The role of grain boundaries in determining J c in high-field high-current superconductors

Abstract

The scaling laws that describe flux pinning in the two most common commercial superconductors, NbTi and Nb₃Sn made by the bronze process, are totally different. This is despite the fact the microstructural features that are responsible for flux pinning, sub-boundaries in NbTi and grain boundaries in Nb₃Sn, in both cases have concentrations of what in the bulk would be non-superconducting material. The only significant differences between the microstructures of the two materials is the morphology of the boundary structure. It is shown how this can lead to the two distinct pinning behaviours.