Demonstration of better superconducting performance in a solder with low lead content

Abstract

Lead-free SnIn solders are promising for superconducting magnet applications. However, their superconducting properties are not as good as lead solders. In order to improve the superconducting performance of the Sn–In solders, researchers have investigated the superconducting properties of ternary systems such as Sn–In–Bi for solder joints. In this study, powders of Pb, Nb, AgCu and grapheme nano pellets in the ratios of 0.5–5 wt% have been added into SnIn (35:65) to investigate their microstructural, thermal and superconducting properties. The added materials enhance the superconducting properties. We find that even low Pb additions show a dramatic improvement in superconducting properties, with an increase in both T c and J c values of up to 6.35 K and 1.47 × 104 A m−2, respectively. This shows that much lower Pb content superconducting solders can be effective and could be used to replace the PbBi solder commonly used with the superconducting properties T c =8.4 K, H C2 = 1.77 T, H C = 0.0909 T.