Pulsed gradient nuclear magnetic resonance methods were used to measure H diffusion in the ß-phase material, Ni5LaHx, where x ranged from 6 to 7. The results, for temperatures of 331 to 375K, could be described by the Arrhenius relationship:

D (cm2/s) = 0.14 exp[-40(kJ/g-atom)/RT]

as compared with the result for the a-type material,

D (cm2/s) = 0.03 exp[-40(kJ/g-atom)/RT]

It was suggested that the higher diffusivity in the ß-type material was related to a 25% lattice expansion which occurred during the transition.

R.F.Karlicek, I.J.Lowe: Solid State Communications, 1979, 31[3], 163-5