Comparison of Anion Reorientational Dynamics in MCB 9 H 10 and M 2 B 10 H 10 (M = Li, Na) via Nuclear Magnetic Resonance and Quasielastic Neutron Scattering Studies
[2];
[1];
- Russian Academy of Sciences (RAS), Ekaterinburg (Russian Federation). Inst. of Metal Physics
- National Inst. of Standards and Technology (NIST), Gaithersburg, MD (United States). Center for Neutron Research; National Renewable Energy Lab. (NREL), Golden, CO (United States)
- National Inst. of Standards and Technology (NIST), Gaithersburg, MD (United States). Center for Neutron Research; Univ. of Maryland, College Park, MD (United States). Dept. of Materials Science and Engineering
- Sandia National Lab. (SNL-CA), Livermore, CA (United States)
- Tohoku Univ., Sendai (Japan). Inst. for Materials Research; Tohoku Univ., Sendai (Japan). WPI-Advanced Inst. for Materials Research
- National Inst. of Standards and Technology (NIST), Gaithersburg, MD (United States). Center for Neutron Research
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.
- Research Organization:
- National Renewable Energy Lab. (NREL), Golden, CO (United States)
- Sponsoring Organization:
- USDOE Office of Energy Efficiency and Renewable Energy (EERE), Sustainable Transportation Office. Hydrogen Fuel Cell Technologies Office; USDOE National Nuclear Security Administration (NNSA); National Science Foundation (NSF); Russian Foundation for Basic Research; Japan Society for the Promotion of Science (JSPS)
- Grant/Contract Number:
- AC36-08GO28308; AC04-94AL85000; DMR-0944772; 15-9-2-9; DMR-1508249; 2682031; 25220911
- OSTI ID:
- 1345720
- Report Number(s):
- NREL/JA-5900-68058
- Journal Information:
- Journal of Physical Chemistry. C, Vol. 121, Issue 2; ISSN 1932-7447
- Publisher:
- American Chemical SocietyCopyright Statement
- Country of Publication:
- United States
- Language:
- English
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