Enhancement of the critical current density and upper critical field in Zr and Mo co-dopedNb3Sn

Abstract

We prepared a series of Nb3−2xZrxMoxSn (0≤x≤0.2) samples which have the same number of electrons per cell asNb3Sn in order tostudy the doping effect. The formation of the single phase samples was confirmed by x-ray diffraction whenx≤0.1. It was found that thelattice parameters a decrease slightly with the increasing dopant concentration. The grain morphologiesof the sample are irregular. As the dopant content increases, the size ofthe coarse grain decreases and the content of the fine grain increases. TheTc value of theNb3−2xZrxMoxSn samples drops slowlywhen x<0.1, whereas asharp decline of Tc occurs when x>0.1. The Tc drop in the co-doped samples is slower than that in the single-dopedones with the same total dopant concentrations, indicating that theN(EF) plays an importantrole in the change of Tc. At 4 T and 10 K, the Jc value of Nb2.8Zr0.1Mo0.1Sn sample reached 3.4 × 106 A cm−2, which is significantly enhanced by more than 400 and 23 times that of the pureNb3Sn and single-dopedNb2.8Mo0.2Sn samples,respectively. The Hc2(0) values of the co-doped sample are higher than the pure and single-doped sample. TheHc2(0) valueof the Nb2.8Zr0.1Mo0.1Sn sample reached 30 T.