Properties of a Fluorine-Doped Y-Ba-Cu-Oxide Superconductor Prepared by Hot-Pressing

Fluorine doped Y-Ba-Cu-oxide samples prepared by hot-pressing showed superconductivity without a subsequent heat treatment in oxygen, in contrast to the semiconducting behavior of undoped samples. CuF 2 powder was used as the fluorine source. Powders with the nominal composition YBa 2 Cu 3 O y F 0.2 were hot-pressed in oxygen atmosphere at 900–950°C; a density of 5.72–5.83 g/cm 3 was obtained. The Meissner effect was observed at 93 K and 75 K in the samples hot-pressed at 900°C and 950°C, respectively. The differing superconductivity between the undoped and F-doped samples may be due to changes in the average copper valence in the Y-Ba-Cu-O system.