Hydrogen at low temperatures in ordered Fe₃Al alloys

Abstract

The relaxation behaviour of hydrogen and deuterium was studied in ordered (DO₃) Fe₃Al alloys by means of magnetic after-effect measurements. Two relaxation maxima were observed at 55 and 140 K, which are somewhat broader than simple Debye processes. The mean activation energies determined were 0.13 and 0.35eV, respectively. The relaxation processes were attributed to jumps of hydrogen isotopes between two energetically different, octahedral interstitial configurations in the DO₃ lattice. From electronic considerations it is concluded that the interstitial site with Al as nearest-neighbour atom is energetically favoured compared with the configuration possessing only Fe as nearest-neighbour atoms.