J. Phys. IV France 07 (1997) C1-249-C1-252
Mixed-Valence Defect Ferrites : a New Family of Fine Powders and Thin Films of Spinel FerritesP. Tailhades1, B. Gillot2 and A. Rousset1
1 Laboratoire de Chimie des Matériaux Inorganiques, Université Paul Sabatier, ESR-CNRS 5070, 118 route de Narbonne, 31062 Toulouse cedex, France
2 Laboratoire de Recherches sur la Réactivité des Solides, Université de Bourgogne, URA 23 du CNRS, BP. 138, 21004 Dijon, France
When highly divided spinel ferrites become reactive enough with oxygen, to allow the oxidation of the Fe2+ ions at low temperature and of substitute cations too, when these cations are capable of different valence states. We prepared fine particles of spinel ferrites substituted by Mn, Mo, Cu, by "chimie douce", especially from oxalate precursors and used them to reveal and to study the oxido-reduction phenomena occurring in these finely divided materials. It was shown that the oxidation created a new family of spinel ferrites : the mixed-valence defect ferrites, having specific characteristics and properties. The ferrites of this type can be fine powders prepared at low temperature, or ground ferrites obtained at high temperature, or thin films.
© EDP Sciences 1997