Electronic States of Cobalt Ions in EuBaCo2O5 + δ Layered Cobaltites

JETP Letters - The oxygen K-edge X-ray absorption spectra in EuBaCo2O5.52 ± 0.02 and EuBaCo2O5.24 ± 0.02 cobaltites are measured at temperatures of 300 and 440 K, which are below and...     

Erratum to: Several Articles in JETP Letters Published Online First

JETP Letters - An Erratum to this paper has been published: https://doi.org/10.1134/S0021364022330013     

Determination of charge states of cobalt ions in nanostructured GdBaCo2O5.5 cobaltites by means of X-ray absorption spectroscopy

Physics of the Solid State - X-ray absorption spectroscopy has been applied for a characterization of charge states of cobalt ions of nanostructured GdBaCo2O5.5 complex oxides. The analysis of...     

Soft X-ray absorption spectroscopy of titanium dioxide nanopowders with cobalt impurities

The charge states of the cobalt ions in TiO₂ nanopowders with the anatase lattice are studied by soft X-ray absorption spectroscopy. It is found that, at a low cobalt impurity concentration (1.8 at %), the cobalt ions with an oxidation state 2+ are mainly located in the tetrahedral (T _d ) environment of oxygen ions. Amorphous titanium dioxide exists on the sample surface before heat treatment. Annealing in vacuum or hydrogen leads to the enrichment of the nanoparticle surfaces with Co²⁺ ions, a change in the coordination of the remaining part of cobalt ions from octahedral to tetrahedral, stabilization of the anatase structure, and the disappearance of the amorphous phase. The crystal lattice of the samples with a relatively high cobalt concentration (12 at %) is distorted, and annealing does not cause the disappearance of the amorphous phase of TiO₂. Cobalt is reduced to its metallic state upon hydrogen annealing of the samples with a high cobalt concentration.