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Order-Disorder Transitions and Superionic Conductivity in the Sodium Nido-Undeca(carba)borates

Published

Author(s)

Wan Si NMN Tang, Mirjana NMN Dimitrievska, Vitalie Stavila, Wei Zhou, Hui Wu, A. Alec Talin, Terrence J. Udovic

Abstract

The salt compounds NaB11H14, Na-7-CB10H13, Li-7-CB10H13, Na-7,8-Cd2^B9H12, and Na-7,9-C2B9H12 all contain geometrically similar, monocharged, nido-undeca(carba)borate anions (i.e., truncated icosohedral-shaped clusters constructed of only eleven instead of twelve {B-H} + {C-H} vertices and an additional number of compensating bridging and/or terminal H atoms). We have used first-principles calculations, x-ray powder diffraction, differential scanning calorimetry, neutron vibrational spectroscopy, neutron elastic-scattering fixed-window scans, quasielastic neutron scattering, and electrochemical impedance measurements to investigate their structures, bonding potentials, phase-transition behaviors, anion orientational mobilities, and ionic conductivities compared to those of their closo-poly(carb)borate cousins. All exhibited order-disorder phase transitions somewhere between room temperature and 375 K. All disordered phases appear to possess highly reorientationally mobile anions (>~1010 jumps s-1 above 300 K) and cation-vacancy-rich, close-packed or body-center-cubic-packed structures [like previously investigated closopoly(carba)borates]. Moreover, all disordered phases display superionic conductivities, but with generally somewhat lower values compared to those for the related sodium and lithium salts with similar monocharged 1-CB9H10 and CB11H12 close-carbaborate anions. This study significantly expands the known toolkit of solid-state, poly(carba)borate-based salts capable of superionic conductivities and provides valuable insights into the effect of crystal lattice, unit cell volume, number of carbon atoms incorporated into the anion, and change polarization on ionic conductivity.
Citation
Chemistry of Materials
Volume
29
Issue
24

Keywords

fixed-window scans, ionic conductivity, neutron vibrational spectroscopy, nido-polyborates, polyborates, polycarbaborates, quasielastic neutron scattering, sodium conductors, structural disorder

Citation

NMN, W. , , M. , Stavila, V. , Zhou, W. , Wu, H. , , A. and , T. (2017), Order-Disorder Transitions and Superionic Conductivity in the Sodium Nido-Undeca(carba)borates, Chemistry of Materials, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=924635 (Accessed May 7, 2021)
Created December 26, 2017, Updated February 26, 2019