Journal
ACTA MATERIALIA
Volume 234, Issue -, Pages -Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.actamat.2022.118034
Keywords
Oxygen transport membrane; Emerging phase; Interface segregation; Valence states; STEM-HAADF; EELS; EDXS
Funding
- Deutsche Forschungsge-meinschaft [387282673]
- Bundesministerium f?r Bildung und Forschung (NEUROTEC)
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This study characterized the newly formed phase inside dual-phase oxygen transport membranes (DP-OTMs) using advanced transmission electron microscopy techniques. The results showed that the newly formed phase is primarily surrounded by the existing phase, reducing non-solute segregation at grain boundaries. The study also observed the crystal structure of interfaces between the two phases.
The in situ generated emerging phase inside the dual-phase oxygen transport membranes (DP-OTMs) plays a crucial role in boosting the overall performance of DP-OTMs. However, its detailed structure and properties are still not fully understood. Utilizing advanced transmission electron microscopy (TEM) techniques, the emerging phase GdxCe1-xFeyCo1-yO3-delta (GCFCO) inside the CexGd1-xO2-delta-FeCo2O4 (CGO-FC2O) OTMs was successfully characterized at the atomic scale. The newly formed GCFCO is primarily surrounded by the CGO, and contributes to a significant reduction of non-solute segregation at the CGO grain boundaries. Electronic characteristics of the GCFCO shows a sensitive dependence on its chemical composition, including the valence state of Ce and Fe as well as the oxygen vacancies. Additional CGO-GCFCO interfaces were introduced, where almost intact crystal structures were observed with slight Gd and Co segregation similar to 1 nm at the edges. Approaching the interface, on the CGO side, only a minimum drop of the Ce valence was determined. On the GCFCO side, mixed Ce3+ and Ce4+ are partially occupying the Gd sites, while Fe and Co valence stay constant until the edge. Our study provides novel insight into the phase information within CGO-FC2O composites, which paves the path towards superior performance of various DP-OTMs. (C) 2022 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
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