Superconductivity in Oxyfluorides of the Type Ba sub 2 RCu sub 3 O sub (x) F sub (y) (R=Y, Eu)

Oxyfluorides of the type Ba sub 2 RCu sub 3 O sub (x) F sub (y) are prepared by the reaction of Ba sub 2 RCu sub 3 O sub (7-delta) (0=delta=1) with fluorine gas at temperatures between 200-500C. Fluorinated samples are single phase as determined by x-ray diffraction. The oxygen and fluorine stoichiometries are determined by a combination of iodometric titration, fluoride ion selective electrode analysis and TGA methods.