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Oxidation State of Cobalt in the NaxCoO2-d yH2O Superconductor

Maarit Karppinen·Isao Asako·Teruki Motohashi·Hisao Yamauchi
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Abstract

Here we present results of accurate wet-chemical redox analyses, revealing that the oxidation number of cobalt in the newly discovered CoO2-layer superconductor, NaxCoO2 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 presence of oxygen vacancies or excess protons. Moreover, the result implies that rather than an electron-doped Co(IV) lattice the phase should be considered as a hole-doped Co(III) lattice.

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Maarit Karppinen, Isao Asako, Teruki Motohashi, Hisao Yamauchi. 2004-02-18. Oxidation State of Cobalt in the NaxCoO2-d yH2O Superconductor. https://arxiv.org/abs/cond-mat/0402484

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