Development of Tl-1223 superconducting tapes

A superconducting tape based on the TlBa 2Ca 2Cu 3O 9 (Tl-1223) phase sheathed in silver was fabricated using the powder-in-tube method. Optimal conditions to synthesize powder ( T c =110 K) and anneal composite tapes were examined. Microstructural examination indicates that cracks are easily healed during a 3 h anneal at the relatively low temperature of 775°C. A transport critical current density J c of 6200 A/cm 2 at 75 K was measured on short lengths of the annealed rolled and pressed 0.20 mm thick tape. The J c value drops to about 250 A/cm 2 at 75 K and 1 T due to the presence of weak links; however, a J c of 1000 A/cm 2 at 45 K is maintained constant to above 6 T. Measurements of magnetic hysteresis loops indicate that the Tl-1223 tape exhibits a high degree of flux pinning. Very little texturing of the superconducting core was evident.