XANES and EXAFS study of Au-substituted YBa2Cu3O7-δ

The near-edge structure (XANES) of the Au L3 and Cu K edges of YBa2Au0.3Cu2.7O7-δ has been studied. X-ray diffraction suggests that Au goes on the Cu(1) site and XANES shows that this has little effect on the oxidation state of the remaining copper. The gold L3 edge develops a white line feature whose position lies between that of trivalent gold oxide (Au2O3) and monovalent potassium gold cyanide (KAu(CN)2) and whose intensity relative to the edge step is smaller than in the two reference compounds. The L3 EXAFS for Au in the superconductor resembles that of Au2O3. However, differences in the envelope of the Fourier filtered component for the first shell suggest that the local structure of the AU in the superconductor is not equivalent to Au2O3