Distribution change of oxygen vacancies in layered perovskite type(Sr, La)n+1FenO3n+1 (n=3)

•Distribution change of oxygen vacancies is appeared at approximately 775 °C.•The distribution change with no structure phase transition is the first observation.•The vacancy distribution change affects the ion conductivity of the SLF4310.

To elucidate characteristic oxygen vacancy formation in layered perovskite (Sr, La)n+1FenO3n+1 with the perovskite layer number: n=3, oxygen vacancy content δ of the (Sr0.775La0.225)4Fe3O10−δ (SLF4310) was investigated using a titration technique and a thermogravimetric analysis. The equilibrium constant K for the reduction reaction: Oo×+2FeFe∙ (Fe4+)=1/2O2+Vo∙∙+2FeFe×(Fe3+) was estimated using the vacancy content δ. The Arrhenius plot of the K reveals slope change at approximately 775 °C. From the Rietveld analysis, the oxygen vacancies are the most remarkable at the O2 (O4) sites at lower (higher) temperatures than about 800 °C, which temperature is approximately comparable with that of slope change in the K. These facts mean that distribution of vacancy sites in the SLF4310 changes at approximately 775 °C, accompanying no structural phase transition. The vacancy distribution change affects to the ion conductivity of the SLF4310.

Graphical abstractCrystal structure of (Sr0.775La0.225)4Fe3O10−δ (SLF4310) at 1000 °C.Figure optionsDownload full-size imageDownload as PowerPoint slide