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Title: 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

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.
Authors:
 [1] ; ORCiD logo [2] ; ORCiD logo [1] ;  [1] ;  [1] ;  [3] ;  [4] ;  [5] ;  [6]
  1. Russian Academy of Sciences (RAS), Ekaterinburg (Russian Federation). Inst. of Metal Physics
  2. National Inst. of Standards and Technology (NIST), Gaithersburg, MD (United States). Center for Neutron Research; National Renewable Energy Lab. (NREL), Golden, CO (United States)
  3. 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
  4. Sandia National Lab. (SNL-CA), Livermore, CA (United States)
  5. Tohoku Univ., Sendai (Japan). Inst. for Materials Research; Tohoku Univ., Sendai (Japan). WPI-Advanced Inst. for Materials Research
  6. National Inst. of Standards and Technology (NIST), Gaithersburg, MD (United States). Center for Neutron Research
Publication Date:
Report Number(s):
NREL/JA-5900-68058
Journal ID: ISSN 1932-7447
Grant/Contract Number:
AC36-08GO28308; AC04-94AL85000; DMR-0944772; 15-9-2-9; DMR-1508249; 2682031; 25220911
Type:
Accepted Manuscript
Journal Name:
Journal of Physical Chemistry. C
Additional Journal Information:
Journal Volume: 121; Journal Issue: 2; Journal ID: ISSN 1932-7447
Publisher:
American Chemical Society
Research Org:
National Renewable Energy Lab. (NREL), Golden, CO (United States)
Sponsoring Org:
USDOE Office of Energy Efficiency and Renewable Energy (EERE), Fuel Cell Technologies Office (EE-3F); USDOE National Nuclear Security Administration (NNSA); National Science Foundation (NSF); Russian Foundation for Basic Research; Japan Society for the Promotion of Science (JSPS)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; NMR; quasielastic neutron scattering; anions
OSTI Identifier:
1345720