Oxidation state characterization in Cr oxides by means of Cr Kb emission spectroscopy

Abstract

High resolution Kb spectra of Cr oxide were measured using a non-conventional spectrometer. Theoretical spectra were obtained using the DV-Xa method in order to interpret the Kb spectrum structures. Kb spectrum structures were analyzed and spectral parameters show a great sensitivity to the oxidation state and to the Cr-O distance. Purity samples of CrO2 were obtained by means of thermal treatment at 513 ºC under oxygen pressure of 200 bar. X-ray diffraction patterns show a typical rutile structure, without spurious phases. The CrO2 data allowed to confirm the linear dependency of the Kb1,3 and Kb5 energy positions with the oxidation state. The energy of the Kb2,5 line relative to the Kb1,3 line seems to be a suitable parameter for characterization of the oxidation state. The relative Kb´´ transition probability per Cr-O falls exponentially with Cr-O increasing distance. This behaviour was not found in the literature for Cr oxides.