EXAFS and XANES spectra at the edges of Cu and Y have been measured in the YBa2Cu3O9-δ(δ 2) superconductor. The oxygen coordination around the two metals is found to generally agree with the model suggested by diffraction experiments, especially as the occurrence of two distinct distances between Cu and O along the perovskite structure c-axis is concerned. Conversely, some evidence is found for a partial occupation of the oxygen sites in the yttrium plane, a result excluded by diffraction experiments. This is better supported by EXAFS spectra at the Y-edge. The XANES spectra of the superconductor are remarkably different from those of Cu oxides suggesting the presence of both divalent and trivalent Cu, in agreement with EXAFS and diffraction results.

Atomic Local Coordinations and Multivalent States in YBa2Cu3O9-δ Superconductors / G. M., Antonini; CALANDRA BUONAURA, Carlo; Corni, Federico; F. C., Matacotta; M., Sacchi. - In: EUROPHYSICS LETTERS. - ISSN 0295-5075. - STAMPA. - 4(1987), pp. 851-856.

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