Large influence of the synthesis conditions on the physico-chemical properties of nanostructured Fe3O4

Magnetite synthesized via three different synthesis routes (coprecipitation process in aqueous media, electrochemical synthesis in presence of complexing agents and solid state reaction at high temperature) has been characterized by X-Ray diffraction, scanning electron microscopy, thermal analysis (TGA), FT-IR and Mössbauer spectroscopies. Although each procedure gave homogeneous magnetite powders, many differences could be seen in the physico-chemical properties of the samples mostly depending on the synthesis conditions. For instance, at least two factors seem to have a huge impact onto the Fe₃O₄ behaviour: the presence of hydration water molecules and the particle size of the powders since a superparamagnetic behaviour was observed with the thinnest particles, at room temperature, on the Mössbauer spectra via the appearance of line broadening and a pronounced central doublet.