Role of Fe/Co Ratio in Dual Phase Ce0.8Gd0.2O2−δ–Fe3−xCoxO4 Composites for Oxygen Separation

Liudmila Fischer*, Ke Ran, Christina Schmidt, Kerstin Neuhaus, Stefan Baumann*, Patrick Behr, Joachim Mayer, Henny J.M. Bouwmeester, Arian Nijmeijer, Olivier Guillon, Wilhelm A. Meulenberg

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

1 Citation (Scopus)
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Dual-phase membranes are increasingly attracting attention as a solution for developing stable oxygen permeation membranes. Ce0.8Gd0.2O2−δ–Fe3−xCoxO4 (CGO-F(3−x)CxO) composites are one group of promising candidates. This study aims to understand the effect of the Fe/Co-ratio, i.e., x = 0, 1, 2, and 3 in Fe3−xCoxO4, on microstructure evolution and performance of the composite. The samples were prepared using the solid-state reactive sintering method (SSRS) to induce phase interactions, which determines the final composite microstructure. The Fe/Co ratio in the spinel structure was found to be a crucial factor in determining phase evolution, microstructure, and permeation of the material. Microstructure analysis showed that all iron-free composites had a dual-phase structure after sintering. In contrast, iron-containing composites formed additional phases with a spinel or garnet structure which likely contributed to electronic conductivity. The presence of both cations resulted in better performance than that of pure iron or cobalt oxides. This demonstrated that both types of cations were necessary to form a composite structure, which then allowed sufficient percolation of robust electronic and ionic conducting pathways. The maximum oxygen flux is jO2 = 0.16 and 0.11 mL/cm2·s at 1000 °C and 850 °C, respectively, of the 85CGO-FC2O composite, which is comparable oxygen permeation flux reported previously.

Original languageEnglish
Article number482
Number of pages17
Issue number5
Early online date29 Apr 2023
Publication statusPublished - May 2023


  • ceramic materials
  • dual phase oxygen transport membrane
  • microstructure
  • mixed ionic-electronic conductors
  • optimization
  • oxygen permeation
  • spinel-type ferrite


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