A comparison of diffusion in microcrystalline and crystalline films was made by using an electrochemical permeation technique. In the case of the microcrystalline film, the transient diffusion curves were found to comprise 2 steps. These were tentatively attributed to a transition from the  phase to a hydride phase, and to subsequent migration of the phase boundary. No such behavior was exhibited by the crystalline material. This was attributed to slower diffusion, as compared with microcrystalline film. The H diffusion coefficients in microcrystalline films clearly increased with increasing H concentration, whereas there was a negligible concentration dependence in the case of the crystalline material.

Z.Zhou, J.Huang, W.Hu, F.Yao, Y.Zhang: Journal of Alloys and Compounds, 1995, 231, 297-301