An electrical resistance analysis of the erbium-hydrogen system

The electrical resistance isotherms have been measured during the interaction of hydrogen at T <= 295 K with films of erbium evaporated in UHV (<= 10-9 Torr). It is shown that the typical points where the isotherm changes its slope correspond to the phase boundaries of the Er-H2 system, and that this agrees with present day ideas on the role of interstitial hydrogen in the various phases. These phase boundaries have previously been determined only for T >= 473 K. The use of the evaporated film as samples has now allowed the boundaries to be found down to 295 K, and the α/(α + β) boundary down to 130 K. Previous experiments which used bulk samples cleaned in a conventional way substantially underestimated the room-temperature solubility limit of hydrogen in the metal. (author)