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Abstract: In this work, perovskite BaBiO3−δ disk membranes were synthesized with the molar ratio (z) of BiO1.5 to BaO between 0.5 and 3 at varying sintering temperatures. Disk membranes with z > 1.33, associated with a lower amount of Bi-rich perovskite phase, showed mechanically weak properties while membranes with z ≤1 showed superior stability at temperatures in excess of 800°C. The best performance was obtained for the z = 0.86 disk membrane, reaching oxygen fluxes of 1.2mlmin−1 cm−2 at 950°C. This was attributed to the higher sintering temperature and the formation of oxygen deficient phase of BaBiO3−δ perovskite. For gas testing temperatures above 800°C, it was found that the oxygen permeation was limited by both bulk diffusion and surface kinetics as oxygen flux did not increase proportionally to the inverse of membrane thickness reduction. Further analysis showed that the activation energy for oxygen ionic transport changed at 800°C, however the z = 1 sample displayed the opposite trend from other compositions, indicating the formation of more oxygen vacancies in the crystal lattice. Mechanically stable disk membranes exposed to thermal cycling tests resulted in crystal structure instability of the pure perovskite (z = 1) and loss of oxygen vacancies while the z < 1 sample was relatively stable. Conversely, z >1 sample showed superior thermal cycling and crystal structure stability. [Copyright &y& Elsevier]

Abstract: Hollow fibre membranes of mixed conducting perovskite La0.6Sr0.4Co0.2Fe0.8O3 (LSCF) were prepared via the combined phase inversion and sintering technique. The fibres were tested for air separation with a home-made reactor under the oxygen partial pressure gradient generated by the air/He streams. Some fibres were in situ activated by introducing methane in the He sweeping gas at high temperatures. The activated membranes with new morphology were created by transforming the inner densified surface layer to a porous structure. Compared to the original membranes, the activated gave appreciable higher oxygen fluxes. At 800°C, the oxygen fluxes were increased by a factor of 10 after activation was carried out at 1000°C for 1h. [Copyright &y& Elsevier]