Diffusion-induced grain-boundary migration was observed during the internal reduction of Cr-doped material. The chemical diffusion of O along grain boundaries was fast when compared with volume diffusion, and the internal reduction front therefore penetrated from the grain boundaries and into the grains; leading to Cr precipitation and the formation of a thin coherently-strained Cr-depleted oxide layer. Migration of the grain boundary to either side occurred, while the global energy in the swept area decreased; due to O potential relaxation, precipitate coarsening and elastic strain relaxation.

M.Backhaus-Ricoult, A.Peyrot-Chabrol: Philosophical Magazine A, 1996, 73[4], 973-98