Influence of Grain Size, Oxygen Stoichiometry, and Synthesis Conditions on the γ-Fe2O3 Vacancies Ordering and Lattice Parameters

The soft chemistry method has been used to synthesize γ-Fe₂O₃ nanoparticles: various synthesis temperature were applied to obtain nanometric powders with crystallite size in the 9-14 nm range. Powders were characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectrophotometry, surface area measurements, and electron microscopy (TEM, SEM). It is clearly shown that these nanometric powders are very well crystallized as indicated by XRD and IR spectra which present substructural bands attributed to vacancies ordering (P4₁32). Based on these model materials and in the crystallite size range studied here, cell parameter appears to be not linked to crystallite size. It rather depends both on hydroxide adsorption and chemical composition.