Superconductivity of the Composite Consisting of Nb₃Sn Particles Dispersed in Silver

Effect of the Size of Nb₂Sn Particle

Abstract

Superconducting transition temperature (Tc) and critical current density (Jc) of the composite in which Nb₃Sn particles with the average size of 0.07-62μm were dispersed in silver were measured. Tc increased as the increase of the volume fraction of Nb₃Sn (VNb₃Sn) and the diameter of Nb₃Sn particle (dNb₃sn). Jc increased as the increase of VNb₃Sn⋅Jc showed a maximum at around dNb₃Sn=0.10μm. The effect of dNb₃Sn on Tc and Jc could be explained by the superconducting proximity effect. Tc and Jc of Nb₃Sn-Ag composite increased by heat treatment above 962°C (m.p. of Ag) due to the improvement of contact between Nb₃Sn particles and Ag matrix, but decreased by the heat treatment at 1100°C and 1200°C in the case of dNb₃Sn=0.12μm, and at 1400°C in the case of dNb₃Sn=1.0μm owing to the elution of SO from Nb₃Sn into Ag matrix.