Two-dimensional diffusion of hydrogen inZrBe2H1.4

Abstract

The dift'usion of hydrogen through the hexagonal metal hydride ZrBe&H& 4 has been studied by measuring the H nuclear spin-lattice relaxation rate T~a s a function of frequency and temperature. At high temperatures, where the hopping rate of the H interstitials is faster than the nuclear magnetic resonance (NMR) frequency, the relaxation rate has a frequency dependence much larger than expected for random diffusive motion in three dimensions. A previous NMR study of ZrBe2H& 4 did not account for the anomalous frequency dependence. Our data more fully define the frequency dependence, and we find that it is consistent with a model in which the motion of the hydrogen is restricted to two dimensions. Two-dimensional motion allows a self-consistent analysis of the Td ata for all the measured frequencies and provides an improved measure of the activation energy, E = 0.27 + 0.02 eV. The frequency dependence of T~c an be used to identify two-dimensional motion in a randomly oriented powder sample.

Lithium motion in the anode material LiC6as seen via time-domain7Li NMR

“…In agreement with the results of Eqs. (3) and (4) 29 previously in the 2D H + ion conductor ZrBe 2 H 1.4 (ZBH). In ZBH the deviation is ascribed to long-range H motion in the presence of a magnetic field gradient which is due to the nonzero magnetic susceptibility of the metal hydride.…”

“…Let us first discuss the central line of the spectrum which is also determined by a distinct powder pattern because of electric 094304-2 32,33 At high temperatures the central line reveals a slight anisotropic broadening which reflects the Li ions exposed to the layer structure of LiC 6 . Furthermore, in this high-T range, the NMR linewidths of the two-pulse spectra are presumably affected by internal inhomogeneous magnetic fields 29 that arise from the nonzero susceptibility of the LiC 6 particles (see also below, Sec. III B2).…”

Ion dynamics in solid electrolytes for lithium batteries

“…Worth noting, the frequency dispersion of the high-T flank of the rate peaks indicates spatially confined Li ion diffusion. Indeed, 6 Li NMR spin-lattice relaxation reveals the same characteristics which can be interpreted as 2D ionic motions [70,114,115] in the layered structure of LiBH 4 [116]. As the 6 Li nucleus (spin-quantum number I = 1) is subject to much less dipolar and quadrupolar interactions it can be described as a quasi spin-1/2 nucleus.…”

Li jump process inh−Li0.7TiS2studied by two-timeWilkening1, Heitjans2 2008Phys. Rev. B9881581View full textAdd to dashboardCite

“…30 h-Li x TiS 2 is one of only few examples where the 2D nature of cation diffusion was probed by frequency and temperature dependent measurements, see, e.g., Ref. 35 for an analogous 1 H NMR relaxation study of proton diffusion in polycrystalline ZrBe 2 H 1. 4 .…”