Investigation of the precursors of γ-Fe2O3 in Fe2O3/SiO2 nanocomposites obtained through sol–gel

Abstract The structure and the magnetic properties of a series of Fe2O3–SiO2 nanocomposites (16.9 and 28.5 wt% of Fe2O3/(Fe2O3+SiO2)), prepared by a sol–gel method and submitted to thermal treatments in a temperature range 300–700°C, were investigated through X-ray diffraction (XRD), transmission electron microscopy (TEM), Mossbauer spectroscopy and magnetometry. Poorly crystallized particles, belonging to the 2-line ferrihydrite phase, were found in all the samples and recognized as precursors of the γ-Fe2O3 that form in Fe2O3–SiO2 nanocomposites at T>700°C. The result was achieved through a detailed comparison of structural and magnetic properties of nanocomposites with a bulk iron (III) oxide hydrated reference sample.