Application of Mossbauer spectroscopy to iron ions in lithium tellurite glasses

The local structure around iron atoms in four series of lithium tellurite glasses were studied by means of Mossbauer spectroscopy with ⁵⁷Co(Pd) and Fe foil as the γ-ray source and reference. All the spectra showed one symmetric doublet peak. Quadrupole splitting increased with increasing Fe₂O₃ content and ranged from 0.61 to 0.84 mm/s, whereas the isomer shift was almost independent of Fe₂O₃ content, ranging from 0.37 to 0.39 mm/s. Comparison of isomer shift and quadrupole splitting values with those of the relevant crystals showed that all the iron ions were trivalent and octahedrally coordinated. The increase in quadrupole splitting with Fe₂O₃ was attributed to an increase in the geometric distortion of the FeO₆ octahedra. Linear correlation between quadrupole splitting and glass transition temperature was tentatively interpreted in terms of the relaxation of the Te-O framework.