Hydrogen-induced amorphization in the C14 laves compound NdMn2

Structural changes in the C14 Laves compound NdMn2 during heating in a hydrogen atmosphere have been investigated by X-ray diffractometry, high-resolution transmission microscopy, differential scanning calorimetry and hydrogen analysis. Hydrogen absorption in the crystalline state, followed by hydrogen-induced amorphization (HIA), precipitation of NdH2 in the amorphous phase and decomposition of the remaining amorphous phase into NdH2 and alpha-Mn, occur sequentially with increasing temperature in H-2 at 5.0 MPa. This represents the first observation of HIA in a C14 Laves compound. As for the C15 Laves compounds, the atomic size ratio appears to be a controlling factor for the occurrence of HIA in C14 Laves compounds.