Characterization of bulk and multifilamentary Nb3Sn and Nb3Al by diffractometric and resistive measurements

A series of bronze-processed Nb3Sn wires (binary and alloyed) and of powder metallurgically processed Nb3Al filaments were characterized by resistivity measurements. The composition profile across the layer was determined by Auger spectroscopy. Particular attention was given to the determination of the global composition profiles in both Nb3Sn and Nb3Al by means of diffractometric analysis in the stress-free state. The correlation between the lattice parameter and the chemical composition was the basis for a careful analysis of the shape of several strong diffraction lines. This relatively simple method gives a reliable picture of the overall composition profile. We have found that the indication of the average lattice parameter alone does not give a complete description of the real state of the layer because Bc2 is strongly correlated to variations in the composition. Therefore, the indication of the composition profile is necessary for understanding superconducting properties of the layers.