Study on thermo-mechanical treatment in fabrication of Bi2212/Ag HTS wire

Round shape Bi2212/Ag wire is isotropic, while Bi2212/Ag or Bi2223/Ag tape has anisotropic characteristics or performances with respect to magnetic field orientation, which is the only HTS wires that can be used to make Rutherford cable to transport high current. In this work, two different Bi2212/Ag round wires with different Ag ratio were fabricated using powder-in-tube method and processing factor at each step was investigated. Double stacked 385 (55 × 7) filamentary wires of various final diameter were heat treated at different melting temperatures. Microstructure after pre-annealing was investigated. Wires which have Ag ratio (silver area/superconductor area) of 0.3 and 0.42 after powder filling show similar critical current density. Higher Ag ratio wire at 0.74 mm diameter heat treated at melting temperature 890 °C shows critical current density of 2750 A/mm2 at 4.2 K, 0 T.