Effects of thermal treatments in controlled atmosphere on the Ce oxidation state in Ce–Ti-Eu doped SiO2 sol–gel glasses

Quantitative UV–VIS spectroscopic studies of photo-thermo-refractive glasses. II. Manifestations of Ce3+ and Ce(IV) valence states in the UV absorption spectrum of cerium-doped photo-thermo-refractive matrix glasses

“…This explains a substantial predomination of the Ce(IV)-related absorption in the spectra of all Ce-containing glasses except those synthesized in the reduction conditions. Data by Agnello et al [16] on Ce\Ti\Eu-doped SiO 2 glasses indicated the shifts of the Ce 3+ ⇆ Ce(IV) equilibrium under the effects of mildly reducing and strongly oxidizing atmospheres (He and O 2, respectively ), which is in accord with our results. As to conclusions by Agnello et al on changes in the structures of sites occupied by the Ce 3+ and Ce(IV) valence states under the effect of heat treatment of these glasses, no direct comparison of the conclusions with our results can be conducted due to reasons as follows.…”

“…Judging by data for Samples 1-3 and 5, the total molar absorptivity μ total CeIV of the strongest Ce(IV)-related oscillator exceeds the total molar absorptivity μ total Ce3 + of the strongest Ce 3+ -related oscillator by approx. 16 times. This explains a substantial predomination of the Ce(IV)-related absorption in the spectra of all Ce-containing glasses except those synthesized in the reduction conditions.…”

“…When studying Ce\Ti\Eu-doped SiO 2 glasses, Agnello et al [16] have shown recently that the heat treatment of samples at 390°C in the He and O 2 atmospheres affects their optical absorption, photoluminescence and Raman spectra. Reasons for affecting were assumed to be not only shifts in the redox equilibria but also thermally induced changes in the structures of sites occupied by the Ce 3+ and Ce(IV) valence states.…”