The reorientational motion of BH4 groups and the translational diffusion of Li+ ions in LiBH4-LiI solid solutions with 2:1, 1:1 and 1:2 molar ratios were studied by measuring the 1H, 11B and 7Li NMR spectra and spin-lattice relaxation rates in these compounds at 18 to 520K. It was found that, at low temperatures, the reorientational motion of the BH4 groups in LiBH4-LiI solid solutions was considerably faster than that in all other borohydride-based systems. The results were consistent with the coexistence of at least two types of reorientational processes having differing characteristic rates. For the faster reorientational process, the average activation energies derived from the data were 53, 39 and 33meV for LiBH4-LiI solid solutions with 2:1, 1:1 and 1:2 molar ratios, respectively. Over the studied range of iodine concentrations, the Li+ jump rates decreased with increasing I- content. The activation energies for Li diffusion, deduced from the data, were 0.63, 0.65 and 0.68eV for samples with 2:1, 1:1 and 1:2 molar ratios, respectively.

Nuclear Magnetic Resonance Studies of Reorientational Motion and Li Diffusion in LiBH4-LiI Solid Solutions. A.V.Skripov, A.V.Soloninin, L.H.Rude, T.R.Jensen, Y.Filinchuk: Journal of Physical Chemistry C, 2012, 116[50], 26177-84

Table 204

Diffusivity of Cu in NaI Single Crystals