High-pressure synthesis of novel hydride in Mg–M systems (M = Li, Pd)

Abstract

Phases present and thermal stability of synthesized new compounds in the Mg–Li–H and Mg–Pd systems by preparing under a high pressure were studied. In the Mg–Li–H system, a new hydride with a tentative composition Mg 2LiH 5 is synthesized by exposing a mixture of MgH 2 and LiH to pressures of 2–5 GPa at 973 K for 4 h. The hydride has a cubic structure with the lattice parameter of 0.4219 nm. In the Mg–Pd system, a new intermetallic compound Mg–20 at.% Pd was synthesized at 1073 K and a pressure exceeding 2 GPa. This phase had a bcc structure with a = 1.4053 ( 1 ) nm and it transformed into a low-symmetry phase on heating above 663 K. Moreover, hydrogenation of the compound at 650 K for 3 days under hydrogen pressure of 9 MPa, changed into MgH 2 and new hydride Mg 2PdH x with fcc structure similar to that of Mg 2PdC x [D. Noréus, B. Bogdanović, U. Wilczok, J. Less-Common Met. 169 (1991) 369–373]. The new hydride dehydrogenated at 586 K that is about 100 K lower than MgH 2.