Disorder and Oxide Ion Diffusion Mechanism in La_1.54Sr_0.46Ga₃O_7.27 Melilite from Nuclear Magnetic Resonance

Corti, Lucia, Iuga, Dinu, Claridge, John B ORCID: 0000-0003-4849-6714, Rosseinsky, Matthew J ORCID: 0000-0002-1910-2483 and Blanc, Frederic ORCID: 0000-0001-9171-1454 (2023) Disorder and Oxide Ion Diffusion Mechanism in La_1.54Sr_0.46Ga₃O_7.27 Melilite from Nuclear Magnetic Resonance JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 145 (40). pp. 21817-21831. ISSN 0002-7863, 1520-5126

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Abstract

Layered tetrahedral network melilite is a promising structural family of fast ion conductors that exhibits the flexibility required to accommodate interstitial oxide anions, leading to excellent ionic transport properties at moderate temperatures. Here, we present a combined experimental and computational magic angle spinning (MAS) nuclear magnetic resonance (NMR) approach which aims at elucidating the local configurational disorder and oxide ion diffusion mechanism in a key member of this structural family possessing the La<inf>1.54</inf>Sr<inf>0.46</inf>Ga<inf>3</inf>O<inf>7.27</inf> composition. ¹⁷O and ⁷¹Ga MAS NMR spectra display complex spectral line shapes that could be accurately predicted using a computational ensemble-based approach to model site disorder across multiple cationic and anionic sites, thereby enabling the assignment of bridging/nonbridging oxygens and the identification of distinct gallium coordination environments. The ¹⁷O and ⁷¹Ga MAS NMR spectra of La<inf>1.54</inf>Sr<inf>0.46</inf>Ga<inf>3</inf>O<inf>7.27</inf> display additional features not observed for the parent LaSrGa<inf>3</inf>O<inf>7</inf> phase which are attributed to interstitial oxide ions incorporated upon cation doping and stabilized by the formation of five-coordinate Ga centers conferring framework flexibility. ¹⁷O high-temperature (HT) MAS NMR experiments capture exchange within the bridging oxygens at 130 °C and reveal coalescence of all oxygen signals in La<inf>1.54</inf>Sr<inf>0.46</inf>Ga<inf>3</inf>O<inf>7.27</inf> at approximately 300 °C, indicative of the participation of both interstitial and framework oxide ions in the transport process. These results further supported by the coalescence of the ⁷¹Ga resonances in the ⁷¹Ga HT MAS NMR spectra of La<inf>1.54</inf>Sr<inf>0.46</inf>Ga<inf>3</inf>O<inf>7.27</inf> unequivocally provide evidence of the conduction mechanism in this melilite phase and highlight the potential of MAS NMR spectroscopy to enhance the understanding of ionic motion in solid electrolytes.

Item Type:	Article
Additional Information:	No access restrictions: data can be made immediately available.
Uncontrolled Keywords:	3402 Inorganic Chemistry, 34 Chemical Sciences
Divisions:	Faculty of Science & Engineering > School of Physical Sciences
Depositing User:	Symplectic Admin
Date Deposited:	03 Oct 2023 14:29
Last Modified:	22 May 2026 16:29
DOI:	10.1021/jacs.3c04821
Related Websites:	Author Publisher
URI:	https://livrepository.liverpool.ac.uk/id/eprint/3173359
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