Oxidation study of iron by Mössbauer conversion electron and γ-ray scattering

Abstract

57Fe Mössbauer conversion electron and 14.4 keV γ-ray back-scattering have been applied to study the surface of oxidized iron samples. While γ-ray scattering explores a surface depth of about 10–20 μm, conversion electron spectra are indicative for the state of the Fe ion in the outermost surface layer up to about 3000 Å thick. Several oxide phases, like haematite, magnetite and wüstite, could be identified in the various oxide layers by their Mössbauer parameters. It is shown that the electron scattering technique is sensitive enough to allow a phase analysis and a kinetic study of oxide film growth at 500°C in an early stage, i.e. for oxidation times of the order of minutes, even if natural iron samples are used. Some examples demonstrate that due to the different depth-selectiveness of electron and γ-ray scattering spectra the combination of both techniques can give information about the type of oxide phases which are present in different surface depths.