Deconvolution analysis of Ga K-edge XANES for quantification of gallium coordinations in oxide environments

A quantitative analysis of gallium species (GaO4 tetrahedra and GaO6 octahe dra) by means of X-ray absorption spectroscopy (XANES and EXAFS) at the Ga K-edge was performed on a series of gallium oxides with various phases and SiO2-supported ones. XANES spectra of gallium oxides showed two distinguish able peaks that were assigned to tetrahedral and octahedral gallium oxide s pecies on the basis of a comparison with those of reference compounds. A de convolution analysis of XANES spectra was carried out on the assumption tha t the absorption due to each species is expressed by a set of Gaussian and arctangent functions, and the tetrahedral/octahedral ratios were quantitati vely estimated from the ratio of the peak areas. By the EXAFS curve-fitting analysis, the tetrahedral/octahedral ratios were also estimated, and they were in good agreement with those obtained by XANES analysis. It was conclu ded that the Ga atoms with a different coordination symmetry (tetrahedral o r octahedral) can be estimated quantitatively by a deconvolution analysis o f XANES.