  Two series of Sm-, Gd-codoped aluminoborosilicate glasses with different
total rare earth content have been studied in order to examine the codoping
effect on the structural modifications of beta-irradiated glasses. The data
obtained by Electron Paramagnetic Resonance spectroscopy indicated that
relative amount of Gd3+ ions located in network former position reveals
non-linear dependence on Sm/Gd ratio. Besides, codoping leads to the evolution
of the EPR signal attributed to defects created by irradiation: superhyperfine
structure of boron oxygen hole centres EPR line becomes less noticeable and
resolved with increase of Gd amount. This fact manifests that Gd3+ ions are
mainly diluted in vicinity of the boron network. By Raman spectroscopy, we
showed that the structural changes induced by the irradiation also reveal
non-linear behaviour with Sm/Gd ratio. In fact, the shift of the Si-O-Si
bending vibration modes has a clear minimum for the samples containing equal
amount of Sm and Gd (50:50) in both series of the investigated glasses. In
contrast, for single doped glass there is no influence of dopant's content on
Si-O-Si shift (in case of Gd) or its diminution (in case of Sm) occurs which is
explained by the reduction process influence. At the same time, no noticeable
effect of codoping on Sm3+ intensity as well as on Sm2+ emission or on Sm
reduction process was observed.
