Application of X-ray absorption spectroscopy to the investigation of charge states of iron ions in iron borate nanoceramics

Abstract

The method of X-ray absorption spectroscopy has been used for the investigation of charge states of iron ions in iron borate nanoceramics prepared by shear deformation under pressure. The experimental Fe 2p X-ray absorption spectra have been presented in comparison with the calculation of atomic multiplets of iron ions taking into account the charge transfer from the 2p orbitals of oxygen to the 3d orbitals of iron and the crystal-field splitting of the 3d orbitals of iron. Our results indicate that, in addition to iron ions in the ground charge state Fe3+, nanostructured FeBO3 contains a few percent of Fe2+ ions. It has been found that an increase in the degree of plastic deformation (the rotation angle of the anvils) leads to a decrease in the size of crystallites and to an increase in the concentration of Fe2+ ions without the formation of new phases. The results of this work agree with the magnetic and optical measurements and confirm high defectness of FeBO3 nanoceramics.