Comparison of Anion and Cation Dynamics in a Carbon-Substituted closo-Hydroborate Salt: 1H and 23Na NMR Studies of Solid-Solution Na2(CB9H10)(CB11H12)

Published

September 5, 2019

Author(s)

A. V. Soloninin, R. V. Skoryunov, O. A. Babanova, A. V. Skripov, Mirjana NMN Dimitrievska, Terrence J. Udovic

Abstract

The hexagonal mixed-anion solid solution Na₂(CB₉H₁₀)(CB₁₁H₁₂) shows the highest room-temperature ionic conductivity among all known Na-ion conductors. To study the dynamical properties of this compound, we have measured ghe ¹H and ²³Na nuclear magnetic resonance (NMR) spectra and spin-lattice relaxation rates in Na₂(CB₉H₁₀)(CB₁₁H₁₂) over the temperature range of 80 K to 435 K. It is found that the diffusive motion of Na⁺ ions can be described in terms of two jump processes: the fast localized motion within the pairs of tetrahedral interstitial sites of the hexagonal close-packed lattice formed by large anions and the slower jump process via octahedral sites leading to long-range diffusion. Below 350 K, the slower Na⁺ jump process is characterized by the activation energy of 353(11) meV. Although Na⁺ mobility in Na₂(CB₉H₁₀)(CB₁₁H₁₂) found from our NMR experiments is higher than in other ionic conductors, it appears to be an order-of-magnitude lower than that expected on the basis of the conductivity measurements. This result suggests that the complex diffusion mechanism and/or correlations between Na⁺ jumps should be taken into account. The measured ¹H spin-lattice relaxation rates for Na₂(CB₉H₁₀)(CB₁₁H₁₂) are consistent with a coexistence of at least two anion reorientational jump processes occurring at different frequency scales. Near room temperature, both reorientational processes are found to be faster than the Na⁺ jump process responsible for the long-range diffusion.

Citation

Journal of Alloys and Compounds

Volume

800

Pub Type

Journals

Download Paper

Local Download

Keywords

closo-carbaborate, diffusion, ionic conductor, NMR, nuclear magnetic resonance, sodium, sodium ion conductor, solid-state conductor, superionic conductor

Citation

Soloninin, A. , Skoryunov, R. , Babanova, O. , Skripov, A. , Dimitrievska, M. and Udovic, T. (2019), Comparison of Anion and Cation Dynamics in a Carbon-Substituted closo-Hydroborate Salt: ₁H and ²³Na NMR Studies of Solid-Solution Na₂(CB₉H₁₀)(CB₁₁H₁₂), Journal of Alloys and Compounds, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=927728 (Accessed April 25, 2024)