Binary and ternary niobium-base superconductors by the infiltration process

Two major interrelated focal points characterize this research. One was the decision to restrict the effort to A-15 compounds because of their superior critical temperatures and critical fields. The inherent brittleness of these compounds along with the requirement for a filamentary morphology led to the second focal point: a heavy reliance on a powder approach for the fabrication of superconducting tapes and wires. There were exceptions to the use of powder techniques where special circumstances such as the nature of a particular alloy system suggested an alternative approach. The quench-age technique described herein is an example of a nonpowder approach. Here the niobium-aluminum system is involved and the methodology is based on the fact that in a certain composition range a solid solution of aluminum in niobium is the stable phase at elevated temperatures, whereas at lower temperatures the stable phase is the desired A-15 compound. Additionally, niobium forms deformation twins which were found to be effective sites for the nucleation of the A-15 phase.