TY - JOUR
T1 - Comparison of Anion Reorientational Dynamics in MCB9H10 and M2B10H10 (M = Li, Na) via Nuclear Magnetic Resonance and Quasielastic Neutron Scattering Studies
AU - Soloninin, Alexei V.
AU - Dimitrievska, Mirjana
AU - Skoryunov, Roman V.
AU - Babanova, Olga A.
AU - Skripov, Alexander V.
AU - Tang, Wan Si
AU - Stavila, Vitalie
AU - Orimo, Shin Ichi
AU - Udovic, Terrence J.
N1 - Funding Information:
This work was performed, in part, in collaboration between members of IEA HIA Task 32- Hydrogen-Based Energy Storage, and within the assignment of the Russian Federal Agency of Scientific Organizations (program "Spin" No. 01201463330). The authors gratefully acknowledge support from the Russian Foundation for Basic Research under Grant No. 15-03-01114; the Ural Branch of the Russian Academy of Sciences under Grant No. 15-9-2-9; the Collaborative Research Center on Energy Materials, Tohoku University; and JSPS KAKENHI under Grant Nos. 25220911 and 2682031. A. V. S. gratefully acknowledges travel support from CRDF Global in conjunction with this work under Grant No. FSCX-15-61826-0. M.D. gratefully acknowledges support from the US DOE Office of Energy Efficiency and Renewable Energy, Fuel Cell Technologies Office, under Contract No. DE-AC36- 08GO28308. Sandia National Laboratories is a multiprogram laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the US DOE's National Nuclear Security Administration under Contract No. DE-AC04-94AL85000. This work utilized facilities supported in part by the National Science Foundation under Agreement DMR-0944772 and DMR-1508249. The opinions, findings, and conclusions stated herein are those of the authors and do not necessarily reflect those of CRDF Global. The authors thank J. J. Rush, D. A. Neumann, and C. M. Brown for helpful discussions.
Publisher Copyright:
© 2016 American Chemical Society.
PY - 2017/1/19
Y1 - 2017/1/19
N2 - The disordered phases of the 1-carba-closo-decaborates LiCB9H10 and NaCB9H10 exhibit the best solid-state ionic conductivities to date among all known polycrystalline competitors, likely facilitated in part by the highly orientationally mobile CB9H10- anions. We have undertaken both NMR and quasielastic neutron scattering (QENS) measurements to help characterize the monovalent anion reorientational mobilities and mechanisms associated with these two compounds and to compare their anion reorientational behaviors with those for the divalent B10H102- anions in the related Li2B10H10 and Na2B10H10 compounds. NMR data show that the transition from the low-T ordered to the high-T disordered phase for both LiCB9H10 and NaCB9H10 is accompanied by a nearly two-orders-of-magnitude increase in the reorientational jump rate of CB9H10- anions. QENS measurements of the various disordered compounds indicate anion jump correlation frequencies on the order of 1010-1011 s-1 and confirm that NaCB9H10 displays jump frequencies about 60% to 120% higher than those for LiCB9H10 and Na2B10H10 at comparable temperatures. The Q-dependent quasielastic scattering suggests similar small-angular-jump reorientational mechanisms for the different disordered anions, changing from more uniaxial in character at lower temperatures to more multidimensional at higher temperatures, although still falling short of full three-dimensional rotational diffusion below 500 K within the nanosecond neutron window.
AB - The disordered phases of the 1-carba-closo-decaborates LiCB9H10 and NaCB9H10 exhibit the best solid-state ionic conductivities to date among all known polycrystalline competitors, likely facilitated in part by the highly orientationally mobile CB9H10- anions. We have undertaken both NMR and quasielastic neutron scattering (QENS) measurements to help characterize the monovalent anion reorientational mobilities and mechanisms associated with these two compounds and to compare their anion reorientational behaviors with those for the divalent B10H102- anions in the related Li2B10H10 and Na2B10H10 compounds. NMR data show that the transition from the low-T ordered to the high-T disordered phase for both LiCB9H10 and NaCB9H10 is accompanied by a nearly two-orders-of-magnitude increase in the reorientational jump rate of CB9H10- anions. QENS measurements of the various disordered compounds indicate anion jump correlation frequencies on the order of 1010-1011 s-1 and confirm that NaCB9H10 displays jump frequencies about 60% to 120% higher than those for LiCB9H10 and Na2B10H10 at comparable temperatures. The Q-dependent quasielastic scattering suggests similar small-angular-jump reorientational mechanisms for the different disordered anions, changing from more uniaxial in character at lower temperatures to more multidimensional at higher temperatures, although still falling short of full three-dimensional rotational diffusion below 500 K within the nanosecond neutron window.
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U2 - 10.1021/acs.jpcc.6b09113
DO - 10.1021/acs.jpcc.6b09113
M3 - Article
AN - SCOPUS:85017513680
VL - 121
SP - 1000
EP - 1012
JO - Journal of Physical Chemistry C
JF - Journal of Physical Chemistry C
SN - 1932-7447
IS - 2
ER -