Nuclear Magnetic Resonance Wide-Line Study of Hydrogen in the Yttrium-Yttrium Dihydride System

摘要

The exp 1 H nuclear magnetic resonance was studied in the yttrium-hydrogen system YH/sub x/ in the composition range 0.20 less than or equal to x less than or equal to 1.98 and temperature range 77 K less than or equal to T less than or equal to 490 exp 0 K. Both alpha - and beta -phases of YH/sub x/ were investigated in polycrystalline (powdered) specimens. Rigid lattice proton resonance second moments were obtained for both alpha - and beta -phase samples. Analysis of the second moment for alpha -YH/sub x/ ( alpha -phase) indicates that the hydrogen resides in both the tetrahedral and octahedral interstitial sites of the hcp Y lattice. Second moment values for beta -YH/sub x/ ( beta -phase) indicate that a sizeable fraction of the octahedral interstitial sites in the fcc yttrium metal lattice are occupied by hydrogen, while a nonnegligible fraction of the tetrahedral interstitial sites are vacant. For example, in YH/sub 1.98/, 28% of the octahedral sites are occupied, while 15% of the tetrahedral sites are vacant. The results for beta -YH/sub x/ also indicate that as the H concentration increases, the probability of H occupation of octahedral sites increases. (ERA citation 05:016132)