The migration of H atoms in quenched Pd-H alloys was investigated, using electrical resistivity measurements at about 50K, in specimens with various H concentrations. The disordered H atoms were introduced by quenching from 100K into liquid He. The disordered H atoms ordered via migration during annealing at 50K. The resistivity increase which was due to H ordering depended largely upon the H concentration, but its magnitude was not proportional to the concentration. The activation energy for H migration was deduced from an analysis of the resistivity increases due to ordering. The obtained value was almost the same for H concentrations ranging from PdH0.06 to PdH0.66, although the tendency was to increase with concentration (figure 21). The energy here was smaller than that at high temperatures, and this was attributed to a tunnelling effect upon diffusion.

Hydrogen Migration in Pd-H Alloys around 50K Anomaly at Various Hydrogen Concentrations. K.Yamakawa: Journal of Physics - Condensed Matter, 1999, 11[44], 8681-8

Figure 21

Diffusivity of H in PdHx