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

Published

March 4, 2015

Author(s)

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

Abstract

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)_0.5Cl_0.5 and Na(BH₄₎d0.5^I_0.5 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)_0.5Cl_0.5 and 120(3) meV for Na(BH₄)_0.5I_0.5. At a given temperature, the reorientational jump rates are found to increase in the order Na(BH₄)_0.5 Cl_0.5 - NaBH₄ - Na(BH₄)_0.5I_0.5, 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).

Citation

Journal of Alloys and Compounds

Volume

636

Pub Type

Journals

Download Paper

Local Download

Keywords

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

Citation

Skoryunov, R. , Babanova, O. , Soloninin, A. , Skripov, A. , Verdal, K. and Udovic, T. (2015), Effects of Partial Halide Anion Substitution on Reorientational Motion in NaBH₄: A Nuclear Magnetic Resonance Study, Journal of Alloys and Compounds, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=917906 (Accessed April 23, 2024)