Miscibility of Au and Cu in superconducting YBa2(Cu1-xAux)(3)O7-delta for 0 < x < 0.15

Au has been successfully incorporated into the 123 superconducting oxide YB a2(Cu1-xAux)(3)O7-delta with up to 15% of the Cu sites occupied by Au atoms (n = 0.15). Earlier work found an apparent solubility limit of only 3.3%. Higher Au concentrations in these sintered ceramics were readily obtained b y substituting Au2O3 for the corresponding amount of CuO in the starting po wders, instead of adding metallic Au to stoichiometric 123 mixtures. Au is the only known dopant which raises the superconducting transition temperatu re of the 123 copper oxide, by 1.5 K for x approximate to 0.03. Increasing Au concentrations cause a gradual drop in T-c,. More than a "doped" copper oxide, at these concentrations YBa2(Cu1-xAux)(3)O7-delta is a novel, contin uous Cu-Au oxide system. (C) 1999 Elsevier Science B.V. All rights reserved .