Coordination and RedOx ratio of iron in sodium-silicate glasses

Mossbauer 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.(5) Mossbauer 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 approximate to 2.0, g approximate to 4.3 and a shoulder in the region of g approximate to 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 Mossbauer spectroscopy, while proportion of Fe3+ ions in adjacent sites (Fe-isolated(3+))/Fe-clustered(3+)) has been obtained from Mossbauer spectra and simulated EPR spectra. (C) 2012 Elsevier B.V. All rights reserved.