Effects of Substitution by Sc on Superconductivity and Chemical Structures in Y–Ba–Cu–O Systems

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Abstract
The electrical conduction and chemical properties in Y–Ba–Cu–Sc oxide systems in which Sc was partially added in place of Y or Cu were investigated. These systems show a high-T c superconductor-semiconductor transition with increasing Sc concentration. The superconducting samples are in the orthorhombic phase of the 123 compounds with unidentified structures which grow with increasing Sc concentration. Photoemission studies reveal that the Cu core-level spectra in the superconducting phase consist of bivalent and trivalent states, whereas the monovalent state becomes evident in the semiconducting phase. It was found that the T c's of the systems correlate well with the average valence of Cu ions.