Study of CeNi₂ Transformation Upon Hydrogen Absorption

Abstract

RNi₂ Laves phases (R = La, Ce) absorb easily hydrogen up to 4.4 H/mole at room temperature and atmospheric pressure. But X ray diffraction patterns show no diffraction lines. Such a result has already been mentioned by several authors (1–6) for ternary rare-earth and transition metal hydrides. The absence of diffraction lines can be interpreted by the formation of an amorphous compound or by segregation into microcrystalline particles of RH_x and Ni or RNiy (y > 2) (7). The first case would be very interesting since it would provide a new way to prepare amorphous compounds. But until now few studies have been presented on these non crystalline hydrides, except by SAMWER et al (8, 9). These authors have shown that Zr₃Rh become amorphous by hydriding the intermetallic compound at 180 C and atmospheric pressure. They have found the same structural and physical properties for the hydrides prepared from amorphous and crystalline Zr₃Rh.