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

✍ Scribed by F.H. Chen; H.S. Koo; S.C. Wu; T.Y. Tseng; S.R. Horng; M.F. Tai

• Publisher: Elsevier Science
• Year: 1992
• Tongue: English
• Weight: 414 KB
• Volume: 197
• Category: Article
• ISSN: 0921-4534
• DOI: 10.1016/0921-4534(92)90249-c

✦ Synopsis

Pb-doped Bi-Sr-Ca-Cu high-To 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 2pa/2 core level of the superconducting oxide into three components Cu ~+, Cu 2 + and Cu 3+, we have found an obvious trend: the corresponding [ Cu t+ ]/[Cu 2+ ] ratio increased as more I 10 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 ~ + ] / [Cu 2+ ].