On the phase formation in Ag and AgMg sheathed BSCCO (2223) tapes

BSCCO tapes with dispersion hardened AgMg sheaths possess excellent mechanical properties but reach commonly only about 70-80% of the critical currents of Ag sheathed reference tapes. Investigating the temperature dependence of I/sub c/ and the (2223) phase content for two annealing steps on 19 filamentary Ag and AgMg sheathed tapes, characteristic differences with respect to the reaction kinetics and the resulting final phase content were found. A detailed characterization of the properties of the AgMg envelope, defining the boundary condition during the tape annealing process, gives first indications, that the oxygen exchange between filament and annealing atmosphere is modified with obviously significant influence on the phase formation kinetics and phase diagram shifts.