An X-Ray Study of the Wüstite (FeO) Solid Solutions

A series of iron oxides with compositions between 76.08 and 76.72 percent Fe, all of them lying within the single phase solid solution area known as Wüstite has been prepared and the lattice constants and densities of the individual members determined. The NaCl structure found by earlier investigators and considered by them to be the structure of FeO has been found throughout this series. Contrary to the earlier results the size of the unit cell decreases as the iron content decreases. The solid solution is of a complex type; an oxygen ion replaces an FeO group with an accompanying increase in valence of 2 Fe++ to 2 Fe+++. The results are discussed from the chemical and structural points of view.