Transport, Magnetic, and SEM Characterization of a Novel Design Bi-2212 Strand

In this work, a new strand design for Bi-2212 conductors was studied. The new design had a single stack approach with randomly oriented but densely packed two-dimensional Bi-2212 filaments. This Bi-2212 Two-Dimensional Random-Oriented Single-Stack (2D-ROSS) Round Wire design led to high levels of grain texture and significant amounts of Ag-superconductor interface within the filaments, while maintaining a high strand fill factor. This new design was compared to a strand made with a conventional billet layout. Heat treatments were performed under 100% flowing oxygen, and the samples were melt processed at 884, 886, 888, and 89°C. The strands were studied via transport, magnetic, and electron optics techniques. The strands manufactured with the new process showed higher critical currents than the standard design strands in terms of engineering critical current density (J
_e
) but slightly lower layer critical current density (J
_c
). However both strand sets were limited by filament sizes which were not yet optimized and excessive C-content in the powders. J
_e
values of 48 A/mm
²
for the new strand design, and 26 A/mm
²
for the conventional double stack design, at 12 T and 4.2 K were observed. An interesting property of the new strand method was that the strands were less sensitive to small heat treatment, HT, temperature variations in terms of their final J
_c
properties. Magnetic and microstructure/phase assemblage studies observed less filament bridging in the new strand design as compared to the conventional one.