Abstract
A superconducting amorphous phase with high strength and good ductility has been found in rapidly quenched alloys of the Zr–Nb–Ge system. The amorphous phase was formed in a wide composition range from 0 to 65 at%Nb and from 11 to 21 at%Ge. All the amorphous alloys showed a superconducting transition whose temperature, Tc, increased from 2.59 to 3.38 K with increasing Nb content and with decreasing Ge content. The upper critical magnetic field and critical current density for a Zr45Nb40Ge15 alloy were of the order of 2.47×106 Am−1 and 2.40×106 Am−2, respectively, at 1.70 K in the absence of applied field. The upper critical field gradient at Tc, −(dHc2⁄dT)Tc, and the electrical resistivity at 4.2 K, ρn, decreased from 2.29×106 to 1.31×106 Am−1 K−1 and 2.70 to 2.00 μΩm, respectively with the amount of Nb. The GL parameter κ and the GL coherence length ξGL(0) were estimated to be 64–101 and about 8.2 nm, respectively, from the experimental values of (dHc2⁄dT)Tc and ρn by using the GLAG theory, and hence it is concluded that the Zr–Nb–Ge amorphous alloys are extremely “dirty” type-II superconductor having very weak flux pinning force.
