Defects and disorder in apatite-type silicate oxide ion conductors: implications for conductivity

Fuller, Chloe A.; Gutmann, Matthias J.; Ling, Chris D.; Wang, Chun-Hai; Zhang, Weiguo; Halasyamani, P. Shiv; Evans, Ivana Radosavljevic; Evans, John S.O.

Abstract

The structure and composition of La-silicate apatite oxide ion conductor, La10Si6O27, in which the types of defects it contains are controversial, has been thoroughly investigated. Large crystals were grown using the floating zone method, and their structure was characterised by X-ray and neutron single crystal diffraction and second harmonic generation measurements. Structure refinements reveal extensive positional disorder on the oxygen substructure, the presence of La vacancies and no evidence of sites occupied by excess oxide ions. The actual composition of the crystal was determined through SEM-EDX and density measurements and was found to be La9.64Si5.77O26, differing significantly from the nominal composition but in agreement with the structure refinements. Structural models considering the actual composition, the disorder on the O sublattice, and local relaxations around these defects were able to reproduce the key features of the diffuse scattering observed in single crystal neutron diffraction patterns.

Citation

Fuller, C. A., Gutmann, M. J., Ling, C. D., Wang, C., Zhang, W., Halasyamani, P. S., …Evans, J. S. (2022). Defects and disorder in apatite-type silicate oxide ion conductors: implications for conductivity. Journal of Materials Chemistry A: materials for energy and sustainability, 10(27), https://doi.org/10.1039/d2ta02328h

• Journal Article Type: Article
• Acceptance Date: Jun 20, 2022
• Online Publication Date: Jun 21, 2022
• Publication Date: 2022
• Deposit Date: Jul 21, 2022
• Publicly Available Date: Jul 22, 2022
• Journal: Journal of Materials Chemistry A
• Print ISSN: 2050-7488
• Electronic ISSN: 2050-7496
• Publisher: Royal Society of Chemistry
• Peer Reviewed: Peer Reviewed
• Volume: 10
• Issue: 27
• DOI: https://doi.org/10.1039/d2ta02328h
• Public URL: https://durham-repository.worktribe.com/output/1197162