Effect of independent alloying of zirconium with bronze and niobium on superconducting properties of Nb3Sn in a Cu(Sn)/Nb system

Abstract

The present work focuses on the effect of internal (niobium) and external (bronze) alloying of Zr on the superconducting properties of Nb₃Sn in a Cu(Sn)/Nb system through the diffusion couple method. Alloying of Zr with either Cu(5.5 at.% Sn) or Nb enhances the critical current density (J_c) of the Nb₃Sn superconductor phase developed at the interdiffusion zone of Cu(5.5 at.% Sn, 2 at.% Zr)/Nb and Cu(5.5 at.% Sn)/Nb(2 at.% Zr). Enhancement of J_c of Zr-alloyed Nb₃Sn has been attributed to an increment in grain boundary fraction for Nb₃Sn. Dew Hughes model provided an insight into the pinning mechanisms responsible for enhancement of J_c. Strengthening of pinning forces of Nb₃Sn with internal alloying of Zr might have originated because of the nanometer-sized β-(Nb, Zr) second-phase developed within the Nb₃Sn phase matrix. No change in critical temperature for Zr-alloyed Nb₃Sn makes Zr a suitable alloying element for applications.