Enhancement of the critical current density and upper critical field in Zr and Mo co-doped Nb3Sn

摘要

We prepared a series of Nb3-2xZrxMoxSn (0 <= x <= 0.2) samples which have the same number of electrons per cell as Nb3Sn in order to study the doping effect. The formation of the single phase samples was confirmed by x-ray diffraction when x <= 0.1. It was found that the lattice parameters a decrease slightly with the increasing dopant concentration. The grain morphologies of the sample are irregular. As the dopant content increases, the size of the coarse grain decreases and the content of the fine grain increases. The T-c value of the Nb3-2xZrxMoxSn samples drops slowly when x < 0.1, whereas a sharp decline of T-c occurs when x > 0.1. The T-c drop in the co-doped samples is slower than that in the single-doped ones with the same total dopant concentrations, indicating that the N(E-F) plays an important role in the change of T-c. At 4 T and 10 K, the J(c) value of Nb2.8Zr0.1Mo0.1Sn sample reached 3.4 x 10(6) A cm(-2), which is significantly enhanced by more than 400 and 23 times that of the pure Nb3Sn and single-doped Nb2.8Mo0.2Sn samples, respectively. The H-c2(0) values of the co-doped sample are higher than the pure and single-doped sample. The H-c2(0) value of the Nb2.8Zr0.1Mo0.1Sn sample reached 30 T.