Effects of local atomic order on the pre-edge structure in theTiKx-ray absorption spectra of perovskiteCaTi1−xZrxO3

Abstract

The effects of local B-cation (Ti, Zr) distribution and octahedral tilting on the pre-edge structure in the Ti x-ray absorption $K$-spectra of the ${\mathrm{CaTi}}_{1-x}{\mathrm{Zr}}_x{\mathrm{O}}_3$ perovskite solid solutions were investigated. Experimental spectra for the disordered ${\mathrm{CaTi}}_{1-x}{\mathrm{Zr}}_x{\mathrm{O}}_3$ samples revealed systematic variations of the pre-edge peak intensities with the $x$ values. Multiple-scattering calculations using 75-atom clusters $\mathrm{Ti}\left({\mathrm{TiO}}_6{)}_{6-\mathrm{n}}\right({\mathrm{ZrO}}_6{)}_{\mathrm{n}}{\mathrm{Ca}}_8{\mathrm{O}}_{24}$ were conducted to interpret these differences. The origin of the lowest unoccupied states in the conduction band of the ${\mathrm{CaTi}}_{1-x}{\mathrm{Zr}}_x{\mathrm{O}}_3$ was determined from the analyses of x-ray absorption near-edge structure of the O $K$-edge. The calculations reproduced the experimental spectra and demonstrated that the differences in the intensities of certain pre-edge feature are dominated by the probability of finding a Zr atom in the first B-cation coordination sphere around the absorbing Ti. The pre-edge structure appeared to be sensitive to small changes in the value of this probability, so that the pre-edge intensities could be used effectively to compare the extent of local B-site order in perovskite solid solution samples having similar chemical composition but processed differently.