Fabrication of Ag-sheathed Bi-superconducting tapes and coils

摘要

Ag-clad (Bi,Pb)2Sr2Ca2Cu3O10+z(2223) multifilament tapes up to 46 meters have been fabricated using powder-in-tube technique. A Ic 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 Ic of 45.6 A at 4.2 K were produced through reaction and winding procedure using multifilament tapes. Jc 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 Jc 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 Jc. Prolonged annealing in the third stage results in recrystallisation of the large grains, and hence a decrease in Jc. A Ic of 8 A at 77 K and 67 A at 4 K and zero field has been achieved for Ag-clad Bi2Sr2CaCu2O8+z(2212) tape using a partial melting and atmosphere-controlled process.