SUPERCONDUCTING PROPERTIES OF YBA2CU3O7-AU COMPOSITES

By X-ray diffraction and photoelectron spectroscopy, we have demonstra ted that Au is incorporated in the YBCO lattice up to a concentration 0.1. An XPS study gave evidence for an electronic valence state Au1+. Its replacement in the Cu(1) site appears questionable due to the larg e difference in ionic radii (CU2+:0.073 nm; Au1+:0.137 nm). The so cal led 'irreversibility lines' determined by AC susceptibility measuremen ts are strongly affected by the doping. Up to the limit of solubility in the grains, an improvement in intra and intergrain coupling and flu x pinning energy is observed, showing the beneficial interest of YBCO- Au composites.