Mo{sub x}Cu{sub 1-x}Sr{sub 2}YCu{sub 2}O{sub y} (0.3{<=}x{<=}1) revisited: Superconductivity, magnetism and the molybdenum oxidation state
- Dpto. Quimica Inorganica, Facultad de CC.Quimicas, U. Complutense de Madrid, 28040-Madrid (Spain)
- CNRS, Universite de Bordeaux, ICMCB, 87 avenue du Dr. A. Schweitzer, Pessac, F-33608 (France)
A systematic study is reported on the range of stability of molybdenum substituted Sr-based 123 compounds with Mo-Sr-Y-Cu system, synthesized under ambient pressure. All materials crystallize in the space group: P4/mmm and the observed solubility limit of Mo is rather low in this structure because secondary phases start to form as soon as x>0.3 in nominal composition is reached. The antiferromagnetic property in all superconducting multiphase samples can be attributed to the secondary phase Y{sub 2}Cu{sub 2}O{sub 5}. The influence of oxygen annealing on the changes in electronic structure for the pure Mo{sub 0.3}Cu{sub 0.7}Sr{sub 2}YCu{sub 2}O{sub y} system associated with a non-superconductor to superconductor transition has been investigated by means of X-ray photoelectron spectroscopy, powder X-ray diffraction, magnetic susceptibility and specific-heat measurements. We unambiguously show the predominance of the Mo{sup 5+} state over the Mo{sup 6+} one on both as-synthesized and annealed phases; annealing under an oxygen atmosphere enhances both the Mo{sup 6+} and Cu{sup 2+} amounts. We suggest that the enhancement of Mo{sup 6+} under oxygen annealing is in close relation with the decrease in the O 2p{yields}Cu 3d charge-transfer energy resulting in superconducting properties. - Graphical abstract: A study on the ambient-pressure synthesis and the range of stability of complex perovskites in the system Y-Sr-Cu-Mo shows that the solubility limit of Mo is rather low in this structure ({approx}30%). Secondary phases (detected by XRD) start to form for x>0.3 in nominal composition. All materials crystallize in the space group: P4/mmm. Antiferromagnetism in all superconducting multiphase samples is attributed to the secondary phase Y{sub 2}Cu{sub 2}O{sub 5}. Pure Mo{sub 0.3}Cu{sub 0.7}Sr{sub 2}YCu{sub 2}O{sub y} studied by means of powder X-ray diffraction, magnetic susceptibility and specific-heat measurements. Changes in electronic structure for the pure Mo{sub 0.3}Cu{sub 0.7}Sr{sub 2}YCu{sub 2}O{sub y} system associated with a non-superconductor to superconductor transition have been investigated by means of X-ray photoelectron spectroscopy (XPS). Highlights: Black-Right-Pointing-Pointer Solubility limit of Mo is rather low in Mo{sub x}Cu{sub 1-x}Sr{sub 2}YCu{sub 2}O{sub y} (x{approx}0.3). Black-Right-Pointing-Pointer Antiferromagnetism and superconductivity do not coexist. Black-Right-Pointing-Pointer Pure Mo{sub 0.3}Cu{sub 0.7}Sr{sub 2}YCu{sub 2}O{sub y} (T{sub c} Almost-Equal-To 30 K) prepared and characterized. Black-Right-Pointing-Pointer XPS shows that Mo{sup 5+} predominates over Mo{sup 6+}. Black-Right-Pointing-Pointer Annealing under O{sub 2} enhances Mo{sup 6+} and Cu{sup 2+} states.
- OSTI ID:
- 22012169
- Journal Information:
- Journal of Solid State Chemistry, Vol. . 191; Other Information: Copyright (c) 2012 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA); ISSN 0022-4596
- Country of Publication:
- United States
- Language:
- English
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