The diffusion of H in group-V transition metals was measured, at temperatures ranging from 500 to 1100C, by using absorption methods. The data which were obtained at high temperatures agreed well with the published results of resistivity and other studies. They did not agree with data which had been obtained at moderate temperatures by using the same absorption method. Below some critical temperature (540 to 700C), the values of the diffusion coefficient deviated downwards from the linear Arrhenius plot (figure 14). This deviation was attributed to the effect of surface layers, such as oxide films, which affected H absorption by the metal.

Diffusion of Hydrogen at High Temperatures in the Group V Transition Metals and Alloying Effect on the Diffusion. T.Eguchi, S.Morozumi: Journal of the Japan Institute of Metals, 1977, 41[8], 795-802

Figure 14

Diffusivity of H in Nb