Titanium reduction processes in oxide glasses under electronic irradiation

Borosilicate and disilicate glasses doped with 0-2 mol% of TiO2 have been irradiated with 2 MeV electrons. Reduction of Ti4+ is attested by the presence of an intense electronic paramagnetic resonance (EPR) signal around g = 1.92 corresponding to Ti3+, not observed in samples that were not irradiated. Moreover, two distinct sites of Ti3+ have been detected in each glass composition. Ti-K-edge X-ray absorption near edge structure (XANES) experiment and more precisely the pre-edge analysis of non-irradiated samples indicates the presence of four, five and six coordinated Ti(IV) in borosilicate glass compositions. In contrast, the average Ti(IV) coordination in DS composition is a mixture between fivefold and sixfold. In irradiated glasses, the Ti-K-edge energy (as well as the pre-edge position) shows a shift to smaller energies, which we suggest is caused by Ti3+. Comparison between EPR, Raman and XANES results in a coherent description of Ti4+ reduction process in the glass samples. (C) 2007 Elsevier B.V. All rights reserved.