Oxygen Intercalation Homogeneity and Electrical Transport in Superconducting Ba sub 2 YCu sub 3 O sub (7-delta) crystals.

The intercalation of oxygen in twinned single crystals of Ba sub 2 YCu sub 3 O sub {7- delta} occurs by diffusion along basal ab planes, as shown by time-dependent resistivity measurements at elevated temperatures. Separation of the oxygen-deficient 60K phase in crystals annealed in O sub 2 is revealed by an anomalous resistance along the c direction below T sub c. Susceptibility analysis shows that oxygenation and the sharpness of the superconducting transition can be enhanced significantly, with no change in T sub c, by F-ion implantation followed by re-diffusion of oxygen.