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.

Crystal structure of (Sr0.775La0.225)4Fe3O10−δ (SLF4310) at 1000 °C.Figure optionsDownload as PowerPoint slide