Ternary Superconducting Alloys of the Titanium-Niobium-Vanadium System. Transition Temperature Variation

Abstract

The superconducting transition temperature (Tc) variation in the bcc region of the titanium-niobium-vanadium ternary system was studied. Cold-rolled alloys at 10% composition intervals were employed. The Tc values were found to vary smoothly with composition. The highest value in the ternary system was Tc=8.8°K for Ti0.6Nb0.3V0.1. The largest decrease in superconducting properties, relative to the Ti binaries, occurred at the first 10% addition of the third element. Additions of Nb to the Ti–V system and of V to the Ti–Nb system led to more sharply defined peaks in the Tc versus n relationship (n stands for the average number of valence electrons per atom) than found in the binaries. The Tc maximum occurred at n=4.5 for the ternaries with constant vanadium concentration and between n=4.4 and 4.5 for constant niobium concentration. The minimum of Tc in the Nb–V system was found to shift towards higher Nb concentrations with increasing content of Ti. The Tc values were taken to reflect the density of states at the Fermi surface N(0) and their variation was found to be consistent with the rigid d-band model.