Enhancing the engineering J/sub c/ of Bi-2223 multifilamentary tapes by two-axial rolling and periodic pressing

Bi-2223 multifilamentary tapes with a filling factor from 20 to 51% have been produced by a modified Powder-In-Tube method, where a two-axial rolling method is used to replace the standard drawing process. Because the two-axial rolling process does not apply tensile force during wire fabrication and every filament receives a very similar reduction during the deformation processing of the wire into a tape, the size homogeneity of filaments can be significantly improved for tapes with high filling factor. Combining this with a periodic pressing process, the engineering critical current density has been increased from 4 to 8 kA/cm/sup 2/ (77 K, 0 T) for tapes with a filling factor of 35%. The effect of deformation and heat-treatment conditions on the microstructure and transport properties has been found to be quite different in tapes with high filling factor.