Investigation of the crystallographic structures of LaNi4CoD4.4 and LaNi3.55Mn0.4Al0.3Co0.75Dx (x=2.0 and 4.6 D/f.u.) by neutron powder diffraction

摘要

The structural properties of the deuterides LaNi3.55Mn0.4Al0.3Co0.75Dx with x=2 and 4.6 D/f.u. and LaNi4CoD4.4 have been investigated by means of powder neutron diffraction. The mono-substituted cobalt compound exhibits anisotropic line broadening and crystallises in a different structure than that observed for the fully charged deuteride LaNi4CoD6.1. Such effects are not observed for the deuterides of the three-substituted compound LaNi3.55Mn0.4Al0.3Co0.75 which can be described in the P6/mmm space group. Analysis of the diffraction patterns at different deuterium compositions shows that the plateau pressure extends from 0.6 to 3.4 D/f.u. Beyond this concentration, a large domain of solid solution exists with a progressive filling of the deuterium sites with increasing deuterium pressure. (C) 1998 Elsevier Science S.A. [References: 21]