Investigation on the phase stability of cubic perovskite BaCo0.7Fe0.2Nb0.1O3-δ oxygen-permeable membrane

The phase stability of the cubic perovskite-type oxide BaCo0.7Fe0.2Nb0.1O3−δ (BCFNO) has been examined by means of X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). And, the timescale on the second phases has been established by using the TOPAS 4.2. Compared with Ba0.5Sr0.5Co0.8Fe0.2O3−δ (BSCFO), for samples annealed at T = 1023 K for t = 64 d, the rhombohedral and hexagonal phases formed on the surface of cubic perovskite BCFNO surface simultaneously and the amount of them is smaller. As for the rhombohedral phase, it comes out firstly along the grain boundary, and whose amount in equilibrium is about 5％. In contrast to the rhombohedral phase, the hexagonal phase is more likely to form at lower temperature which lead to the microcracks. In brief, obtaining the eligible phase stability is crucial for the industrial application of the oxygen permeation membrane.