Thermochemical stability of Fe- and co-functionalized perovskite-type SrTiO3 oxygen transport membrane materials in syngas conditions

Abstract The materials typically used for oxygen transport membranes, Ba 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3−δ (BSCF) and La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3 (LSCF) tend to decompose due to their low thermochemical stability under reducing atmosphere. Fe- and Co-doped SrTiO 3 (SrTi 1-x-y Co x Fe y O 3-δ , x + y ≤ 0.35) (STCF) materials showing an oxygen transport comparable to LSCF have great potential for application in ion-transport-devices. In this study, the thermochemical stability of pure perovskite-structured STCF was investigated after annealing in a syngas atmosphere at 600–900 °C. The phase composition of the materials after annealing was characterized by means of X-ray diffraction (XRD). The thermodynamic activities of SrO, FeO, and CoO in the STCF materials were evaluated using Knudsen effusion mass spectrometry (KEMS). Co-doped SrTiO 3 (STC) materials were not stable after annealing in the syngas atmosphere above 5 mol% Co-substitution. Ruddlesden-Popper-like phases and SrCO 3 were detected after annealing at 600 °C. In contrast, Fe substitution (STF) showed good stability after annealing in syngas upto 35 mol% substitution.