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 properties of Ag-clad Bi-2223 tapes has been studied. Ag addition in the Bi-2223 tapes lowers the annealing temperature and accelerates the formation of 2223 phase. Ag is inert to the oxide core and exists as an isolated phase within the tape. However, its undesirable shape and large size cause grain misorientation and hence leads to a decrease of J(c). For Ag-sheathed Bi-2223 tapes, the critical strains for bend tests show a dependence on the tape thickness, the number of filaments and Ag/oxide volume ratio, attributable to the improved strength and flexibility of the special interfacial layer between Ag and oxides. The results of magnetoresistance and the V-I curves of a well defined tape after correction for the parallel conduction through the Ag-sheathing and the core show a similar behaviour as single crystals and the epitaxial thin films. The effective activation energy for the flux creep is larger than those for the single crystals and thin films. Long length Ag-sheathed Bi-based superconducting multifilamentary tapes up to 45 m have been 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. The fluctuation of I(c) along the length is less than 10%.