A pulsed field gradient nuclear magnetic resonance spin-echo technique was used to measure diffusivities. The activation energy increased with increasing H concentration, whereas the pre-exponential factor was not greatly concentration-dependent (table 162). The results were not consistent with the random occupation of tetrahedral sites, and it was suggested that repulsive interactions existed between H atoms on nearest-neighbor sites.

P.E.Mauger, W.D.Williams, R.M.Cotts: Journal of the Physics and Chemistry of Solids, 1981, 42[9], 821-6

 

 

 

Table 162

Parameters for H Diffusion in TaHx

 

x

Do (cm2/s)

E (eV)

0.12

3.1 x 10-4

0.143

0.17

4.6 x 10-4

0.164

0.34

3.5 x 10-4

0.162

0.38

4.1 x 10-4

0.170

0.52

4.3 x 10-4

0.182

0.74

2.6 x 10-4

0.170

0.77

3.3 x 10-4

0.183