Defect chemistry and chemical transport involving interfaces

The impact of boundaries on electrical conductivity and chemical diffusion is discussed. The equilibrium point defect chemistry of boundaries is described by the core-space charge model. Conductivity effects are briefly touched upon. The chemical transport is discussed in more detail using a linearised Nernst-Planck-Poisson set of equations. In the steady state the model is applied to three simple situations: (i) enhanced diffusion along, (ii) hindered diffusion across laterally homogeneous boundaries and (iii) diffusion through poorly connected grains. In the transient regime the impact of blocking grain boundaries is considered. (C) 1999 Elsevier Science B.V. All rights reserved.