chap. 4. The self-diffusivities are discussed on the basis of the equilibrium defect structure of a given system as well as the chemical or ambipolar diffusion in concentration gradients and nonstoichiometry re-equilibration kinetics in terms of the Nernst-Planck-type chemical diffusivity.