Local structure and polarization resistance of Ce doped SrMnO_3 using extended x-ray fine structure analysis

摘要

Changes to the local structure of Sr and Mn atoms in Sr_(1-x)Ce_xMnO_3 (SCM) according to increasing Ce content and the effect of the structural change on the polarization resistance of SCM were investigated. The reduction of manganese was confirmed by the absorption edge shift of the Mn K-edge toward lower energies. The noise of oscillation in extended X-ray absorption fine structure k~3 χ data at Mn K-edge reveals the distortion of the local structure of Mn atoms, and the peak that indicates the bonding length of Mn-O, Sr/Ce, and -Mn decreased with the addition of Ce content in Fourier transformations of the Mn K-edge. The distortion of the local structure at Mn atoms was affected by the reduced manganese ions having larger ionic radii than Mn~(4+). Meanwhile, few distortions of local atomic structures of Sr atoms occurred, and the average nearest neighboring distances of Sr-O and Sr-Mn are ～2.13 Å and ～2.95 Å, respectively. The average bonding lengths of the Ce-O and Ce-Mn increased because the ionic radius of substituted Ce ion with 12 coordination number is smaller than that of Sr ion, which leads the reduction of Mn ions and the distortion of local structure at the substituted A-site. Therefore, we reasoned that the distortion of the local atomic structure at Mn atoms in MnO_6 and Ce atoms in A-site is one of the causes for interrupting oxygen ion transfers as a geometric factor, which results in an increase in the polarization resistance of SCM within the Ce composition range from 10mol. % to 30mol. %.