Method for measuring deuterium in erbium deuteride films

Determining the quantity of deuterium in an erbium deuteride film is essent ial for assessing the quality of the hydriding process but is a challenging measurement to make. First, the ideal gas law cannot be applied directly d ue to high temperature (950 degrees C) and low temperature (25 degrees C) r egions in the same manifold. Additionally, the metal hydride does not relea se all of the deuterium rapidly upon heating and metal evaporation occurs d uring extended heating periods. Therefore, the method developed must provid e a means to compensate for temperature inhomogeneities and the amount of d euterium retained in the metal film while heating Mr a minimal duration. Th is article presents two thermal desorption methods used to evaluate the kin etics and equilibria of the deuterium desorption process at high temperatur es (950 degrees C). Of primary concern is the evaluation of the quantity of deuterium remaining in these films at the high temperature. A multiple vol ume expansion technique provided insight into the kinetics of the deuterium evolution and metal evaporation from the film. Finally, a repeated pump-do wn approach yielded data that indicated approximately 10% of the deuterium is retained in the metal film at 950 degrees C and approximately 1 Torr pre ssure. When the total moles of deuterium determined by this method were div ided by the moles of erbium determined by inductively coupled argon plasma atomic emission spectroscopy, nearly stochiometric values of 2:1 were obtai ned for several erbium dideuteride films. Although this work presents data for erbium and deuterium, these methods are applicable to other metal hydri des as well. (C) 1999 American Vacuum Society. [S0734-2101 (99)03604-0].