Electromigration interstitial diffusion

An applied electrical potential gradient can induce diffusion (electromigration) in metals due to a cross effect between the diffusing species and the flux of conduction electrons that will be present. When an electric field is applied to a dilute solution of interstitial atoms in a metal, there are two fluxes in the system a flux of conduction electrons, Jq, and a flux of the interstitials, J. For a system maintained at constant temperature with Fq = -V = E, Eq. 2.21 gives... 

A variety of solutes in the rare earth metals present a partly or total interstitial character. These solutes include beside the metalloid classical interstitials also some metallic elements, the so-called fast-diffusers, discussed in section 4. In general the study of electromigration of interstitials offers two advantages as compared to that of substitutional solutes. From the experimental point of view, the relatively high mobilities of the interstitial solutes increases the electrotransport effects often allowing to achieve steady state conditions within... 

---