ИСТИНА

Intermetallic compounds (IMC) with composition RT3 (R=Earth Rare Metal, T= Co, Ni, Rd) are perspective material for hydrogen energy due to the ability of storage of hydrogen compactly and safety [1]. Most of RT3 compounds crystallized in PuNi3 (R-3m, SG № 166) and CeNi3 (P63/mmc, SG № 194) structure types. The structure of RT3 compounds consists of the fragments with RT2 composition (MgZn2 structure) and RT5 composition (CaCu5 structure), stacking perpendicularly of the crystallographic z axis. Under hydrogenation, hydrogen atoms fill out different sites in the metal matrix of compounds. The crystallographic positions of the interstitials suitable for hydrogen incorporation form hydrogen sublattices in the metal matrix of hydride [2]. At low temperature occurs redistribution of the hydrogen atoms in the sites of the hydrogen sublattice and takes place formation of different hydride phases. In work [3] was revealed that interaction of hydrogen with CeNi3 and CeCo3 intermetallic compounds leads to formation of the stable hydride phases with medium hydrogen concentration (3-4 atom H per formula unit). These hydrides not desorb hydrogen at atmosphere pressure and room temperature. Increasing pressure of hydrogen leads to the growing of the hydrogen concentration in these and some other hydrides [4]. The stability of these hydrides not changes, and after decreasing of the pressure desorption of the hydrogen from hydrides not occurs (fig. 1) [4].Decreasing of the temperature sometime leads to transition from stability to non-stability of these hydrides and these phases start to desorb the hydrogen. This happens with hydrides having both medium and high concentration of the hydrogen. For several compounds (CeNi3, NdNi3, GdNi3 and ErNi3) interaction with hydrogen at low temperature leads to formation partly amorphous samples of hydrides. This behavior probably occurs due to the redistribution of hydrogen atoms in the sites of the hydrogen sublattices. During decreasing of the temperature in hydrides arises ordering of the hydrogen atoms and take place a formation of several new hydride phases, including hydrides with partly amorphous metal matrix. Similar behavior was described early in literature for hydrides of the d-metals [5]. [1]. M. Latroche, A. Percheron-Guegan (2003). Structural and thermodynamic studies of some RM3-compounds (R=lanthanide, M=transition metal). J. Alloys Compd. 356-357, 461-468. [2] V.A. Yartys (1992). New aspects of the structural chemistry of intermetallic hydrides: «isotropic» and «anisotropic» structures. Koord. Khim. 18, № 4, 401-408. [3] R.H. Van Essen, K.H.J. Buschow (1980). Hydrogen sorption characteristics of Ce-3d and Y-3d intermetallic compounds. J. Less-Common. 70, 189-198. [4] S.А. Lushnikov, S.N. Klyamkin, Т.V. Filippova, A.V. Gribanov (2011). NdRh3-based intermetallic hydrides. Inorganic Materials. 47, №3, 240-243. [5] V.A. Somenkov (1972). Structure of hydrides. Ber. Bunsen-Ges. Phys. Chem. 76, 724–728. [6] S.А. Lushnikov, Т.V. Filippova, I.A. Bobrikov (2017). On the structure stable CeNi3-based hydrides. J. Surf. Investig. 11, №1, 190-193.