Coordination and RedOx ratio of iron in sodium‐silicate glasses

Abstract

Mössbauer and Electron paramagnetic resonance (EPR) spectroscopy studies of iron status in doped sodium-silicate glasses (100−x, mol%)Na2O(x, mol%)SiO2(y, wt.%) Fe2O3 (x=75; 81; y=0.05–13) were made as a function of glass matrix and total iron content.55Total iron content is expressed as Fe2O3 in the paper. Mössbauer spectroscopy identified three signals: Fe3+ doublet, Fe2+ doublet and Fe3+ broad hyperfine splitting (HFS) at room temperature dealing with slow relaxation effect of ferric ions. X-band EPR spectra exhibits resonance signals at g≈2.0, g≈4.3 and a shoulder in the region of g≈6.0. EPR spectra were simulated on the basis of rhombic spin-Hamiltonian with Zeeman and fine-structure terms. The nature of EPR absorption signals was interpreted as a combination of five types of Fe3+ complexes. Three of them were clustered ferric ions and two others were isolated paramagnetic ferric ions in distorted octahedral sites. The iron RedOx ratio (Fe2+/Fe3+) has been estimated from Mössbauer spectroscopy, while proportion of Fe3+ ions in adjacent sites (Fe3+isolated)/Fe3+clustered) has been obtained from Mössbauer spectra and simulated EPR spectra.