Chemical diffusion with non-constant Dδ and the appearance of a parabolic rate law: Model study on SrTiO3†
Abstract
The chemical diffusion of oxygen in Fe-doped SrTiO3 single crystals driven by large changes in the ambient oxygen partial pressure pO2 is studied. The stoichiometry dependence of the chemical diffusion coefficient Dδ is derived from the concept of conservative ensembles for two independent trapping reactions. Finite difference simulations show that the stoichiometry dependence of Dδ can lead to the appearance of a parabolic rate law (which typically applies to two- or multiple-phase systems) even in single-phase systems, provided a strong increase of Dδ occurs in the outer sample region.