DISPERSION OF FE2O3 SUPPORTED ON METAL-OXIDES STUDIED BY MOSSBAUER-SPECTROSCOPY AND XRD

The dispersion of Fe2O3 on various metal oxide supports (SiO2, gamma-A l2O3, CeO2, ZrO2 and TiO2) has been studied by Mossbauer spectroscopy and XRD. The vacant sites on the surface of the support significantly influence the form of the iron oxide. For silica-supported iron oxide, Fe3+ cations concentrate readily to form crystalline alpha-Fe2O3 part icles, owing to the lack of vacant surface sites on silica. However, f or other metal oxide supports, such as gamma-Al2O3, CeO2, ZrO2 and TiO 2, which have vacant surface sites, Fe3+ cations are preferentially in corporated into the vacant surface sites and the chemical surroundings of these Fe3+ cations, incorporated in different types of surface sit es, are different. Crystalline alpha-Fe2O3 particles appear after all usable vacant sites have been occupied by Fe3+ cations.