Pressure dependence of hydrogen-induced amorphization in C15 Laves phase ErFe2

C15 Laves phase ErFe2 was thermally analyzed using a pressure differential scanning calorimeter (PDSC) in a hydrogen atmosphere. Hydrogen absorption in a crystalline state, hydrogen-induced amorphization (HIA), precipitation of ErH2 in the amorphous phase and decomposition of the remaining amorphous phase into alpha-Fe and ErH2 occurred exothermally with increasing temperature above 2.0 MPa H-2 in the same way as the other RFe2. HIA and precipitation of ErH2 occurred simultaneously in 1.0 MPa H-2. On the contrary, hydrogen absorbed crystalline (c-) ErFe2H3.6 decomposed directly into alpha-Fe + ErH2 below 0.5 MPa H-2 without formation of an amorphous phase. A reason why HIA is observed above the critical hydrogen pressure is discussed on the basis of the hydrogen content in crystalline c-ErFe2Hx. (C) 2003 Elsevier B.V. All rights reserved.