INTERPRETATION OF THE FE-57 MOSSBAUER-SPECTRA OF SOME PHOSPHATE-GLASSES

Fe-57 Mossbauer spectroscopy has been used to examine a number of phosphate glasses containing iron a as alpha-Fe2O3. Glasses melted for a long duration in air gave a Fe3+/Fe2+ ratio of 60140 whilst those melted in an inert atmosphere showed a total absence of Fe3+ and those melted for a short duration in air gave a 85/15 ratio. A quadrupole splitting distribution programme was used to fit the spectra in terms of ferric and ferrous iron envelopes. For the glass melted in air, this yielded Gaussian profiles indicative of octahedral sites for both Fe3+ and Fe2+. The Fe2+ profile of the glass melted in the inert atmosphere and the Fe3+ profile of the glasses melted for the short time were both resolved into two Gaussians. In each case, one was similar to that for the glass melted in air whilst the second represented more disordered iron sites. Two distinct types of iron site appear to be present in these glasses, one preferentially occupied by Fe3+ and the other by Fe2+. Adjustment of the Fe3+/Fe2+ ratio causes both types of site to be occupied by either Fe3+ or Fe2+.