Defect centers in X-irradiated alkali phosphate glasses: EPR studies

X-irradiated samples of P ₂O ₅A ₂WO ₄A ₂O (A = Li, Na) glasses were studied by electron paramagnetic resonance (EPR) at X-band (9.5 GHz). Modifications of the EPR spectra are observed following in situ the sample's temperature or after thermal annealing. The spectra analysis was carried out by computer simulations specifically adapted for glasses in which statistical distributions are introduced for some EPR parameters. Three signals were detected: a hyperfine structure (doublet) which was assigned to a PO ₄^2- center, and two anisotropic signals attributed to the peroxy radicals.