Chemical compositions at and near the grain boundaries in bronze-processed superconducting Nb3Sn

The chemical composition of bronze-processed Nb3Sn at grain boundaries and its variation as a function of distance from the grain boundary were determined using Auger electron spectroscopy. The composition at the grain boundary was 44.1, 30.6, and 25.4 at. % for Nb, Sn, and Cu, respectively, and approached to the bulk value (∼75 at. % Nb and ∼25 at. % Sn) at ∼20 Å into the grain, as determined by a depth-profiling method.