Chemical stability of La0.6Sr0.4CoO3− δ in oxygen permeation applications under exposure to N2 and CO2
Abstract Phase stability and chemical reactivity of (La 0.6 Sr 0.4 ) 0.99 CoO 3− δ (LSC64) was tested in oxidative (pO 2  = 0.21 atm) and slightly reducing conditions (pO 2  ~ 10 − 5  atm), as well as in carbon dioxide (pO 2  ~ 10 − 4  atm) to evaluate the material performance for oxygen separation technologies. Thin film LSC64 oxygen separation membranes (20–30 μm) were manufactured and electrochemical performance was evaluated at a range of temperatures with either nitrogen or CO 2 purged on the permeate side of the membrane. Material stability was also investigated by high temperature X-ray diffraction, TGA and conductivity measurements in air, N 2 and CO 2 . Under mild reduction LSC64 partly decomposes to a K 2 NiF 4 -type phase (i.e. (La,Sr) 2 CoO 4 ), and Co-oxide, and under high pCO 2 forms SrCO 3 . The latter is found to impair membrane performance. Electrical properties and oxygen permeation (jO 2 ) in thin membranes depend on the thermal and chemical history of the samples. A flux of 4–6 Nml min − 1  cm − 2 in the temperature range of 800–900 °C was demonstrated for optimized membranes and conditions.