XANES analyses on minor elements and X–ray single crystal structure analyses of Ce– and Nb–perovskite

Abstract

Structural analysis of Ce- and Nb-perovskites containing Fe, Zr, Nb, and rare earth elements (REEs) in CaTiO3 perovskite was performed using single-crystal X-ray diffraction and X-ray absorption near-edge structure (XANES) analyses. Based on chemical analysis results, XANES measurements and the site-occupation of elements at A- and B-sites showed the chemical formula: (Ca-0.817(2+) REE0.0873+Na0.081+Sr0.0052+Th0.0034+)(0.993)1(.998+) (Ti-0.941(4+))Na0.0205+La0.0153+Sr0.0032+)(0.996)(2.008+) (Ti0.7304+Nb0.1225+Fe0.1083+Al0.0203+Zr0.0094+V0.0085+)(0.997)(3.990+) O-3 for Nb-perovskite. In Ce- and Nbperovskites, the total charges at the A- and B-sites achieved near-ideal divalent and tetravalent states such as Ca2+ Ti4+ O-3, respectively, due to complex elemental substitutions. Local distortions around Ti in the perovskite solid solutions were greater, and the pre-edge features of the Ti atoms in Ce- and Nb-perovskites were different from those in pure CaTiO3. The valence states and local structures of Fe in Ce- and Nb-perovskites were significantly different. The existence of divalent Fe2+ at the B-site in Ce-perovskite was confirmed. It is presumed that the displacement ellipsoids of all atoms and local irregularities in Ce-perovskite increase owing to the radiative decay of the actinoid element Th. We reconfirmed that the composition and three-dimensional structure of perovskite-type structures were flexible and caused various electrical, structural changes.