SYNTHESIS AND CHARACTERIZATION OF SOME IRON-OXIDES BY SOL-GEL METHOD

Several iron oxides and mixtures of iron oxides have been prepared by heating the product of a sol-gel reaction between iron(III) nitrate and ethylene glycol in different atmospheres and at different temperatures. The materials were characterized by Mossbauer spectroscopy, powder X-ray diffraction, and transmission electron microscopy. Ferrous iron was found to be present in an appreciable amount in the products of the sol-gel reaction, but its origin is not yet understood. Heating at 300-degrees-C in N2 atmosphere, cooling in air to ambient temperature, and heating again at 300-degrees-C in static air produced single-phase maghemite with a mean crystallite diameter (MCD) of 18 nm. Well crystallized hematite (MCD = 110 nm) was obtained at 300-degrees-C in O2 atmosphere. Mixtures of poorly crystallized maghemite and magnetite were observed to exhibit room-temperature Mossbauer spectra which closely resemble those reported for sodium-modified maghemite. A mixture of magnetite, wustite, and metallic iron was obtained by heating at 800-degrees-C in N2 atmosphere. (C) 1994 Academic Press, Inc.