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Phase formation and phase stability of KMnO4-treated (Na,K)CoO2.yH2O

Chia-Jyi Liu·C. -Y. Liao·S. Neeleshwar·Y. -Y. Chen·Chia-Jung Charlie Liu
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Abstract

We have first used the aquesous KMnO4 solutions to de-intercalate and oxideze gamma-phase of Na0.7CoO2 and successfully form the superconductive phase of cobalt oxyhydrate hydrates (Na,K)xCoO2.yH2O with Tc=3.2-4.6K based on the magnetization measurements. The higher molar ratio of KMnO4/Na used to treat Na0.7CoO2 results in more removal of Na+ and leads to a partial or even complete replacement of K+ for Na+. The low molar ratio of KMnO4/Na forms a superconductive phase with the c-axis ca. 19.6 angstrom, whereas the high molar ratio of KMnO4/Na forms a non-superconductive phase with teh c-axis ca. 13.9 angstrom. The superconductive 19.6 angstrom phase is unstable with respect to the ambient air in terms of losing water molecule from the structure; nevertheless, the dehydration/hydration process is reversible when storing the sample in a chamber with sufficient humidity.

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Chia-Jyi Liu, C. -Y. Liao, S. Neeleshwar, Y. -Y. Chen, Chia-Jung Charlie Liu. 2007-05-11. Phase formation and phase stability of KMnO4-treated (Na,K)CoO2.yH2O. https://arxiv.org/abs/cond-mat/0407420

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