LOCAL-STRUCTURE REFINEMENT OF THE BAFE1-XSNXO3-Y SYSTEM WITH FE K-EDGE X-RAY-ABSORPTION (XANES EXAFS) SPECTROSCOPY/

Local structure refinement of the BaFe1-xSnxO3-y system (x=0.00-0.50) has been carried out with Fe K-edge xray absorption spectroscopic stud ies. It is found out that the Fe ions are placed in two different symm etric sites such as tetrahedral and octahedral sites in the compounds by comparison with Fe K-edge x-ray absorption near edge structure (XAN ES) spectrum of the gamma-Fe2O3 compound as a reference. Small absorpt ion peaks of dipole-forbiden transitions appear at a pre-edge region o f 7111 eV due to the existence of Fe ions in the tetrahedral and octah edral sites. The peak intensity deceases with the substitution amount of Sn ion. Three different absorption peaks of 1s-->4p dipole-allowed transition appear on the energy region between 7123 and 7131 eV. The p eaks correspond to 1s-->4p main transition of Fe ions in tetrahedral a nd octahedral sites and 1s-->4p transition followed by the shakedown p rocess of ligand to metal charge transfer. The bond distances between Fe ions in the tetrahedral site and nearest neighboring oxygen atom (F e-4O), and those in octahedral site (Fe-6O) are determined with the ex tended x-ray absorption fine structure (EXAFS) analysis. Two different interatomic distances increase with the substitution amount of Sn ion and also the bond lengths of Fe-4O are shorter than those of Fe-6O in all compounds.