OPTIMIZATION OF THALLIUM 1223 HIGH-TEMPERATURE SUPERCONDUCTING WIRE BY A SINGLE-STAGE COLD DEFORMATION PROCESS

Superconducting tapes containing (Tl0.5Pb0.5)Sr2Ca2Cu3O9 were manufactured by a powder-in-tube technique and a single annealing stage. The (Tl0.5Pb0.5)Sr2Ca2Cu3O9 forms a "1223" structure with a T(c) of over 120 K. A cold pressing stage was found to be necessary to achieve the higher J(c) values at 77 K. The transport J(c) was found to depend on: the annealing temperature, annealing time and pressing pressure. SEM examination of the Tl-1223 grain structure showed a marked difference between rolled and pressed tapes. This is ascribed to the production of a lead-rich phase during pressing, this is supported by XRD evidence. No significant degree of grain alignment was found in the Tl-1223 tapes, either by XRD analysis or by the measurement of transport critical current in applied magnetic fields.