Structural analysis of oxide ion conductor, Ba2-xSrxIn2O5 and Ba2In2-xGaxO5 - Significance of synchrotron X-ray diffraction at high temperatures

High temperature synchrotron X-ray diffraction measurements have been performed on Ba2-xSrxIn2O5 and Ba2In2-xGaxO5, which exhibits two kinds of structural phase transition and high oxide ion conductivity at the high temperature phase. It has been revealed that the synchrotron X-ray diffraction with high sensitivity and resolution is necessary to detect any slight distortion from ideal cubic perovskite in cation substituted Ba2In2O5 system. By using synchrotron X-ray diffraction, the slight distortion from ideal cubic perovskite in Ba2In2-xGaxO5, which could not be observed by using Cu Kα X-ray diffraction, has been clarified. The larger and smaller distortions have been observed with an increase of Sr and Ga content, respectively, which can be explained from the viewpoint of variation of the tolerance factor.