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Effects of Partial Halide Anion Substitution on Reorientational Motion in NaBH4: A Nuclear Magnetic Resonance Study



R. V. Skoryunov, O. A. Babanova, A. V. Soloninin, A. V. Skripov, Kristina Verdal, Terrence J. Udovic


To study the effects of partial halide anion substitution on the reorientational motion of [BH4] anions in NaBH4, we have measured the 1H and 11B NMR spectra and spin-lattice relaxation rates in the cubic solid solutions Na(BH4)0.5Cl0.5 and Na(BH4)d0.5^I0.5 over broad ranges of temperature (8 K to 324 K) and the resonance frequency (14 MHz to 90 MHz). For both solid solutions, the measured 1H spin-lattice relaxation rates are governed by reorientations of BH4 groups, and the experimental data can be satisfactorily described by the model with a Gaussian distribution of the activation energies. The average values of the activation energies derived from the 1H spin-lattice relaxation data are 192(7) meV for Na(BH4)0.5Cl0.5 and 120(3) meV for Na(BH4)0.5I0.5. At a given temperature, the reorientational jump rates are found to increase in the order Na(BH4)0.5 Cl0.5 - NaBH4 - Na(BH4)0.5I0.5, in agreement with the quasielastic neutron scattering (QENS) results. This trend correlates with the lattice expansion reflecting the increase in the size of the corresponding anions (in the order of Cl - [BH^d4] - I).
Journal of Alloys and Compounds


borohydride, disorder, NMR, nuclear magnetic resonance, reorientational dynamics, sodium borohydride, substitutional disorder


, R. , , O. , , A. , , A. , , K. and Udovic, T. (2015), Effects of Partial Halide Anion Substitution on Reorientational Motion in NaBH<sub>4</sub>: A Nuclear Magnetic Resonance Study, Journal of Alloys and Compounds, [online], (Accessed May 7, 2021)
Created March 4, 2015, Updated February 19, 2017