Tl-1223 conductors have been fabricated by the powder-in-tube (PIT) and surface-coated conductor (thick film) techniques. Current densities (J/sub c/) of 20,000 A/cm/sup 2/ and 12,000 A/cm/sup 2/ have been achieved at 77 K in short monofilament tapes and meter-long 37-filament tapes respectively. A large diameter test pancake coil was successfully fabricated with 17 m long PIT tapes. A new process has been developed to achieve grain alignment in PIT Tl-1223. Critical currents of 18 A and a J/sub c/ of 19000 A/cm/sup 2/ has been achieved at 77 K in surface-coated Tl-1223 conductor fabricated by an industrial process.

Optimum thermomechanical processing conditions have been developed to achieve a high current density in powder-in-tube (PIT) thallium-based (Tl,Pb)-1223 and (Tl,Bi)-1223 tapes. Critical currents in excess of 25 A corresponding to a current density of 20 000 A/cm2 have been achieved in these tapes at 77 K. Heat treatment and intermediate deformation sequences, heating rates, and starting precursor phase assemblages have been examined to optimize the current density. A combination of processing conditions that result in incremental densification, less microcracking and liquid formation in the early and final stages of thermomechanical treatment is found to result in the highest current densities.