Optical properties and structural evaluation of Li2O-Al2O3-SiO2-TiO2 glassy semiconductor containing passive agent...

In the present work, the effect of CeO(2) as the passive agent on glassy structure of Li(2)O-Al(2)O(3)-SiO(2)-TiO(2) (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% CeO(2):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 CeO(2), Licciardello's model for glassy semiconductors was utilized. Results of the investigation illustrates that while Ce(3+) ions could be regarded as the color agents due to spin allowed f-f transition, Ce(4+) 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.