Microstructure and current-voltage characteristics of bronze processed niobium tin composites

Bronze route conductors are widely used for high field purposes, To shift t heir limits to even higher fields it is decisive to understand the role tha t microstructure plays in controlling the current-voltage characteristic, M icrostructural properties of Nb3Sn are crucially determined by the reaction heat treatment. Therefore, several heat treatments on samples of a commerc ial composite were performed. The reaction temperatures extend from 600 deg reesC up to 750 degreesC, SEM micrographs were taken from filaments at diff erent positions within the samples. These micrographs were used to carry ou t a quantitative analysis of grain size. To investigate the connection of m icrostructural and electrical properties, resistive measurements of the cur rent-voltage characteristic at magnetic fields up to 15 T and 4.2 K were pe rformed.