Mössbauer studies on some glasses and crystals in the Na2O---Fe2O3---SiO2 system

Mössbauer absorption measurements have been made at room temperature on ⁵⁷Fe in iron sodium silicate glasses containing 3–15 mol% Fe₂O₃ and various iron alkali silicate crystals in order to study the state of iron in these glasses. The spectra of all the glasses gave one doublet with a quadrupole splitting varying from 0.73–0.78 mm s⁻¹, while those of Na₂O · Fe₂O₃ · 4 SiO₂ and 5 Na₂O · Fe₂O₃ · 8 SiO₂ crystals showed much smaller quadrupole splitting, 0.28 mm s⁻¹ and 0.10 mm s⁻¹, respectively, and an asymmetrical doublet of much narrower linewidth. When sodium was replaced by other alkali metals of larger size, such as K and Cs, in MFeSi₂O₆ and MFeSi₃O₈ crystals, the quadrupole splitting became wider and approached to 0.73 mm s⁻¹. Such a variation was not observed for glasses. These results suggest that a larger number of non-identical sites exist in iron sodium silicate glasses than in the corresponding crystals.