Oxidation State of Cobalt in the Na x CoO2-δ·yH2O Superconductor

Here we present results of accurate wet-chemical redox analyses revealing that the oxidation number of cobalt in the newly discovered CoO2-layer superconductor, Na x CoO2·yH2O (x ≈ 0.36, y ≈ 1.3) is ∼3.46. This value is significantly lower than the one (∼3.64) expected on the basis of the value dete...

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Bibliographic Details
Published in:Chemistry of materials 2004-05, Vol.16 (9), p.1693-1696
Main Authors: Karppinen, Maarit, Asako, Isao, Motohashi, Teruki, Yamauchi, Hisao
Format: Article
Language:English
Online Access:Get full text
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Summary:Here we present results of accurate wet-chemical redox analyses revealing that the oxidation number of cobalt in the newly discovered CoO2-layer superconductor, Na x CoO2·yH2O (x ≈ 0.36, y ≈ 1.3) is ∼3.46. This value is significantly lower than the one (∼3.64) expected on the basis of the value determined for the Na to Co stoichiometry ratio, x. The “lower-than-expected” value for the Co oxidation state may be alternatively explained by the presence of oxygen vacancies or excess protons. Moreover, the result implies that rather than an electron-doped CoIV lattice the phase should be considered as a hole-doped CoIII lattice.
ISSN:0897-4756
1520-5002
DOI:10.1021/cm035298h