Optical properties and structural evaluation of Li2O–Al2O3–SiO2–TiO2 glassy semiconductor containing passive agent CeO2

In the present work, the effect of CeO2 as the passive agent on glassy structure of Li2O–Al2O3–SiO2–TiO2 (LAST) material for production of a new amorphous semiconductor has been investigated. Optical properties and vibrational spectroscopy of the samples have been studied using UV–Vis and FTIR absorption spectra, respectively. Accordingly, structural variations of 0–1.5% CeO2:LAST glasses were evaluated by calculation of density, molar volume, Urbach band tailing, direct and indirect optical band gaps, Fermi energy level and metallization criterion. Eventually for the analysis of the variation of energy level in presence of passive agent CeO2, Licciardello's model for glassy semiconductors was utilized. Results of the investigation illustrates that while Ce3+ ions could be regarded as the color agents due to spin allowed f–f transition, Ce4+ ions might have a destructive influence on negative-U centers (color centers) of the glass and hence, reduce the recombination centers in the band gap of the glass.

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► CeO2 plays the network modification role in glassy structure of LAST.
► Direct and indirect band gaps are almost equivalent for LAST glass containing 1.5% CeO2.
► Passive agent CeO2 obviated negative-U centers, i.e. recombination centers of glass.