Abstract
Ba2Y1Cu3(O, F)7-δ compounds were prepared by solid-state reaction using BaCO3, Y2O3, CuO powders and one of BaF2, YF3 and CuF2⋅2H2O powders. It was found by thermal and X-ray analyses that YF3 was better fluoridized material to make the Ba2Y1Cu3(O, F)7-δ compounds compared with BaF2 and CuF2. Ba2Y1Cu3(O, F)7-δ compounds with a small amount of fluorine were a single phase with the orthorhombic structure like the Ba2Y1Cu3(O, F)7-δ compound. The superconducting transition temperature, Tc, and the lattice constants a0, b0 and c0 were slightly changed by adding the fluorine content. The Tc depends on the lattice constant. The maximum Tc was obtained for a sample with about 0.65 and 1.3 at % fluorine and a Tc onset was about 97K. The thermal stability of the Ba2Y1Cu3(O, F)7-δ compounds was increased compared with the Ba2Y1Cu3O7 compound.
