Emission Mössbauer spectroscopy in the Co–O system under high oxygen pressure Original Research Article

Results obtained by means of the emission Mössbauer spectroscopy in CoO and Co3O4 systems kept under relatively high oxygen pressure (air close to the normal pressure) are reported. Broadening of the 14.4-keV 57Fe Mössbauer line due to the diffusion of iron atoms in CoO has been investigated in the temperature range between 1275 and 1450 K. The excess of the linewidth caused by diffusive motions obeys the Arrhenius law with the activation energy of 1.86(8) eV. Mixed valence oxide Co3O4 was examined vs. temperature. Measurements were performed from the room temperature till 1073 K. Tetrahedrally coordinated iron impurities in the Co3O4 host lattice are in the high spin trivalent state despite that parent Co is divalent. The anharmonic contribution to the lattice vibrations at high temperatures was observed and analyzed for both CoO and Co3O4.