Structural analysis of the charge transfer mechanism in the superconducting compounds Pb2Sr2Y1−xCaxCu3O8+δ
| Autor: | C. Chaillout, J.L. Tholence, J.J. Capponi, Omar Chmaissem, M. Marezio |
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| Rok vydání: | 1993 |
| Předmět: |
Superconductivity
Diffraction Microprobe High-temperature superconductivity Valence (chemistry) Mechanical Engineering Metals and Alloys chemistry.chemical_element Copper law.invention Crystallography chemistry Mechanics of Materials law X-ray crystallography Materials Chemistry Single crystal Nuclear chemistry |
| Zdroj: | Journal of Alloys and Compounds. 195:169-172 |
| ISSN: | 0925-8388 |
| DOI: | 10.1016/0925-8388(93)90712-v |
| Popis: | Pb 2 Sr 2 Ln 1−x Ca x Cu 3 O 8+δ is one of the copper-based superconductors with high critical temperature. Undoped Pb 2 Sr 2 YCu 3 O 8 is not a superconductor and becomes so when some of the trivalent Y cations are replaced by bivalent Ca cations. Microprobe analysis and magnetic measurements have been carried out on several single crystals. The x Ca values are found to be between 0 and 0.42, while T c varies between 0 and 80 K. Structural determinations by X-ray diffraction (6 crystals) show that the introduction of calcium reduces the stress between the CuO 2 and SrO layers. The Y substitution with Ca increases the valence of Cu(2) cations with no appreciable variation of the apical distance Cu(2)-O(1). The oxidation of substituted compounds is accompanied by the suppression of the superconducting state because of the movement of the O(1) atoms towards the Pb 4+ cations and away from the Cu(2) ones. This mechanism of charge transfer is very different from that of YBa 2 Cu 3 O 7−x . |
| Databáze: | OpenAIRE |
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