Iron-bearing silicate glasses at ambient conditions

The effect of silica and iron content (Fe(2)O(3) of 2, 5 and 10 mol%) on the change of both Mossbauer spectra and elastic properties, is evaluated for glasses in the systems SFC: SiO(2)-Fe(2)O(3)-CaO, SFN: SiO(2)-Fe(2)O(3)-Na(2)O and SFL: SiO(2)Fe(2)O(3)-Li(2)O. To the degree of resolution obtained by Mossbauer spectroscopy glasses are paramagnetic down to 7 K. For a given cation (Ca(2+), Na(+) or Li(+)) spectra of glasses are largely independent of the silica and iron content, suggesting that the local environment of iron is not affected by the degree of polymerization. However, elastic properties, available for SFL and SFN glasses, significantly depend on composition. Whereas an increase in the network modifier cation Na lowers shear moduli of SFN, all elastic moduli increase with increasing amount of Li and Fe in SFL glasses. This strong dependence of elastic properties on chemical composition on one hand, and the chemically independent Fe-O bond in SFN and SFL glasses on the other hand, suggests that in the range of compositions considered, single bond properties may not determine physical bulk properties. (C) 2000 Elsevier Science B.V. All rights reserved.