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© 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/). Notwithstanding the ProQuest Terms and Conditions, you may use this content in accordance with the terms of the License.

Abstract

This study explains the ionic conductivity in the mineral sugilite (idealized formula: Fe2Na2K[Li3Si12O30]) by resolving the dynamic disorder of both Li and Na cations using synchrotron X-ray single-crystal diffraction from 298 K to 1023 K. Non-zero anharmonic atomic displacement parameters at Na and Li sites at 1023 K adumbrated long-range charge transport routes for Li and Na cations commonly parallel to the (ab) plane. Temperature-enhanced diffuse residuals in Fourier maps could unambiguously localize two interstitial sites suitable for Li, as well as three for Na. Each two-dimensional (2D) network of Li and Na interstitials was formed parallel to each other, providing Li and Na hopping pathways. The higher concentration of Na cations hopping in short distances of 2.0962(4)–2.3015(5) Å could be the main reason for the higher bulk conductivity values evaluated by impedance spectra of sugilite in comparison to those of its structural relatives with low Na contents, e.g., the mineral sogdianite ((Zr,Al,Fe)2Na0.36K[Li3Si12O30]). Bond valence sum landscape maps supported the critical role of dynamic disorder of Na+ over densely packed 2D interstitial networks for combined ionic conductivity along with mobile Li+ in sugilite-type compounds.

Details

Title
Mechanism for the Combined Li–Na Ionic Conductivity in Sugilite (Fe2Na2K[Li3Si12O30])-Type Compounds
Author
So-Hyun, Park 1 ; Paulmann, Carsten 2 ; Hoelzel, Markus 3 ; Hochleitner, Rupert 4 

 Department of Geo- and Environmental Sciences, Section of Crystallography, Ludwig-Maximilians-Universität München (LMU), Theresienstr. 41C, 80333 Munich, Germany 
 Department of Earth System Sciences, Institute of Mineralogy and Petrography, University of Hamburg, Grindelallee 48, 20146 Hamburg, Germany; [email protected] 
 Heinz Maier-Leibnitz Zentrum (MLZ), Technische Universität München, Lichtenbergstr. 1, 85748 Garching, Germany; [email protected] 
 Mineralogische Staatssammlung München (SNSB), Theresienstr. 41C, 80333 Munich, Germany; [email protected] 
First page
620
Publication year
2023
Publication date
2023
Publisher
MDPI AG
e-ISSN
2075163X
Source type
Scholarly Journal
Language of publication
English
ProQuest document ID
2819477070
Copyright
© 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/). Notwithstanding the ProQuest Terms and Conditions, you may use this content in accordance with the terms of the License.