Development of a Scalable Tl-1223 Tape Process -- Thallination of Powder Precursor Coatings

Superconducting tapes, 10-20 cm long, of TiBa2Ca2Cu3O9 on Ag have been fabricated by deposition of a thallium-free powder presursor on Ag followed by reaction with a thallium oxide vapor species. Single-sided and two-sided coatings are prepared using a spray-deposition or dip-coating, respectively. The coated tapes are annealed and then mechanically processed to densify the precursor. Continuousthallination of precursor tapes is performed by pulling the coated tape through a two-zone furnace at constant velocity and gave similar results as batch processing. Critical currents of the order 10-20 A at 77K, zero field for a 5 mm wide tape are observed. Properties as a function of magnetic field indicate reduced flux creep compared to the more anisotropic bismuth cuprate superconductors andmake thallium 1223 an attractive material for conductor applications at high temperatures.