Multifilamentary Superconducting Composites

Abstract

Multifilamentary composite superconductors started becoming available in the 1970s. These are niobium based (Nb-Ti and Nb₃Sn) superconductors. The record high temperature at which a material became superconductor was 23 K and was set in 1974. In 1987, there started appearing reports of superconductivity at temperatures up to 90 or 100 K in samples containing lanthanum, copper, oxygen, and barium or another Ha metal. These new ceramic superconductors have layered perovskite body-centered tetragonal structure and, not surprisingly, are very brittle. There remains an extremely large gap to be bridged between producing a small sample for testing in the laboratory and making a viable commerical product. The Nb-Ti system took 15–20 years between the discovery and the commercial availability. The new high-temperature oxide superconductors hold a great promise and it is quite likely eventually they will also be made into some kind of composite superconductors. Thus, it is quite instructive to review the composite materials aspects of niobium based superconductors. But first a short introduction to the subject of superconductivity is in order.