Bi-System Oxide Superconducting Tapes Based on Silver-Alloy for Power Current Leads

To investigate stabilized materials in contact with oxide superconductors for current lead, the electrical resistivity and thermal conductivity of Ag-alloy samples were measured. Measured values obtained for the Ag-Au alloys showed a strong influence by Au content at low temperature, while those for Ag-Cu alloys showed a weakly depends on Cu content. Superconducting tapes of Bi-2212 and Bi-2223 stabilized with the alloys mentioned above were prepared. The critical current density Jc of the tapes were measured by the four-probe method. A strong dependence of Jc degradation on Cu content was recognized, but, no influences by Au could be observed. Values q(Heat input per critical current at low temperature end 4.2K) were calculated to evaluate the materials as for current lead use. The Ag-Au alloy sheathed superconducting tapes can impede heat flow with a q values smaller by 2 digits than the copper leads even though a magnetic field is present around 77K.