Bulk Superconductivity at 60K in Oxygen-Deficient Ba sub 2 YCu sub 3 O sub (7-delta) and Oxygen Isotype Effect in La sub (1.65) Sr sub (0.15) CuO sub 4.

Oxygen deficient polycrystalline samples of Ba sub 2 YCu sub 3 O sub (7-delta) have been prepared by a Zr-gettered annealing technique. A distinct bulk superconducting phase with a T sub c of 60K is found for 0.30.4, which has partial ordering of the vacancies in the Cu-O chains. This ordering is seen in electron diffraction studies and also in both the value and the temperature dependence of the electrical resistivity. Isotype effect studies La sub (1.85) Sr sub (0.15) CuO sub 4 have been performed by partially substituting sup 18 O for sup 16 O. Raman spectroscopy confirms the expected frequency shift of the 428 cm sup (-1) phonon line and T sub c is found to decrease.