X-ray absorption and photoemission electron spectroscopic investigation of crystalline and amorphous barium silicates

X-ray absorption near edge structure (XANES) measurements at the Si K-edge, X-ray photoelectron spectroscopy of the Si 2p and O 1s photoelectrons and X-ray excited Auger electron spectroscopy of the Si KLL Auger electrons are applied in order to investigate the degree of polymerisation (Qn) of the (SiO4)-polyhedra in barium silicate glasses with different BaO-contents. The spectra of the glasses with 33.3 and 37.0 mol% BaO are compared to those of the crystalline reference compounds: low quartz, BaSi2O5, BaSiO3 and Ba2SiO4. The analysis reveals a high average polymerisation between Q3 and Q4 in both glasses. The results are supported by calculations of the bound state transitions in Si K-XANES using the multiple scattering Xα method.