Anisotropic oxygen diffusion at low temperature in perovskite-structure iron oxides

作者：Inoue Satoru; Kawai Masanori; Ichikawa Noriya; Kageyama Hiroshi; Paulus Werner; Shimakawa Yuichi^*

来源：Nature Chemistry, 2010, 2(3): 213-217.

DOI：10.1038/NCHEM.547

Oxygen-ion conduction in transition-metal oxides is exploited in, for example, electrolytes in solid-oxide fuel cells and oxygen-separation membranes, which currently work at high temperatures. Conduct at low temperatures is a key to developing further utilization, and an understanding of the structures that enable conduction is also important to gain insight into oxygen-diffusion pathways. Here we report the structural changes observed when single-crystalline, epitaxial CaFeO(2.5) thin films were changes into CaFeO(2) by low-temperature reductions with CaH(2). During the reduction process from the brownmillerite CaFeO(2.5) into the infinite-layer structure of CaFeO(2), some of the oxygen atoms are released from and others are rearranged within the perovskite-structure framework. We evaluated these changes and the reaction time they required, and found two oxygen diffusion pathways and the related kinetics at low temperature. The results demonstrate that oxygen diffusion in the brownmillerite is highly anisotropic, significantly higher along the lateral direction of the tetrahedral and octahedral layers.

• 出版日期2010-3