Electronic and crystallographic properties of the system CeY2Ni9Dx (0≤x≤8.7) measured by X-ray absorption spectroscopy

The electronic and crystallographic properties of CeY2Ni9Dx (0≤x≤8.7D/f.u.) have been investigated by X-ray absorption spectroscopy (XAS). The PuNi3-type structure (space group R3¯m) is described as a stacking of RM2 and RM5 units (R: Y, Ce; M: Ni). Hydrogen occupies the RM2 units only. The Ce-LIII and Ni-K edges have been measured by XAS as a function of hydrogen uptake. A heterogeneous mixed valence state is reported for Ce in the hydride and related to differences in deuterium site occupancies. Huge anisotropic volume expansion is observed and is related to hydrogen absorption and valence change of Ce.