ENHANCEMENT OF CRITICAL-CURRENT DENSITY AND STRAIN TOLERANCE IN AG-SHEATHED BSCCO-(2223) TAPES BY CONTINUOUS SILVER REINFORCEMENT

We have used a modified powder-in-tube technique in various configurat ions to demonstrate significant improvement in the transport propertie s and strain tolerance of Ag-sheathed BSCCO superconducting tapes. In this process, the BSCCO core has been reinforced with a silver rod pla ced concentrically within the silver tube and then processed into appr oximate to 250 mu m thick tapes by established metal-working technique s. A noticeable improvement in critical current density, J(c), was obs erved as a result of this modification. This increase is attributed to increased texturing, decrease in thickness of BSCCO layers, increase in the length of the Ag/BSCCO interface, and decrease in the volume fr action of the superconducting core which is less effective in contribu ting towards the overall critical current of the tape. Further improve ments have been made to this configuration by incorporating another ri ng of superconductor into the core. The improved configurations led to a significant increase in J(c) over that of monolithic BSCCO tapes. C ritical current densities of Fs:40 kA cm(-2) at 77 K and self-field ha ve been consistently achieved in 150 mu m thick tapes after 150 h of s intering. Analysis of critical current through various sections of the tape indicates that 80% of the critical current is carried by the cen tre section of the core within which the Ag rod is located. The bend s train tolerance of the tapes containing a silver core was found to be significantly better than that of the monolithic tapes. At an applied surface bend strain of 1.0%, about 98% of initial J(c) was retained in Ag-reinforced tapes, compared with only 54% in monolithic tapes.