Study of structural evolution in Ce- and Nd-doped aluminoborosilicate glasses under β-irradiation
Résumé
The structural changes in aluminoborosilicate glasses under β-irradiation as a function of rare earth oxide content and the dose have been studied using Electron Paramagnetic Resonance (EPR) and luminescence spectroscopies. The EPR measurements at helium temperature (4 K) showed that β-irradiation affects valence state of cerium ions. According to concentration and dose dependences, the line with g ~ 2.89 can be attributed to paramagnetic Ce3+ ions resulting from Ce4+ reduction under irradiation. The effect of CeO2 content leads to the modifications of the EPR signal of defects at helium and the change in the relative proportion of electron and hole defects with the increase of the cerium doping level at room temperature. We observed also a decrease of the defect concentration as a function of the Nd doping into these glass compositions but by two orders less than for Ce-doped samples. Exposure to irradiation induced the appearance of a non-resolved EPR band in the region of defects. We can assume that possible dipolar interaction between Nd3+ ion and hole can result in not typical EPR resonance shape of paramagnetic defects at g ~ 2. Moreover, estimation of the ratio between splitted components of the 4F3/2 – 4I9/2 transition depending on the irradiation dose showed that dose increase leads to increase of this ratio suggesting that the nearest environment of Nd ions is expected to be changed