Hydrogenation studies on NdScSi and NdScGe
NdScSi and NdScGe were synthesized from the elements via arc-melting and subsequent annealing. Their ordered La{sub 2}Sb type structures, with space group I4/mmm, were refined from single crystal X-ray diffractometer data: a=428.94(6) and b=1570.5(3) pm, wR2=0.0395, 309 F{sup 2} values for NdScSi and a=431.2(1) and c=1581.3(5) pm, wR2=0.1220, 227 F{sup 2} values for NdScGe, with 11 variables per refinement. Hydrogen insertion was performed on both Nd-based intermetallics by solid/gas reaction. Hydrogen uptake keeps the pristine compound space group but yields an anisotropic expansion of the unit cell with a large increase of c (≈+7%) and a slight decrease of a (≈−1.7%) parameters. Hydrogen absorption at 350 °C and under 5 bar of H{sub 2} pressure shows that the hydride NdScSiH{sub 1.48(5)} is formed. An in-situ neutron diffraction study during the deuteration of NdScSi reveals for the first time in a CeScSi-type compound, the possibility to fill two interstitial sites with deuterium atoms, leading to the composition NdScSiD{sub 1.5} for the deuteride adopting then the La{sub 2}Fe{sub 2}Se{sub 2}O{sub 3}-type structure. From magnetization measurements, we evidence that hydrogenation strongly reduces the Curie temperature of NdScSi (T{sub C}=175 K) and NdScGe (T{sub C}=194 K) since NdScSiH{sub 1.5} and NdScGeH{sub x} undergo a magnetic transition at 4 K and around 2 K, respectively. - Highlights: • Crystal structures of NdScSi and NdScGe were refined from single crystal XRD data. • The hydrogenation of NdScSi leads to the formation of the NdScSiH{sub 1.5} hydride. • NdScSiD{sub 1.5} adopts the La{sub 2}Fe{sub 2}Se{sub 2}O{sub 3}-type structure. • Hydrogenation strongly reduces the ordering temperature of both intermetallics.