Sol-gel derived iron oxide-silica nanocomposites, starting from iron chloride and iron nitrate

Sol-gel FezO(3)-SiOz composites have been obtained, using tetraethoxysilane as precursor and ferric salts (chloride and nitrate), for a target composition of 32 wt. % Fe2O3. The samples were characterized by thermal analysis, transmission electron microscopy, electron diffraction and X-ray diffraction. Mossbauer spectroscopy showed that some of the resulting materials possess superparamagnetic and ferrimagnetic properties, indicating a distribution of particles size in nanometer and tens of nanometers range, The different results obtained suggest that the formation of iron oxide phases depends on the precursors employed and the atmosphere of thermal treatment.