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Improved understanding of atomic ordering in Y4SixAI2-xO9-xNx materials using a combined solid-state NMR and computational approach

Improved understanding of atomic ordering in Y4SixAI2-xO9-xNx materials using a combined solid-state NMR and computational approach
Improved understanding of atomic ordering in Y4SixAI2-xO9-xNx materials using a combined solid-state NMR and computational approach
Ceramics based around silicon aluminum oxynitrides are of both fundamental structural chemistry and technological interest. Certain oxynitride crystal structures allow very significant compositional variation through extensive Si/N exchange for Al/O, which implies a degree of atomic ordering. In this study, solid-state 29Si MAS NMR and variable field 1D and 2D 27Al MAS NMR measurements are combined with density functional theory calculations of both the structural and NMR interaction parameters for various points across the Y4Si2O7N2–Y4Al2O9 compositional range. This series provides numerous possibilities for significant variation of atomic ordering in the local ditetrahedral (Si,Al)2O7–xNx units. The two slightly structurally inequivalent aluminum sites in Y4Al2O9 are unambiguously assigned to the observed resonances. Computational findings on Y4Si2O7N2 demonstrate that the single observed 29Si NMR resonance covers a range of local inequivalent silicon environments. For the first time, the MAS NMR and neutron diffraction data from the Y4SiAlO8N structure have been directly reconciled, thus establishing aspects of atomic order and disorder that characterize this system. This comparison suggests that, although the diffraction data indicates long-range structural order supporting a highly crystalline character, the short-range information afforded by the solid-state NMR measurements indicates significant atomic disorder throughout the (Si,Al)2O7–xNx units.
1932-7447
23976-23987
Seymour, V.R.
13587906-718e-4005-b7d6-bc7d522b5594
Griffin, J.M.
6dbd9cb3-45da-4e26-ba03-67d7b1c332d7
Griffith, B.E.
f1686da7-1bc7-4782-a515-88968a5b3074
Page, S.J.
f28c872a-ca94-498f-8d4f-77e2bdc48b60
Iuga, D.
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Hanna, J.V.
fe8416bd-4401-44b9-8155-d1330234bef9
Smith, M.E.
abd04fbf-5f56-459d-89ec-e51ab2598c09
Seymour, V.R.
13587906-718e-4005-b7d6-bc7d522b5594
Griffin, J.M.
6dbd9cb3-45da-4e26-ba03-67d7b1c332d7
Griffith, B.E.
f1686da7-1bc7-4782-a515-88968a5b3074
Page, S.J.
f28c872a-ca94-498f-8d4f-77e2bdc48b60
Iuga, D.
280c6d9a-aeca-4bf7-8510-b4588556d530
Hanna, J.V.
fe8416bd-4401-44b9-8155-d1330234bef9
Smith, M.E.
abd04fbf-5f56-459d-89ec-e51ab2598c09

Seymour, V.R., Griffin, J.M., Griffith, B.E., Page, S.J., Iuga, D., Hanna, J.V. and Smith, M.E. (2020) Improved understanding of atomic ordering in Y4SixAI2-xO9-xNx materials using a combined solid-state NMR and computational approach. Journal of Physical Chemistry C, 124 (43), 23976-23987. (doi:10.1021/acs.jpcc.0c07281).

Record type: Article

Abstract

Ceramics based around silicon aluminum oxynitrides are of both fundamental structural chemistry and technological interest. Certain oxynitride crystal structures allow very significant compositional variation through extensive Si/N exchange for Al/O, which implies a degree of atomic ordering. In this study, solid-state 29Si MAS NMR and variable field 1D and 2D 27Al MAS NMR measurements are combined with density functional theory calculations of both the structural and NMR interaction parameters for various points across the Y4Si2O7N2–Y4Al2O9 compositional range. This series provides numerous possibilities for significant variation of atomic ordering in the local ditetrahedral (Si,Al)2O7–xNx units. The two slightly structurally inequivalent aluminum sites in Y4Al2O9 are unambiguously assigned to the observed resonances. Computational findings on Y4Si2O7N2 demonstrate that the single observed 29Si NMR resonance covers a range of local inequivalent silicon environments. For the first time, the MAS NMR and neutron diffraction data from the Y4SiAlO8N structure have been directly reconciled, thus establishing aspects of atomic order and disorder that characterize this system. This comparison suggests that, although the diffraction data indicates long-range structural order supporting a highly crystalline character, the short-range information afforded by the solid-state NMR measurements indicates significant atomic disorder throughout the (Si,Al)2O7–xNx units.

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YAM_2019_JPCC_Revised - Accepted Manuscript
Restricted to Repository staff only until 15 October 2021.
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Accepted/In Press date: 5 October 2020
e-pub ahead of print date: 15 October 2020
Published date: 29 October 2020

Identifiers

Local EPrints ID: 445248
URI: http://eprints.soton.ac.uk/id/eprint/445248
ISSN: 1932-7447
PURE UUID: c26cab80-09ce-4869-b779-7f988dd54490

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Date deposited: 26 Nov 2020 17:31
Last modified: 26 Nov 2020 17:32

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Contributors

Author: V.R. Seymour
Author: J.M. Griffin
Author: B.E. Griffith
Author: S.J. Page
Author: D. Iuga
Author: J.V. Hanna
Author: M.E. Smith

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