SUPERCONDUCTING PROPERTIES AND MICROSTRUCTURES OF BI-2223 AG-CU ALLOY SHEATHED TAPES DOPED WITH TI, ZR OR HF

Ag-Cu alloy doped with Ti, Zr or Hf have been used as sheath material for Bi-2223 superconducting tapes prepared by the powder-in-tube technique. Critical current density, J(c), was obtained to be 9.2 x 10(4) A/cm(2) at 4.2 K, 14 T and 3.4 X 10(4) A/cm(2) at 77 K, 0 T, which is 2-3 times larger than that of non-doped samples. A small amount of doping such as Ti, Zr or Hf of 0.03-0.1 at.% into Ag-10 at.% Cu alloy sheath enhanced growth of large plate-like grains, especially at interfaces between the Ag-Cu alloy sheath and oxide core. Furthermore, Bi-2223 phase alignment was significantly improved. These microstructural modifications are believed to be responsible for the improved high-J(c) property.