Overlayer deposition-induced control of oxide ion concentration in SrFeCoO oxygen sponges

Controlling the oxide ion (O 2− ) concentration in oxides is essential to develop advanced ionic devices, i.e. solid oxide fuel cells, smart windows, memory devices, energy storage devices, and so on. Among many oxides several transition metal (TM)-based perovskite oxides show high oxide ion conduct...

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Published in:RSC advances 2021-09, Vol.11 (51), p.3221-32215
Main Authors: Lee, Joonhyuk, Kim, Younghak, Cho, Jinhyung, Ohta, Hiromichi, Jeen, Hyoungjeen
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Summary:Controlling the oxide ion (O 2− ) concentration in oxides is essential to develop advanced ionic devices, i.e. solid oxide fuel cells, smart windows, memory devices, energy storage devices, and so on. Among many oxides several transition metal (TM)-based perovskite oxides show high oxide ion conductivity, and their physical properties show high sensitivity to the change of the oxide ion concentration. Here, the change in the oxide ion concentration is shown through the overlayer deposition on the SrFe 0.5 Co 0.5 O 2.5 (SFCO) oxygen sponge film. We grew SFCO films followed by the deposition of two kinds of complex oxide films under exactly the same growth conditions, and observed the changes in the crystal structure, valence states, and magnetic ground states. As the NSMO overlayer grows, strong evidence of oxidation at the O K edge is shown. In addition, the Fe 4+ feature is revealed, and the electron valence state of Co increased from 3 to 3.25. The oxide ion concentration of SFCO changes during layer growth due to oxidation or reduction due to differences in chemical potential. The present results might be useful to develop advanced ionic devices using TM-based perovskite oxides. We form flat oxide-interfaces, i.e. manganite- and titanate-oxygen sponges, and observe peculiar oxygen transport behaviors relying on chemical potential difference at the interfaces. Oxygen transport into oxygen-sponge leads weak ferromagnetism.
ISSN:2046-2069
DOI:10.1039/d1ra06378b