Development of Bi-oxide superconducting tapes and coils

Abstract

We have developed Bi-2212 and 2223 tapes. For Bi-2212, two double stacked pancake type coils were fabricated using Bi-2212 Ag tapes prepared by a combination of the continuous dip-coating process and melt-solidification. A small coil (13 mm inner bore, 46.5 mm outer diameter) was inserted in a conventional superconducting magnet system. In a bias field of 20.9 T, the generated field of the coil was 0.9 T, at an I c of 310 A (criterion 10 −13 Ωm) at 1.8 K. Thus, the superconducting magnet system achieved the generation of a field of 21.8 T in the full superconducting state. A large coil (20 mm inner bore, 94 mm outer diameter) generated a field of 2.6 T ( I c = 385 A (10 −13 Ωm) ) at 4.2 K and 1.53 T ( I c = 225 A (10 −13Ωm) ) at 20 K in self-field. For Bi-2223, tapes were prepared by the powder-in-tube technique using Ag-10% Cu- x%M ( x = 0–1.0, M = Ti, Zr, Hf or Au) alloy sheaths. The high J c values of 5–7 × 10 4 A cm −2 at 4.2 K and 14 T were obtained for the tapes doped with x = 0.03–0.1 at.% Ti, 0.1 at.% Zr, 0.1 at.% Hf or 0.3% Au. These tapes have a modified Bi-2223 grain structure at the sheath/core interface and also a dense and more aligned microstructure, resulting in higher J c values.