SUPERCONDUCTING TRANSITION TEMPERATURES OF ZIRCONIUM-NIOBIUM ALLOYS

Measurements of the superconducting transition temperature, Tc, upper critical field and normal state resistivity, have been carried out on a wide range of Zr-Nb alloys heat treated at 585 °C. An extremely rapid rise in transition temperature, from 0.7 °K to 3.5 °K, has been observed in the α-Zr solid solution region (0%-1.25% Nb) which lends support to a recent theoretical model for the density of states of Zr9. The transition temperature continues to increase in the early part of the two-phase region, reaching a value of 10 °K at 6% Nb. The precise value of Tc, in fact, depends on the distribution of the β-precipitate for compositions between 1.25% and 6% Nb. Thereafter tc remains approximately constant with composition up to the β-solid-solubility boundary at 88% Nb. The upper critical field and the normal state resistivity show maxima at 75% Nb, which are discussed in terms of the microstructure. © 1968.