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 96). 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 96

Parameters for H Diffusion in NbHx

 

x

Do (cm2/s)

E (eV)

0.10

3.2 x 10-4

0.115

0.33

4.9 x 10-4

0.142

0.55

1.0 x 10-3

0.168

0.70

7.2 x 10-4

0.174

0.89

5.6 x 10-4

0.164