Evolution of crystal and electronic structures of Sr2CuO3 upon fluorination reaction

Cu K-edge X-ray absorption spectroscopic (XAS) analyses have been systemati cally performed to examine the evolution of crystal and electronic structur es of Sr2CuO3 upon fluorination. From the Cu K-edge X-ray absorption near-e dge structure (XANES) results presented hen, it becomes clear that the fluo rination process leads to hole doping of the CuO2 layer as well as to struc tural modification from the square planar CuO4 cluster of Sr2CuO3 to the oc tahedral CuO4F2 one of Sr2CuO2F2+x. In addition, the comparative extended X -ray absorption fine structure (EXAFS) analyses for Sr2CuO2F2+x and the ref erence La2CuO4 reveal that the apical copper-ligand bond has a larger bond distance and a greater structural disorder in the former than in the latter , Based on these findings, it can be concluded that fluorine is preferentia lly incorporated into the apical site of CuO4F2 octahedra in Sr2CuO2F2+x. W e suggest that this work can provide an excellent basis for the application of XAS to investigate the electronic and crystal structures of copper oxyh alides. (C) 1999 Published by Elsevier Science B.V. All rights reserved.