Chemical Diffusion Through Grain Boundaries in Mixed Conductors

Chemical diffusion through boundaries involving two charged diffusing species (e.g., and 2e − in an oxide) is modeled taking into account Poisson's equation, restricted to dilute systems and small driving forces. The results are compared with conventional treatments on a single crystal. Grain boundary effects are exemplified for ( i ) a bicrystal containing a grain boundary with adjacent space‐charge layers and ( ii ) a polycrystal involving space‐charge‐free amorphous grain boundaries. Numerical results ( i ) are analyzed in the context of recent experiments on a bicrystal. Transmission‐line approximations for chemical diffusion in polycrystals are proposed and briefly compared with exact results.