UV-visible, infrared absorption spectra of undoped and TiO2-doped lead phosphate glasses and the effect of gamma irradiation

Undoped and TiO2-doped lead phosphate glasses were prepared. Ultraviolet (UV)-visible and Fourier transform-infrared (IR) absorption spectra of the prepared samples were measured before and after being subjected to doses of 30 and 60 kGy of gamma irradiation. The parent undoped lead phosphate glass reveals charge transfer UV absorption bands which are attributed to the presence of unavoidable iron impurities contaminated within the raw materials used for the preparation of the glasses and the sharing of divalent lead (Pb2+) ions. Experimental spectral data indicate that the doped titanium ions are involved in such glasses in two valences, namely the trivalent and tetravalent states. The predominant trivalent titanium (Ti3+) ions are characterized by its purple color and exhibiting two visible absorption bands at about 500-550 and 700-720 nm. The lesser tetravalent titanium (Ti4+) ions belong to the d(0) configuration and generally exhibit only an UV absorption band. Spectral data show that gamma irradiation causes noticeable changes in the undoped and TiO2-doped samples in the UV range while the effects are limited in the visible range. The observed changes in the UV region are attributed to photochemical reactions while TiO2-doped samples show retardation or shielding toward continuous gamma irradiation together with the sharing of heavy Pb2+ ions. IR absorption spectra reveal the vibrations of several phosphate groups including the metaphosphate chains as the main structural building units together with the possible Pb-O vibrations.