Regensburg 2002 – scientific programme
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M: Metallphysik
M 24: Wasserstoff in Metallen I
M 24.3: Fachvortrag
Thursday, March 14, 2002, 10:00–10:15, H4
NMR Studies of Hydrogen and Deuterium Diffusion in Hafnium Dihydrides/Dideuterides — •Günter Majer1, Jürgen Gottwald1, David T. Peterson2, and Richard G. Barnes2 — 1Max-Planck-Institut für Metallforschung, Heisenbergstraße 1, 70569 Stuttgart — 2Ames Laboratory, Iowa State University, Ames, Iowa 50011, USA
The macroscopic diffusivity D and the spin-lattice relaxation rate Γ1 of hydrogen in hafnium dihydrides, HfHx (1.71 ≤ x ≤ 1.94), have been measured by NMR. The activation enthalpy, obtained by fitting an Arrhenius expression to D(T), increases with increasing x from Ha =0.63 eV (x=1.71) to Ha =0.71 eV (x=1.94). These Ha values agree well with those deduced from the Γ1 data. A comparison of the Γ1 and D measurements shows that the hydrogen atoms jump between adjacent T-sites. The deuterium spin-lattice relaxation rate measured on HfDx (1.68 ≤ x ≤ 1.90) is dominated by the quadrupolar relaxation Γ1,quad. The fluctuations in the electric field gradients are related to the jumps of the vacancies on the deuterium sublattice. The Γ1,quad maximum occurs at a lower temperature than the dipolar maximum, reflecting the higher jump frequency of the vacancies compared to the deuterium atoms.