Iron(II) cobalt ferrites. Preparation and interfacial behaviour

Abstract

Relations between the interfacial and the chemical-structural features of oxides are of concern in several fields. Ferrites appear as a particularly suitable system as they allow gradual changes in composition while avoiding complications from structural modifications. A family of iron(II) cobalt ferrites (Co_xFe_3–xO₄, 0.25 < x < 1) was prepared by a wet procedure and characterized for phase purity and cationic Co/Fe composition. Auger surface analyses showed that the Co/Fe ratio does not undergo significant modifications in passing from the bulk to the surface. Parameters of the electrical double layer (pH_p.z.e. and isoelectric point) have been determined for all the oxide compositions. Results show that the pH_p.z.e. and isoelectric point values vary as a continuous function of the degree of substitution of Co for Fe.