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Yosuke Takahashia, b, 
, 
, Akihiro Kawaharab, Takehiro Suzukib, Masayoshi Hiranoc and Woosuck Shina, d
Abstract
The substitution of A-site alkali ions and B-site transition metal ions of the perovskite oxide oxygen-permeating membrane system of La1−xSrxTi1−yFeyO3−δ, (LSTF) has been studied for their application to the partial oxidation of methane to syngas. Both the substitution of Fe for Ti, and the substitution of Sr for La increased the p-type electronic and oxygen ionic conductivities to 155 and 0.47 S cm− 1 respectively. From 800 to 1000 °C, the temperature dependence of conductivity has been studied, and the thermal activation energy of the p-type electronic conductivity of La0.6Sr0.4Ti0.1Fe0.9O3−δ was found to be 38 kJ/mol and those of the ionic conductivity of La0.6Sr0.4Ti1−yFeyO3−δ (y = 0.7 and 0.9) were 11 and 20 kJ/mol. The thermal expansion coefficients of LSTF were varied from 10.8 to 17.0 (× 10− 6/K− 1) by increasing the Fe substitution. La0.6Sr0.4Ti0.3Fe0.7O3−δ was the optimized composition with a good trade-off of the high ion conductivity, 0.07 S cm− 1, and good matching of the thermal expansion coefficient, 12.4 × 10− 6/K− 1. It has been tested for the partial oxidation of methane to syngas and shows a high oxygen permeation rate of 13.8 cm3/min/cm2 at 1000 °C or 10.5 cm3/min/cm2 at 900 °C. In addition, High values of CH4 conversion and CO selectivity were confirmed at 900 °C, 60.0% and 99.9% respectively.
Keywords: Ceramic membrane; LaSrTiFeO3 perovskite oxide; Oxygen permeation
