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 α-Fe and ErH2 occurred exothermally with increasing temperature above 2.0 MPa H2 in the same way as the other RFe2. HIA and precipitation of ErH2 occurred simultaneously in 1.0 MPa H2. On the contrary, hydrogen absorbed crystalline (c-) ErFe2H3.6 decomposed directly into α-Fe+ErH2 below 0.5 MPa H2 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.