β-irradiation effect in aluminoborosilicate glasses: The role of RE codoping (RE = Sm, Gd)

Abstract

The effect of Sm and Gd codoping on the structural modifications of β-irradiated aluminoborosilicate glasses has been studied by electron paramagnetic resonance (EPR) and Raman spectroscopy. The EPR spectra showed that the relative amount of Gd3+ ions occupying network former positions (Gd 3+[n.f.] ) follows a nonlinear behavior as a function of the Sm/Gd ratio. This suggests that codoping favors the occupation by Gd3+ ions of the network former positions rather than the modifier positions in aluminoborosilicate glasses. The appearance of a superhyperfine structure of EPR lines attributed to boron-oxygen hole centers (BOHC) with increasing Sm/Gd ratio was observed. This suggests that Gd3+ ions are diluted in the vicinity of the BOHC defects. The concentration of defects created by irradiation reveals a nonlinear dependence on Sm and Gd codoping for the lowest irradiation dose (105 Gy). Therefore, codoping also affects the defect creation processes at least at the lowest irradiation dose. Raman spectroscopy measurements suggest that the irradiation-induced structural changes vary nonlinearly with the Sm/Gd ratio. In fact, the shift of the Si-O-Si bending vibration modes reveals a clear minimum for samples containing equal amounts of Sm and Gd (1: 1) in the investigated glasses.