HYDROGEN-INDUCED STRUCTURAL-CHANGES OF FE2CE ALLOYS

The amorphization kinetics of the Fe2Ce Laves phase were studied, util izing X-ray diffraction (XRD), differential scanning calorimetry (DSC) and thermal H desorption measurements. Additionally, the local 1-1 di ffusion process in this ferromagnetic compound was investigated by mea ns of magnetic susceptibility and magnetic after-effect (MAE) measurem ents. Fe2Ce can easily be amorphized (p(H2) = 5 x 10(3) to 1 x 10(5) P a, T < 400 K); irreversible hydrogen-induced amorphization takes place in a narrow phase boundary which migrates from the surface into the s ample. Furthermore, cyclic H-charging of amorphous Fe2Ce below its cry stallization temperature reveals a severe degradation in H-storage cap acity from 53 at.% to 18 at.% after only three cycles. This degradatio n is attributed to a hydrogen-induced phase separation into crystallin e CeH2 and alpha-Fe which is enhanced by the high mobility of Fe atoms .