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

Dual-phase membranes are increasingly attracting attention as a solution for developing stable oxygen permeation membranes. Ce0.8Gd0.2O2-delta -Fe3-xCoxO4 (CGO-F(3 x)CxO) composites are one group of promising candidates. This study aims to understand the effect of the Fe/Coratio, 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/cm(2) .s at 1000 degrees C and 850 degrees C, respectively, of the 85CGO-FC2O composite, which is comparable oxygen permeation flux reported previously.

Automated summary

This study investigates the effect of the Fe/Co ratio on the microstructure and performance of Fe3-xCoxO4 composites. Results show that the presence of iron in the composite leads to the formation of additional phases with spinel or garnet structures, which contribute to electronic conductivity. The presence of both types of cations is crucial for the formation of a composite structure, allowing for efficient electronic and ionic conduction. The maximum oxygen flux of the composite is 0.16 and 0.11 mL/cm(2) .s at 1000°C and 850°C, respectively, comparable to previous reports.