Hydride formation in Ce(La)-Ni-Si ternary compounds

Hydrogen interaction with R2Ni0.8Si1.2, R2NiSi, R2Ni1.2Si0.8 and R6Ni2Si3 ( R=La, Ce) compounds were studied. The new hydride phases, namely, La2Ni0.8S i1.2H3.75, La2NiSiH3.9, La2Ni1.2Si0.8H4.4, Ce2Ni0.8Si1.2H3.7, Ce2NiSiH4.4, Ce2Ni1.2Si0.8H4.9, La6Ni2Si3H12 and Ce6Ni2Si3H10.9 have been synthesised an d characterised by X-ray diffraction and thermodesorption methods. All hydr ides retained the structure type of the starting compounds with pronounced anisotropic distortion of crystal lattice: the increase of the <<a>>, param eter at decreasing <<c>>. Variation of the Ni/Si ratio in R2Ni1-xSi1+x (x=0 , 0.4 and -0.4) markedly affected the hydrogen capacity and crystal lattice extension. The Ce-containing hydrides possessed a higher hydrogen contents but significantly smaller specific unit cell volume expansion per one hydr ogen atom in comparison with La-based compounds. (C) 1999 Elsevier Science S.A. All rights reserved.