Structure and property relationship in the mixed-conducting Sr-Fe-Co-O system.
Mixed-conducting ceramic oxides have potential uses in high-temperature electrochemical applications such as solid oxide fuel cells, advanced batteries, sensors, and oxygen-permeable membranes. The Sr-Fe-Co-O system combines high electronic/ionic conductivity with appreciable oxygen permeability at elevated temperatures. Dense ceramic membranes made of this material can be used to separate high-purity oxygen from air without the need for external electrical circuitry, or to partially oxidize methane to produce syngas. Samples of Sr{sub 2}Fe{sub 3{minus}x}Co{sub x}O{sub y} (with x = 0, 0.6, 1.0, and 1.4) were prepared by solid-state reaction in atmospheres with various oxygen partial pressures (pO{sub 2}) and were characterized by X-ray diffraction, scanning electron microscopy, and electrical conductivity measurements. Phase components of the samples are dependent on cobalt concentration and synthesis pO{sub 2}. Total conductivity increases with increasing temperature and cobalt content in the material. Higher ionic transference numbers have been observed in samples with lower cobalt contents. Current-voltage characteristics determined in a gas-tight cell indicate that a bulk effect, rather than a surface exchange effect, is the main limiting factor for oxygen permeation through membranes made of Sr{sub 2}Fe{sub 2}CoO{sub y}. Oxygen permeability measurements at various temperatures showed that oxygen permeability increases with increasing temperature, as expected. At 900 C, an oxygen permeation flux of 2.5 scc{center_dot}cm{sup {minus}2}{center_dot}min{sup {minus}1} was obtained for a Sr{sub 2}Fe{sub 2}CoO{sub y} disk of 2.9 mm thickness.
- Research Organization:
- Argonne National Lab., IL (US)
- Sponsoring Organization:
- US Department of Energy (US)
- DOE Contract Number:
- W-31109-ENG-38
- OSTI ID:
- 10561
- Report Number(s):
- ANL/ET/CP-95329
- Country of Publication:
- United States
- Language:
- English
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