Pb-1212系酸化物高超伝導体における(Pb,Cu)O層への元素置換効果と酸素不定比性

概要

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The Pb site in the (Pb, Cu)O layer of the Pb-1212 oxide superconductor (Pb0.75Cu0.25)Sr2(Y0.5Ca0.5)Cu2O7+z is partially substituted by metals M=Li, Bi, In, Sn, and Sb. The Bi substitution at 5 mol% markedly depresses the superconductivity, whereas the substitution by Sb and In raises the superconducting critical temperatures for the electrical resistivity and the ac magnetic susceptibility. The thermogravimetric analysis reveals an enhancement of oxygen deficiency in the Bi-substituted sample. The iodometric titration confirms the large amount of oxygen defect which causes decrease in the hole concentration on the Bi substitution. The hole doping by the substitution with Sb and In appears to be efficient because of the lower ionic valence of these cations and the increased oxygen content in the samples.
九州大学の論文