A Comparison of Modifications Induced by Heat-Treatment and γ-Irradiation in Spectroscopic Properties of Silica-Gel Thin Film Doped with Nd2O3

S. Bahammam, S. Abd El All, F. M. Ezz-Eldin

Thin SiO2 silica-gel film doped with 1mol.% Nd3+ ions has been synthesized using tetraethyl-orthosilicate (TEOS) and neodymium nitrate as precursor sources of silica and neodymium oxides. The amorphous nature of gel glasses has been confirmed by XRD spectra. XRD investigation shows that both low (500oC) and high (1150oC) heat-treated samples to be amorphous indicating that the Nd ions are incorporated in the SiO2 network. Both temperature and γ-radiation-dependent spectroscopic properties of Nd3+ ions in silicate glass were studied. As the temperature increases, the optical absorption (O.A.) intensity of Nd2+ increases sharply. However transmission% (T%)  decreases sharply except at maximal temperature (1150oC) where it is completely increased. Optical absorption spectra (UV-vis) of the samples before and after γ- irradiation show generation of new broad band below 500 nm (390–458nm) along with dips in the spectrum at the location of main Nd3+ absorption lines at maximal heat-treatment temperature (1150oC). This is attributed to the generation of different types of defects in the glass matrix along with possibility of change in the valence state of Nd3+ to Nd2+. The behavior of both O.A. and T% spectra of the irradiated samples designates a strong dependence with gamma radiation doses, where the magnetic dipole transition 5D0→7F1 of the Nd3+ ions presents huge defects for irradiation doses up to 18 kGy. FTIR absorption spectra of these glasses are found to be dominated mainly by the characteristics silicate groups and water (OH) present in the glass network. The effects of temperature on IR absorption are observed in the form of bond breaking and possible re-arrangement of bonding. However, γ- irradiation produces minor effect on the IR spectra which can be related to the shielding behavior of the glass. The generation and bleaching of irradiated sol gel glass were found to permit the creation and reduction of the larger part of Nd3+ or Nd2+ ions respectively in the glass. This study also shows the usefulness of this sol-gel glass as yes or no dischargeable irradiation detector, due to the remarkable color change after irradiation, which persists for a long time (up to 20 days).