Novel Approach for Developing Dual-Phase Ceramic Membranes for Oxygen Separation through Beneficial Phase Reaction

A novel method based on beneficial phase reaction for developing composite membranes with high oxygen permeation flux and favorable stability was proposed in this work. Various Ce_0.8Sm_0.2O_2-δ (SDC) + SrCO₃+Co₃O₄ powders with different SDC contents were successfully fabricated into membranes through high temperature phase reaction. The X-ray diffraction (XRD) measurements suggest that the solid-state reaction between the SDC, SrCO₃ and Co₃O₄ oxides occurred at the temperature for membrane sintering, leading to the formation of a highly conductive tetragonal perovskite phase Sm_xSr_1-xCoO_3-δ. The morphology and elemental distribution of the dual-phase membranes were characterized using back scattered scanning electron microscopy and energy dispersive X-ray spectroscopy (BSEM-EDX). The oxygen bulk diffusivity and surface exchange properties of the materials were investigated via the electrical conductivity relaxation technique, which supported the formation of conductive phases. The SDC+20 wt % SrCO₃+10.89 wt % Co₃O₄ membrane exhibited the highest permeation flux among the others, reaching 0.93 mL cm^-2 min^-1 [STP = standard temperature and pressure] under an air/helium gradient at 900 °C for a membrane with a thickness of 0.5 mm. In addition, the oxygen permeation flux remained stable during the long-time test. The results demonstrate the beneficial phase reaction as a practical method for the development of high-performance dual-phase ceramic membranes.