EFFECT OF SILVER ON THE PROCESSING AND PROPERTIES OF BI-2223 AG TAPES

The effect of Ag addition and Ag sheath on the processing and properti es of Ag-clad Bi-2223 tapes has been studied. Ag addition in the Bi-22 23 tapes lowers the annealing temperature and accelerates the formatio n of 2223 phase. Ag is inert to the oxide core and exists as an isolat ed phase within the tape. However, its undesirable shape and large siz e cause grain misorientation and hence leads to a decrease of J(c). Fo r Ag-sheathed Bi-2223 tapes, the critical strains for bend tests show a dependence on the tape thickness, the number of filaments and Ag/oxi de volume ratio, attributable to the improved strength and flexibility of the special interfacial layer between Ag and oxides. The results o f magnetoresistance and the V-I curves of a well defined tape after co rrection for the parallel conduction through the Ag-sheathing and the core show a similar behaviour as single crystals and the epitaxial thi n films. The effective activation energy for the flux creep is larger than those for the single crystals and thin films. Long length Ag-shea thed Bi-based superconducting multifilamentary tapes up to 45 m have b een fabricated using powder-in-tube technique. A I(c) up to 15 A and J (c) of 8500 A/cm2 at 77 K over the entire length has been achieved. Th e fluctuation of I(c) along the length is less than 10%.