Decomposition pathway of cubic Ba_0.5Sr_0.5Co_0.8Fe_0.2O_{3 ?#xa0;¦Ä} between 700 ¡ãC and 1000 ¡ãC analyzed by electron microscopic techniques

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• 作者：P. Mü ; ller^a ; ^{philipp.mueller@kit.edu} ; H. Stö ; rmer^a ; ¹ ; ^{heike.stormer@kit.edu} ; L. Dieterle^a ; ¹ ; ^{levin.dieterle@kit.edu} ; C. Niedrig^b ; ^{christian.niedrig@kit.edu} ; E. Ivers-Tiffé ; e^b ; ^{ellen.ivers@kit.edu} ; D. Gerthsen^a ; ¹ ; ^{dagmar.gerthsen@kit.edu}
• 关键词：BSCF ; Transmission electron microscopy ; Perovskites ; Phase stability ; Mixed conductor
• 刊名：Solid State Ionics
• 出版年：2012
• 出版时间：5 January, 2012
• 年：2012
• 卷：206
• 期：Complete
• 页码：57-66
• 全文大小：2309 K

文摘

Mixed ionic-electronic conductors and, among those, in particular Ba_0.5Sr_0.5Co_0.8Fe_0.2O_{3 ?#xA0;¦Ä} (BSCF5582) with high oxygen ion conductivity are of great interest for oxygen separation membranes. To study the decomposition of BSCF5582 under application-relevant conditions, BSCF5582 bulk samples were annealed at temperatures between 700 ¡ãC and 1000 ¡ãC and investigated by X-ray diffractometry and various electron microscopic techniques. Beside the verification of the formation of a hexagonal phase, an additional phase with plate-like morphology and trigonal crystal structure is observed. While the crystallization of the hexagonal phase is limited to temperatures below 830 ¡ãC, the plate-like phase is detected up to 900 ¡ãC annealing. The chemical composition of the hexagonal and plate-like phases was analyzed by energy dispersive X-ray spectroscopy. The plate-like phase is characterized by a cobalt enrichment and strontium depletion whereas the barium concentration remains unchanged with respect to the cubic BSCF matrix. The kinetics of the decomposition at 800 ¡ãC of the cubic phase was studied by annealing treatments up to 1350 h. The plate-like phase shows fast precipitation whereas the formation of the hexagonal phase was found to be significantly slower.