FE K-EDGE X-RAY-ABSORPTION (XANES EXAFS) SPECTROSCOPIC STUDY OF THE NONSTOICHIOMETRIC SRFE1-XSNXO3-Y SYSTEM/

Local structure refinement of the SrFe1-xSnxO3-y (x = 0.00, 0.25, 0.50 and 0.75) system has been carried out with Fe K-edge X-ray absorption spectroscopic studies. It is found out that the Fe ions are placed in two different symmetric sites, such as tetrahedral and octahedral sit es in the compounds from Fe K-edge X-ray absorption near edge structur es. Small absorption peaks of the electric quadrupole-allowed transiti ons appear at the pre-edge region of about 7112 eV, due to the existen ce of Fe ions in the tetrahedral and octahedral sites. Two different a bsorption peaks of 1s --> 4p dipole-allowed transition appear on the e nergy region between 7126 and 7131 eV. The peaks correspond to 1s --> 4p main transition of Fe ions in tetrahedral and octahedral sites and also to 1s --> 4p transition followed by the shakedown process of liga nd to metal charge transfer. From extended X-ray absorption fine struc ture study, the interatomic distance of the Fe-O bond increases with t he increasing amount of Sn atom. The interatomic distance of the Fe-Fe bond is smaller than that of the Fe-Sn bond, which shows that the sub stituted Sn atom is positioned to a longer distance of about 0.1 Angst rom from the X-ray absorbing Fe atom. (C) 1998 Elsevier Science Ltd. A ll rights reserved.