抄録
Amorphous superconducting alloys with excellent strength and ductility have been found in rapidly quenched alloys of Nb–Si, Nb–V–Si, Nb–Zr–Si, Nb–Mo–Si, Nb–Ta–Si, Nb–W–Si, Nb–Si–C, Nb–Si–B and Nb–Si–Ge systems. Their continuous ribbons were produced in the form of 1∼1.5 mm width and 0.02∼0.03 mm thickness by using a modified single roller quenching apparatus. The silicon content in these amorphous alloys was limited to a narrow range between about 17 and 21 at%, and the alloy compositions were in the ranges of 0∼20 at% V, 0∼25 at% Zr, 0∼30 at% Mo, 0∼10 at% W, 0∼8 at% C, 0∼12 at% B and 0∼4 at% Ge, respectively. Most of these alloys showed a sharp superconducting transition at a temperature above liquid helium temperature. The transition temperature Tc was in the range of 4.3∼4.4 K for Nb79∼83Si17∼21 alloys. This value increased to 6.7 K after crystallization upon annealing. The addition of Mo, C, B and Ge to the Nb80Si20 alloy brought about a slight increase of Tc and the maximum value was about 5.5 K for Nb50Mo30Si20. The upper critical magnetic field Hc2 and the critical current density Jc were of the order of 2×106 A/m in liquid helium and of 1×104 A/cm2 in liquid helium at zero field.
