| Abstract Scope |
In contrast with the bulk phase, an extended defect (dislocation, grain boundary, surface, domain wall) in an ionic solid is not constrained in equilibrium to remain locally electroneutral. Because of interactions between the extended defect and point defects, the extended defect will in general become electrostatically charged, with the adjacent bulk phase concomitantly developing diffuse, enveloping space-charge zones.The altered concentrations of point defects in these space-charge zones have long been understood to affect, for instance, the transport of charge across grain boundaries in polycrystalline systems. In this presentation, I will draw attention to two aspects that have received far less attention: that space-charge zones can affect the excess Gibbs free energy of a grain boundary; and that space-charge zones can provide an unusual contribution to accelerated diffusion along grain boundaries. Throughout the presentation, I will emphasise the need to consider space-charge zones from a thermodynamic perspective. |