Dynamic segregation during ferrite oxidation revealed by XPS

Dynamic segregation phenomena were revealed by XPS during the oxidation of some ferrites (Fe 2.5 Ti 0.5 O 4 , Fe 2.5 Ni 0.5 O 4 , Fe 2 CrO 4 and FeCr 2 O 4 ). This kind of phenomenon induces, at a low temperature (below room temperature), drastic changes in the cationic composition of the most external layers. Dynamic segregation is a function of the cationic composition, the oxidation capability and the morphology of these ferrites. Although dynamic segregation seems to be a quite frequent phenomenon that often can be observed during ferrite oxidation, there are materials in existence where it does not appear, such as molybdenum ferrite.