Bismuth silicate glass as host media for some selected rare-earth ions and effects of gamma irradiation

Ultraviolet, visible and infrared spectral measurements were used to investigate prepared undoped and rare-earth doped (2.5%) bismuth silicate glasses (80% Bi2O3-20%SiO2) before and after being subjected to gamma irradiation (8Mrad). The base bismuth silicate glass reveals strong extended UV-near visible absorption bands which are attributed to the presence of trace iron impurities in the raw materials together with absorption due to sharing of Bi3+ ions. The RE-doped samples show the same strong UV-near visible bands as the undoped glasses beside extra narrow characteristic bands mostly in the visible and near-infrared regions due to the respective studied rare-earth ions. The base undoped and all RE-doped samples except CeO2 sample reveal quite resistance to the effect of gamma irradiation due to heavy atomic mass Bi3+ ions present in high content (80%) and the rare-earth ions are known to be weakly affected due to the known 5s, 5p shielding. The exceptional effect of CeO2-doped sample is related to the ability of Ce3+ ions to change its oxidation state through photochemical reaction by irradiation or exchange with Fe3+ present as trace iron impurities. The FT infrared spectra of the prepared glasses reveal characteristic absorption bands which are related to the silicate groups together with the sharing of vibrational modes due to Bi-O groups. The IR spectra are slightly affected by gamma irradiation indicating the stability of the structural network groups consisting of SiO4 and BiO6 units.