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| Na-site substitutions were performed in cobalt oxyhydrate superconductor using an ion-exchange post treatment, with the various exchanging ions. The ion-exchange reaction with Li＋, K＋, and NH4＋ ions resulted in the destruction of the bilayer hydrate structure. Meanwhile, the ion-exchanges with Mg2+, Ca2+, Sr2+ and Ba2+ ions were successful. The incorporation of alkaline-earth ions was found to be related to the similarity in size between the guest ion and the host one. About half of the sodium was replaced by calcium. The substituted bilayer hydrates were all superconductors with the Tc from 3.1 to 4.5 K. |
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| Keywords:Cobalt Oxyhydrate Superconductor, Substitution, Ion exchange |
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