Structure of β-irradiated glasses studied by X-ray absorption and Raman spectroscopies

The structural modifications induced by external β-irradiation have been investigated to simulate the ageing processes of nuclear glasses under irradiation. Six glasses in the CaO–Al2O3–SiO2 system, from 10 to 68 mol% of SiO2 content, were irradiated with electrons generated by a Van de Graaf accelerator. The structure of these glasses was studied using Raman and X-ray absorption spectroscopies at the Al K-edge. We observe that a band appears at 1557 cm−1 in the Raman spectra of irradiated glasses, which is assigned to molecular O2, and that the average Si–O–Si bond angle decreases. An increase of the polymerization of the network is also detected in the Raman spectra of irradiated samples, which corresponds to a shift of the 1100 cm−1 band towards higher frequencies. This change in network polymerization is confirmed by an increase in the intensity of the main resonance at 1565 eV in the X-ray absorption spectra at the Al K-edge.