CeMnA1H x, a new metal hydride

Abstract

In contrast to CeAl 2, which does not form hydrides, and CeMn which does not form binary intermetallic compounds at all, CeMnAl absorbs considerable amounts of hydrogen. A stable hydride phase (β-phase) is formed at low pressures (<10 mbar) with a capacity of about 1.2 H/formula unit (f.u.). Hydrogen is absorbed up to 2.4 H/f.u. at pressures > 10 mbar (at 300 K). In this work we show the absorption characteristics and structural properties of this new metal hydride. The intermetallic compound CeMnAl crystallizes in the cubic C15 Laves phase as observed by X-ray diffraction. Neutron scattering experiments on this intermetallic compound show that the Mn and Al atoms are distributed randomly on the B sites in this AB 2-type C15 Laves phase compound (A = Ce; B = Mn, Al). Upon hydride (deuteride) formation the C15 structure is preserved. The deuterium atoms occupy only the 2A-2B-tetrahedral interstitial sites (96g-positions) over the investigated concentration range 0.0<×≤2.5 in CeMnAID x .