Fe-doped La1-xSrxGaO3 exhibits a high conductivity (∼1 S/cm) and a high oxygen permeation rate. In particular, the highest conductivity and the oxygen permeating rate were attained at La0.7Sr0.3Ga0.6Fe0.4O3 (LSGF). Although a surface catalyst is required, oxygen permeation rate from air to Ar was as high as 2.5 cm3 std/min cm2 at 1273 K and 0.3 mm membrane thickness. Oxygen permeation rate from air to Ar increased in the following order, La0.6Sr0.4CoO3 > La0.9Sr0.1CoO3 = Sm0.5Sr0.5CoO3 ≫ Sm0.6Sr0.4CoO3, as the surface catalyst. Since the p02 gradient becomes larger, the oxygen permeation rate drastically increased by changing from air-Ar to CH4-air condition. The products were only CO and H2, having a molar ratio (H2/CO ratio) of almost two. Electronic hole conduction was only observed in LSGF polarization measurement and the oxide ion conductivity estimated is as high as s = 0.6 S cm-1 at 1073 K. At high po2, the main defect in LSGF is Oi″ and FeFė and at intermediate po2, concentration of FeFė is balanced with that of Oi″. The estimated transport number of oxide ion was ca. 0.6, which is in a good agreement with that estimated by the electromotive force in H2-O2 gas concentration cells.
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Renewable Energy, Sustainability and the Environment
- Surfaces, Coatings and Films
- Materials Chemistry