RECENT ADVANCES IN BISMUTH-BASED SUPERCONDUCTORS

Significant progress has been made in the development of high-critical-temperature (high-T-c) mono- and multifilament bismuth-based superconductors by the powder-in-tube (PIT) technique. High critical current density (J(c)) has been achieved in both short- and long-length monofilament conductors. J(c)s up to 1.2 x 10(4) A/cm(2) were achieved in an 850 m long multifilament conductor. Pancake-shaped coils and test magnets, fabricated from long conductors, were characterized at various temperatures and applied magnetic fields. One such magnet containing 480 m of high-T-c tape generated a record-high field of 2.6 T at 4.2 K. Multifilament conductors appear to possess better mechanical properties and retain a higher percentage of their initial critical current under strain than monocore conductors, which is important for practical considerations. PIT processing of superconducting tapes with AgAl2O3 as the sheath material is perhaps another route to improve mechanical properties.