Thermally reversible γ-ray-induced redox reaction between substitutional iron and aluminum impurity centers in a silica glass

• Published in: Journal of materials research Vol. 16; no. 1; pp. 127 - 131
• Main Author: Debnath, Radhaballabh
• Format: Journal Article
• Language: English
• Published: New York, USA Cambridge University Press 01.01.2001
• ISSN: 0884-2914; 2044-5326
• DOI: 10.1557/JMR.2001.0022

The magnetic properties of the substitutional iron and aluminum impurity centers in a sintered Vycor silica glass were studied before and after 1.1–1.3 MeV γ irradiation. Observation of two overlapping spin resonances (g ∼ 4.20–4.28) in the spectra of both the irradiated and preirradiated glasses indicated the existence of two types of tetra coordinated substitutional iron centers of the [FeO4−/Na+]0 type. The intensity of these electron-paramagnetic resonance (EPR) signals decreased upon g irradiation of the glass with concomitant generation of aluminum hole center [AlO4]0, which was manifested by the occurrence of a new six-line EPR signal with g 4 2.009, while thermal annealing of these aluminum oxygen hole centers restores the intensity of the iron centers almost to their preirradiation level. This result suggests that if not the whole, a major fraction of the electrons released in the process of g-ray-induced hole trapping at the Al site are captured by the substitutional iron centers. The electron traps, thus formed, are quite stable and can be deactivated by thermal stimulation.