Critical current density improvement by intermediate deformation for the fabrication of Bi₂Sr₂Ca₂Cu₃O_10+δ/Ag round wires

Multi-filamentary Bi₂Sr₂Ca₂Cu₃O_10+δ/Ag round wires were fabricated by the powder-in-tube method. Both draw- ing and cold isostatic pressing methods were used to densify the filament cores of the Bi₂Sr₂Ca₂Cu₃O_10+δ/Ag round wires during intermediate deformation after the first heat treatment. Critical current measurements show that both methods can increase the self-field critical current density at 77 K. By optimizing the drawing process, the core density of the first heat treated round wires was increased significantly, resulting in a more than doubled critical current density improvement of the Bi₂Sr₂Ca₂Cu₃O_10+δ/Ag round wires. Increasing the drawing stress using a high strength metal sheath increased the critical current density further to about 1 × 10⁴ A/cm². By carrying out the intermediate deformation using the cold isostatic pressing method, the optimal critical current density was 8.6 × 10³ A/cm².