Copper valency of superconducting phases in the Pb-doped Bi-Sr-Ca-Cu-O system

F. H. Chen*, H. S. Koo, S. C. Wu, Tseung-Yuen Tseng, S. R. Horng, M. F. Tai

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

Pb-doped Bi-Sr-Ca-Cu high-T c superconducting oxides have been prepared by a modified sol-gel process via the EDTA route. Upon decomposing the X-ray photoemission spectrum of the Cu 2p 3 2 core level of the superconducting oxide into three components Cu 1+ , Cu 2+ and Cu 3+ , we have found an obvious trend: the corresponding [Cu 1+ ]/[Cu 2+ ] ratio increased as more 110 K phase was formed in the sample. According to this trend, a defect model was proposed; it can reasonably explain some previous experimental results, such as a reduced oxygen atmosphere sintering, which effectively facilitates the formation of the 110 K phase, and the coexistence of copper and oxygen vacancies in Bi-system superconductors, observed by high-resolution transmission electron microscopy. On the other hand, the dimerization of holes in oxygen sites was also suggested to be a possible mechanism responsible for the increase in the ratio of [Cu 1+ ]/[Cu 2+ ].

Original languageEnglish
Pages (from-to)151-156
Number of pages6
JournalPhysica C: Superconductivity and its applications
Volume197
Issue number1-2
DOIs
StatePublished - 1 Jul 1992

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