High-Tc superconductivity in three-fluorite-layer copper oxides.: II.: (Cu,Mo)Sr2(Ce,Y)3Cu2O11+δ -: art. no. 174515

We have synthesized high-quality samples of the s=3 member of the (Cu,Mo)-12s2 homologous series of layered copper oxides. The (Cu,Mo)-1232 phase forms as a single phase for the cation composition (Cu0.75Mo0.25)Sr-2(Ce0.67Y0.33)(3)Cu2O11+delta through solid-state synthesis in air, but the samples as synthesized are not superconductive. Superconductivity is induced in the air-synthesized samples by means of high-pressure oxygenation carried out at 5 GPa and 500degreesC in the presence of Ag2O2 as an excess oxygen source. With increasing ratio of Ag2O2 to the (Cu,Mo)-1232 phase the c-axis lattice parameter gradually decreases and T-c increases. The highest T-c value of 53 K reached for samples oxygenated in the presence of 100 mol% Ag2O2 exceeds the values reported for Cu-based two-fluorite-layer compounds.