Demonstration of excellent 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 ratios 0.5-5 wt % have been added into SnIn (35:65) to investigate their microstructural, thermal and superconducting properties. The added materials enhanced the superconducting properties. We find that even low Pb additions showed a dramatic improvement in superconducting properties, with an increase in both Tc and Jc values up to 6.35 K and 1.47×104 A/m2, 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 Tc = 8.4K, HC2 = 1.77 T, HC = 0.0909 T.