Superconducting Tl(1223) tapes prepared by in-situ reaction under high pressure

Superconducting Tl(1223) tapes were produced by the powder-in-tube technique from a mixture of precursors in Ag(Au) tubes. High-purity ceramics (> 95% TI(1223), T-c similar to 120 K) were obtained by an in-situ reaction under high helium pressure. A critical current density of 10'000 A/cm(2) at 77 K was reached for (Tl,Pb,Bi)(Sr,Ba)(2)Ca2Cu3O9-delta tapes prepared at 50 bar. For samples treated at 2 kbar the magnetic-field dependence was reduced, the critical current density at 0.2 T being decreased by a factor between 12 and 16, with respect to the value at 0 T. Increasing the reaction time and the pressure had a positive effect on the grain size and the density, respectively.