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

Bronze route conductors are widely used for high field purposes. To shift their limits to even higher fields it is decisive to understand the role that microstructure plays in controlling the current-voltage characteristic. Microstructural properties of Nb/sub 3/Sn are crucially determined by the reaction heat treatment. Therefore, several heat treatments on samples of a commercial composite were performed. The reaction temperatures extend from 600/spl deg/C up to 750/spl deg/C. SEM micrographs were taken from filaments at different positions within the samples. These micrographs were used to carry out a quantitative analysis of grain size. To investigate the connection of microstructural and electrical properties, resistive measurements of the current-voltage characteristic at magnetic fields up to 15 T and 4.2 K were performed.