Hydrogen diffusion in NbxTa1−x alloys (x = 0, 0.1, 0.25, 0.5, 0.75, 0.9 and 1.0) was investigated (table 9) between 160 and 340K by measurement of the Gorsky effect. The temperature dependence of the H diffusivity of specimens with x = 0, 0.9 and 1.0 exhibited a deviation from Arrhenius-type behavior at low temperatures, while the other alloys did not exhibit any deviation. The diffusivity decreased with alloying at both the Nb- and Ta-rich ends, and went through a minimum at about x = 0.50. The concentration dependence of the diffusivity was stronger at the Nb-rich end than that at the Ta-rich end. The H potential obtained, using a first-principles calculation showed that a Ta atom acted as a trapping center for H in the Nb matrix and a Nb atom acted as an anti-trapping center in the Ta matrix. It was concluded that the main reason for the decrease in diffusivity was different for the Nb-rich and Ta-rich alloys: H-trapping for the first and a disturbance of tunneling jumps for the second.

Study of Hydrogen Diffusion in Nb–Ta Alloys by Gorsky Effect Measurement. T.Mugishima, M.Yamada, O.Yoshinari: Materials Science and Engineering A, 2006, 442[1-2], 119-23