Engineering critical current density improvement in Ag-Bi-2223 tapes

Ag alloy sheathed Bi-2223 multifilament tapes were produced by the powder-i n-tube method. Engineering critical current density improvement has been ac hieved through both enhancement of critical current density by control of t he thermal behavior of oxide powder and by an increase of the filling facto r of the tapes. Phase evolution at initial sintering stage has been studied by a quench experiment in Ag-Bi-2223 tapes. The content, texture, and micr ostructure of various phases were determined by XRD and SEM, A novel proces s approach has been invented in which square wire was chosen rather than ro und wire as a preform prior to the flat rolling that achieved more homogeno us filament distribution, Filament geometry and density were simulated by F inite Element Modeling. The tapes with large filling factor up to 45 % have been produced with a hard metal outer sheath, which facilitates the superc onductor composite sustaining large proportional oxide ceramics in the comp osite during drawing and rolling process. By optimization of the thermal an d mechanical process, a J(c) of 12 kA/cm(2) has been achieved in a 0.18x3.1 mm(2) size tape which carried 67 A.