X-ray absorption near edge structure (XANES) investigation of MnOy-doped sodium metaphosphate glasses and crystalline reference materials

The comparison of X-ray absorption near edge structure (XANES) spectra of MnOy-doped sodium metaphosphate glasses with the spectra of crystalline manganese oxides clearly indicates that the majority of the manganese ions are Mn2+, although the intensive violet color of these glasses is typical for manganese(III) containing phosphates. This finding is confirmed by permanganometric titration showing a maximum Mn3+-content of about 3 mol%. A decrease in the white line intensity with increasing manganese concentration is observed for a series of three glasses which is related to an increasing percentage of 4-fold oxygen coordinated manganese ions.