Vibrational spectroscopy of OH-related groups in Ce3+- and Gd3+-doped silicate glasses

FTIR spectroscopy was applied in the 500–14,000 cm−1 range to detect OH vibrational modes (stretching, bending, combination, first and second overtone) in Ce3+- and Gd3+-doped silicate glasses, prepared by means of the sol–gel technique and aimed to applications as scintillators. The presence of OH groups, belonging either to silanol (Si-OH) or to H2O should be limited, since they could cause radiative emission quenching. The samples, doped with Ce3+ or Gd3+ (0.05–3% m.f.), were submitted to thermal treatments at 450°C, 750°C, and 1050°C, to remove water and organic groups for producing a dense glass. A large amount of H2O and Si-OH is still present in samples annealed at 450°C and 750°C, while only a reduced quantity of Si-OH (evaluated as <1% m.f.) is detected after annealing at 1050°C, i.e. in the final dense glasses (for all concentrations of both dopants).