The effects of yttrium or gadolinium on the superconducting transition temperature of niobium

Abstract

It was found that on quickly cooling from the liquid state during casting, enough Y or Gd was trapped in solid solution in niobium to change the physical properties of the niobium. In particular, the superconducting transition temperature, T c , of Nb was sensitive to small amounts of Y or Gd in solid solution. Yttrium in solid solution raised the T c of Nb, whilst Gd lowered it. On annealing the cast specimens at temperatures up to 1500°C, the Y or Gd precipitates out of solution and the physical properties of niobium revert to those of pure niobium. In addition to the transition temperature ( T c ), the superconducting critical field, ( H c 2 ), the normal state electrical resistivity (ρ), the X-ray lattice parameter ( α o ), and optical and electron microscopy, were used to study the Nb-Y and Nb-Gd alloys.