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 CaTiO 3 perovskite was performed using single – crystal X – ray di ff raction 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 2+0.817 REE 3+0.087 Na +0.081 Sr 2+0.005 Th 4+0.003 ) 1.998+0.993 (Ti 4+0.941 Nb 5+0.017 Fe 3+0.013 V 5+0.010 Fe 2+0.007 Sc 3+0.006 Zn 2+0.005 Al 3+0.002 Ge 4+0.001 W 6+0.001 ) 3.996+1.003 O 3 for Ce – perovskite and (Ca 2+0.937 Ce 3+0.021 Na +0.020 La 3+0.015 Sr 2+0.003 ) 2.008+0.996 (Ti 4+0.730 Nb 5+0.122 Fe 3+0.108 Al 3+0.020 Zr 4+0.009 V 5+0.008 ) 3.990+0.997 O 3 for Nb – perovskite. In Ce – and Nb – perovskites, the total charges at the A – and B – sites achieved near – ideal divalent and tetravalent states such as Ca 2+ Ti 4+ 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 di ff erent from those in pure CaTiO 3 . The valence states and local structures of Fe in Ce – and Nb – perovskites were signi fi cantly di ff erent. The existence of divalent Fe 2+ at the B – site in Ce – perovskite was con fi rmed. 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 recon fi rmed that the composition and three – dimensional structure of perovskite – type structures were fl exible and caused various electrical, structural changes.