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

X-ray Diffraction and X-ray Spectroscopy Studies of Cobalt-Doped Anatase TiO2:Co Nanopowders

“…It is necessary to clarify the charge state of cobalt ions in Co-doped anatase TiO 2 nanopowders subjected to annealing in vacuum or hydrogen. According to our X-ray spectroscopy experiments, tetrahedrally coordinated cobalt ions are in the 2+ oxidation state in all the Ti 0.97 Co 0.03 O 2 samples, which is in agreement with the recently reported results of X-ray absorption studies on Ti 0.98 Co 0.02 O 2 . However, X-ray diffraction data and results of the hard X-ray absorption spectroscopy measurements on the annealed samples indicate emergence of metallic cobalt.…”

“…It allows us to propose a novel mechanism of exchange interaction, e.g., one based on Rudermann–Kittel–Kasya–Yosida type (RKKY). We have found at the base of our X-ray diffraction and soft X-ray absorption spectroscopy measurements that cobalt ions are tetrahedrally coordinated by oxygen ions …”

“…According to our X-ray spectroscopy experiments, tetrahedrally coordinated cobalt ions are in the 2+ oxidation state in all the Ti 0.97 Co 0.03 O 2 samples, which is in agreement with the recently reported results of X-ray absorption studies on Ti 0.98 Co 0.02 O 2 . 18 However, X-ray diffraction data and results of the hard X-ray absorption spectroscopy measurements on the annealed samples indicate emergence of metallic cobalt. The controversy between these results can be resolved if we take into account information depth of our experiments.…”

“…We have found at the base of our X-ray diffraction and soft X-ray absorption spectroscopy measurements that cobalt ions are tetrahedrally coordinated by oxygen ions. 18 In this work, we report the X-ray diffraction data, soft and hard X-ray absorption spectra, and resonant inelastic X-ray scattering spectra of TiO 2 :Co nanopowders before and after heat treatment for the first time. The soft X-ray absorption spectra have been compared with calculations of atomic multiplets taking into account the crystal field effect.…”

Dehydration of Electrochemically Protonated Oxide: SrCoO2 with Square Spin Tubes

“…Together with the topochemical nature of the reaction, these observations led us to conclude the composition to be SrCoO 2 , meaning that the dehydration reaction (HSrCoO 2.5 → SrCoO 2 + 0.5H 2 O) occurs. Comparison of the calculated absorption spectra of the Co L-edge shows that the experimental spectrum is closest to tetrahedral rather than octahedral 35 and square-planar 36,37 coordination (Figure 3c). The tetrahedral geometry of Co 2+ (d 7 ) appears to be favorable in terms of the crystal field stabilization energy.…”