Correlation between structural features and vis–NIR spectra of α-Fe2O3 hematite and AFe2O4 spinel oxides (A=Mg, Zn)

Iron (III) rich pigments MgFe2O4 and ZnFe2O4 spinel ferrites and α-Fe2O3 hematite were synthesized by Pechini route and precipitation process, respectively. The compounds were characterized by X-ray diffraction (XRD), Mössbauer spectroscopy and visible–NIR spectroscopy. Diffuse reflectance spectra were interpreted in regard of structural features of the three oxides in order to correlate absorption bands positions with structural parameters. It has been demonstrated that the two main absorption edges occurring in visible range (400–800 nm) can be attributed to two 2p(O2−)→3d(Fe3+) charge transfers, the energy being directly linked to the distortion degree of the [FeO6] octahedra.