Structure and Sodium Ion Dynamics in Sodium Strontium Silicate Investigated by Multinuclear Solid-State NMR

Inglis, Kenneth K, Corley, John P, Florian, Pierre, Cabana, Jordi, Bayliss, Ryan D and Blanc, Frederic ORCID: 0000-0001-9171-1454 (2016) Structure and Sodium Ion Dynamics in Sodium Strontium Silicate Investigated by Multinuclear Solid-State NMR CHEMISTRY OF MATERIALS, 28 (11). pp. 3850-3861. ISSN 0897-4756, 1520-5002

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Abstract

The high oxide ion conductivity of the proposed sodium strontium silicate ion conductors Sr<inf>0.55</inf>Na<inf>0.45</inf>SiO<inf>2.775</inf> (>10^-2 S·cm^-1 at 525 °C) and its unusual alkali metal substitution strategy have been extensively questioned in the literature. Here, we present a comprehensive understanding of the structure of this material using a combination of XRD and multinuclear ¹⁷O, ²³Na, and ²⁹Si solid-state NMR spectroscopy data and a detailed investigation of the Na ion dynamics by high temperature ²³Na NMR line shape analysis and relaxation rates measurements. Both ²³Na and ²⁹Si NMR spectra demonstrate the absence of Na doping in strontium silicate SrSiO<inf>3</inf> and the presence of an amorphous phase identified as Na<inf>2</inf>O·2SiO<inf>2</inf> glass as the Na-containing product. Devitrification at 800 °C yields crystallization of the Na<inf>2</inf>O·2SiO<inf>2</inf> glass into the known crystalline α-Na<inf>2</inf>Si<inf>2</inf>O<inf>5</inf> phase which was positively identified by its XRD pattern and the extensive and clear ¹⁷O, ²³Na, and ²⁹Si NMR fingerprints. High temperature ²³Na NMR reveals that the Na ions are mobile in the Na<inf>2</inf>O·2SiO<inf>2</inf> amorphous component below its glass transition temperature (∼450 °C). In contrast, ²³Na NMR data obtained on the crystalline α-Na<inf>2</inf>Si<inf>2</inf>O<inf>5</inf> shows limited Na dynamics below ∼650 °C, and this result explains the large discrepancy in the conductivity observed in the literature which strongly depends on the thermal history of the Sr<inf>0.55</inf>Na<inf>0.45</inf>SiO<inf>2.775</inf> material. These insights demonstrate that the high conductivity observed in Sr<inf>0.55</inf>Na<inf>0.45</inf>SiO<inf>2.775</inf> is due to Na conduction in the Na<inf>2</inf>O·2SiO<inf>2</inf> glass, and this motivates the quest for the discovery of low temperature fast ion conductors in noncrystalline solids.

Item Type:	Article
Uncontrolled Keywords:	34 Chemical Sciences, 3406 Physical Chemistry
Depositing User:	Symplectic Admin
Date Deposited:	01 Jul 2016 15:13
Last Modified:	16 Jun 2026 09:52
DOI:	10.1021/acs.chemmater.6b00941
Related Websites:	Author Publisher
URI:	https://livrepository.liverpool.ac.uk/id/eprint/3001982
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• Structure and Sodium Ion Dynamics in Sodium Strontium Silicate Investigated by Multinuclear Solid-State NMR (deposited 13 Jun 2016 08:55)
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