Effect of silver on phase formation and superconducting properties of Bi-2223/Ag tapes

摘要

The effect of Ag on the phase formation and superconducting properties of Ag-clad Bi-2223 tapes has been studied. TEM studies reveal that the grains adjacent to the Ag-sheath are nearly single 2223 phase with their c-axis perpendicular to the Ag-sheath, but in the interior of the superconductor core, an intergrowth of the 2223/2212 polytypoids within the grain and misalignment become evident. Ag addition in the Bi-2223 tapes lowers the annealing temperature and accelerates the formation of 2223 phase. However, its undesirable shape and large size cause grain misorientation and hence leads to a decrease of J/sub c/. The improvement in bend strain is attributable to the interfacial layer adjacent Ag sheath. The results of magnetoresistance of a well defined tape after correction for the parallel conduction through the Ag-sheath and the core show that the effective activation energy for the flux creep is larger than those for the single crystals and thin films. But the dissipative behaviour is similar to single crystals and the epitaxial thin films.