Influence of oxygen content on some properties of Nb sub(3)Sn tape used for superconducting transmission lines

The influence of the presence of oxygen in the Nb-Zr substrate upon some physical and mechanical properties of the Nb-ZrO sub(2) substrate and/or Nb sub(3)Sn tape superconductor prepared from such a substrate has been studied. The results have shown that the Nb sub(3)Sn grains are much finer in the case of Nb-ZrO sub(2), than those obtained on Nb-Zr substrate. As a result, both the electrical and mechanical properties have been substantially improved. The critical current at a field of 5T increased by between 100 and 200%, the alternating current losses decreased by about one order of magnitude, the tensile strength increased by about a factor of three and the microhardness value also increased by about a factor of three for oxygen contents in the range 0.03 to 0.70 wt%. The specific resistance of this substrate increased at the same time from 17 to 22 mu Omega cm and the relative elongation decreased from 5 to 3%.