Hydrogenation studies on NdScSi and NdScGe

Sophie Tencé (1) , Tadgh Mahon (1) , Etienne Gaudin (1) , Bernard Chevalier (1) , Jean-Louis Bobet (1) , Roxana Flacau (1) , Birgit Heying (2) , Ute Ch. Rodewald (2) , Rainer Pöttgen (2)

1 ICMCB - Institut de Chimie de la Matière Condensée de Bordeaux
2 Institut für Anorganische und Analytische Chemie

NdScSi and NdScGe were synthesized from the elements via arc-melting and subsequent annealing. Their ordered La2Sb 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 F2 values for NdScSi and a=431.2(1) and c=1581.3(5) pm, wR2=0.1220, 227 F2 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 H2 pressure shows that the hydride NdScSiH1.48(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 NdScSiD1.5 for the deuteride adopting then the La2Fe2Se2O3-type structure. From magnetization measurements, we evidence that hydrogenation strongly reduces the Curie temperature of NdScSi (TC=175 K) and NdScGe (TC=194 K) since NdScSiH1.5 and NdScGeHx undergo a magnetic transition at 4 K and around 2 K, respectively.

Mots clés: Silicides; Germanides; Crystal chemistry; Hydrogenation reactions; Neutron diffraction; Magnetic properties

Domaines: Matériaux

Sophie Tencé, Tadgh Mahon, Etienne Gaudin, Bernard Chevalier, Jean-Louis Bobet, et al.. Hydrogenation studies on NdScSi and NdScGe. Journal of Solid State Chemistry, 2016, 242 (2), pp.168-174. ⟨10.1016/j.jssc.2016.02.017⟩. ⟨hal-01362245⟩