Yg. Kim et al., AMORPHIZATION OF THE CRYSTALLINE CERU2 HYDRIDE AND THE EFFECTS OF GD SUBSTITUTION ON THE AMORPHIZATION BEHAVIOR, Journal of alloys and compounds, 202, 1993, pp. 203-209
The structural changes of CeRU2 during hydrogen absorption or desorpti
on are examined by X-ray diffraction, differential scanning calorimetr
y and transmission electron microscopy. CeRU2 decomposes into the micr
ocrystalline phases CeH2 and alpha-Ru upon hydrogenation at 400-degree
s-C. The crystalline hydride phase is amorphized by partial desorption
of hydrogen even at room temperature. To examine the amorphization me
chanism, some of the Ce atoms are replaced by Gd atoms within the stab
ility range of the C15 Laves structure. As the fraction of Gd increase
s, the degree of amorphization becomes lower. It is proposed that the
amorphization of (Ce, Gd)Ru2 hydride is closely related to the presenc
e of Ce and H atoms. The large volume change during hydrogen desorptio
n may lead to elastic instability of the compound and the remaining H
atoms stabilize the amorphous structure.