Local order around tungsten atoms in tungstate fluorophosphate glasses by X-ray absorption spectroscopy

X-ray absorption spectroscopy was used to study the local environment of tungsten atoms in NaPO3–BaF2–WO3 glasses and the results were compared with crystalline references Na2WO4 and WO3. XANES measurements at the W-L1 edge allowed to determine a distorted octahedral environment of tungsten atoms in these glasses similar to the local order of tungsten in monoclinic WO3. Extended X-ray absorption fine structure (EXAFS) has been used as a local probe to monitor the effect of WO3 concentration on the tungsten environment. Based on an analysis of the EXAFS data, we proposed a three-shell model of oxygen atoms around tungsten as in monoclinic WO3. With increasing WO3 concentration, it was found that R2 decreases from 1.96 to 1.92 Å whereas R3 increases from 2.07 to 2.12 Å.