CRITICAL-CURRENT DENSITY AND MICROSTRUCTURE OF C-AXIS-ORIENTED BI2SR2CACU2OX AND (BI, PB)2SR2CA2CU3OX SUPERCONDUCTING TAPES

The critical current density J(c) is investigated as a function of both field direction and temperature in c-axis-oriented Bi2Sr2CaCu2Ox ''2212'' and (Bi, Pb)2Sr2Ca2Cu3Ox ''2223'' polycrystals: a screen-printed ''2212'' tape with J(c) (77 K, 0 T) = 1.4 X 10(4) A/cm2, a screen-printed ''2223'' tape with J(c)(77 K, 0 T) = 1. 5 x 10(4) A /cm2 and a Ag-sheathed ''2223'' tape with J(c)(77 K, 0 T) = 2.2 x 10(4) A/cm2. The J(c) versus theta data at 77 K with the angle theta between B and the c-axis show that J(c) in a field is influenced only by the field component parallel to the c-axis. There is a correlation between the anisotropy ratio gamma=J(c)(B perpendicular-to c)/J(c)(B parallel-to c) and the half-height angular width DELTAtheta of a peak for B perpendicular-to c. An increase of B in a sample enhances gamma and narrows DELTAtheta. At fixed B, the screen-printed ''2212'' tape has the largest gamma and the narrowest DELTAtheta in all samples, which corresponds to the SEM result showing the highest c-axis alignment. The second highest is the screen-printed ''2223'' tape and the lowest is the Ag-sheathed ''2223'' tape. J(c) in zero field increases almost linearly with decreasing temperature below 70 K, which is explained by the flux creep model.