ESR spectroscopy of FeIII ions in sodium silicate glasses

The state of Fe^III ions doped in sodium silicate glasses of the composition (100 ? x)Na₂O-xSiO_2?y Fe₂O₃ (x = 75, 81 mol.%; y = 0.05?13 wt.%) was studied by electron spin resonance (ESR). X-band ESR spectra exhibited three resonance signals at g ≈ 2.0, 4.3, and 6. The computer simulation of ESR spectra was performed on the basis of spin-Hamiltonian of rhombic symmetry. The nature of observed signals was interpreted as a combination of five types of Fe^III complexes. Three of them were clustered iron ions and two other were isolated paramagnetic ones. The ratio of observed forms was found for different glass compositions and various total amounts of Fe^III ions in a matrix containing 0.55, 2.5, 4, 7, and 13 wt.% of Fe₂O₃.