| Autor: |
Zetterer, T., Otto, H. H., Lugert, G., Renk, K. F. |
| Zdroj: |
Zeitschrift für Physik B Condensed Matter; September 1988, Vol. 73 Issue: 3 p321-328, 8p |
| Abstrakt: |
We report on a comparative crystal chemical study of the Tl2-xBa2CanCun+1O2n+6(n=0, 1, 2) high-Tc superconductors. Superconducting properties were determined by DC-conductivity and-susceptibility measurements. An X-ray diffraction analysis reveals the nonstoichiometry of the compounds as a link between structural and superconducting behavior. A comparison of the different structures gives evidence that T1 deficiency in the TlO double layers increases with increasingn; this deficiency causes apparent Cu valences larger than 2+in the superconducting phases thus maintaining the charge balance. By extracting appropriate chemical formulas and performing a bond strength calculation we obtained the mixed-valent oxidation state of copper for the superconducting tetragonal phases as being 2.17+(n=0), 2.25+(n=1) and 2.31+(n=2) respectively; for the non-superconducting orthorhombic phase Tl2-xBa2CuO6-y a Cu valence of about 2+is suggested. |
| Databáze: |
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