Fabrication of Ag-sheathed Bi-superconducting tapes and coils
Ag-clad (Bi,Pb)/sub 2/Sr/sub 2/Ca/sub 2/Cu/sub 3/O/sub 10+z/(2223) multifilament tapes up to 46 meters have been fabricated using powder-in-tube technique. A I/sub c/ of 15 A at 77 K over the entire length has been achieved with a fluctuation along the length less than 10%. Coils up to 306 turns with a I/sub c/ of 45.6 A at 4.2 K were produced through reaction and winding procedure using multifilament tapes. J/sub c/ versus phase formation, degree of texture and grain growth of Ag-sheathed Bi-based superconducting tapes have been investigated during thermomechanical processes. The initial modest increase in J/sub c/ is attributable to the increase of 2223 phase and grain alignment, while in second stage grain growth is mainly responsible for a rapid increase of J/sub c/. Prolonged annealing in the third stage results in recrystallisation of the large grains, and hence a decrease in J/sub c/. A I/sub c/ of 8 A at 77 K and 67 A at 4 K and zero field has been achieved for Ag-clad Bi/sub 2/Sr/sub 2/CaCu/sub 2/O/sub 8+z/(2212) tape using a partial melting and atmosphere-controlled process.<<ETX>>