The magnetic properties of substitutional Fe and Al impurity centers in a sintered Vycor silica glass were studied before and after 1.1 to 1.3MeV γ-irradiation. The observation of 2 overlapping spin resonances (g = 4.20 to 4.28) in the spectra of both irradiated and non-irradiated glasses indicated the existence of 2 types of tetra-coordinated substitutional Fe centers of the [FeO4-/Na+]0 type. The intensity of these electron-paramagnetic resonance signals decreased upon irradiation; with the concomitant generation of Al hole centers, [AlO4]0. This was associated with the occurrence of a new 6-line electron paramagnetic resonance signal, with g = 2.009. Thermal annealing of these hole centers restored the intensity of the Fe centers; almost to their pre-irradiation level. This suggested that many, if not all, of the electrons which were released during radiation-induced hole-trapping at the Al site were captured by substitutional Fe centers. Such electron traps were quite stable, and could be deactivated by thermal stimulation.

Thermally Reversible γ-Ray Induced Redox Reaction between Substitutional Iron and Aluminium Impurity Centers in a Silica Glass. R.Debuath: Journal of Materials Research, 2001, 16[1], 127-31