The fabrication and thermomechanical processing of Ag/Bi-2223 jelly-roll wires

For this feasibility study, silver/superconductor jelly-roll samples with a superconductor composition of Bi1.8Pb0.4Sr2Ca2Cu3Ox (2223), were fabricated via a thick-film processing technique. It was found that the densification and alignment of 2223 grains along the Ag layers was crucial to achieving high critical current densities (Jc). The effects of cyclic mechanical working and heat treatment were investigated to develop a scheme to maximize Jc. The highest zero-field J0 value of 2650 A cm-2 (Ic = 43 A) was obtained in a jelly roll heat treated at 815 degrees C, where the majority of the mechanical deformation was performed prior to the first heat treatment. Magnetic-field-dependence measurements made in a 50 G field showed a 23% reduction in Jc when the field was applied parallel to the current flow, and a 30% reduction when the field was applied perpendicular to the current flow. This was superior to the best comparable powder-in-tube samples. (author)