DIFFERENTIAL THERMAL-ANALYSIS OF HYDROGEN-INDUCED AMORPHIZATION IN C15 LAVES COMPOUNDS GDFE2, GDCO2, GDNI2 (M=FE, CO, NI)

Structural changes of the C15 Laves compounds GdM2 (M = Fe, Co, Ni) during differential thermal analysis (DTA) in a hydrogen atmosphere (0.1-5.0 MPa H2) have been investigated to determine the nature of the hydrogen-induced amorphization (HIA) phenomenon by X-ray diffraction. The DTA curves of GdFe2 exhibit four exothermic peaks resulting from hydrogen absorption, HIA, the precipitation of GdH2 and crystallization for every hydrogen pressure. The DTA curves of GdCo2 and GdNi2 (between 1.0 and 2.0 MPa H2) show three exothermic peaks resulting from hydrogen absorption, HIA and crystallization. On the other hand, the DTA curves of GdNi2 show only two exothermic peaks resulting from amorphization and crystallization below 0.5 MPa H2 and above 5.0 MPa H2.