Microstructure, impurity content and critical current density in Nb3Sn

Abstract

Critical current density measurements, transmission electron microscopy and chemical analysis have established a correlation between critical current density J_c, the oxygen content in Nb₃Sn and the presence of a fine dispersion of precipitate. As the oxygen content increased from J_c increased from 1 to 6 × 10⁵ A cm⁻² at 46 kG. A fine precipitate (particle size similar 50 Å) was observed for all oxygen contents greater than 160 p.p.m. It is concluded that the precipitate particles act as flux-pinning centres in Nb₃Sn. No correlation was observed between nitrogen content and J_c.