X-Ray Diffraction Studies of 2212-Type Superconductors in the Tl–Hg–Ba–Sr–Ca–Cu–O System

✍ Scribed by M. Valldor; Ph. Boullay; J. Axnäs; I. Bryntse

• Publisher: Elsevier Science
• Year: 2000
• Tongue: English
• Weight: 374 KB
• Volume: 153
• Category: Article
• ISSN: 0022-4596
• DOI: 10.1006/jssc.2000.8756

✦ Synopsis

Superconducting cuprates with the general stoichiometry (Tl, Hg) 2 (Ba, Sr) (Sr, Ca) 1 Cu 2 O 8؊ were examined by X-ray powder di4raction, including Rietveld re5nement calculations. The aim was to obtain structural properties that could be related to the diamagnetic transition onset temperature (T c(onset) ). R w values for nine di4erent samples, with di4erent Ba, Sr, and Ca contents, were 0.105 or less. For three of the polycrystalline samples, the diamagnetic transitions were con5rmed by resistivity measurements. Bond valence sum calculations indicate that T c(onset) increases (45+100 K) with a decreasing formal oxidation state of Cu in the superconducting plane. This tendency might be correlated with the apical distance between the (Ba, Sr) and Cu layers since the interplanar distance increases proportionally with the critical temperatures. In turn, this distance increases with the Ba/Sr ratio at the larger alkaline-earth metal site.