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

We report an experimental study by optical absorption, photoluminescence and Raman spectroscopies of the modifications induced on Ce–Ti-Eu doped SiO2 glasses by thermal treatments in controlled atmosphere. Samples with Ce content varying up to 5,000 part per million by weight (ppm) and with Ti and Eu content fixed at 40 and 300 ppm respectively, have been investigated. The treatments were done in inert atmosphere of He and in O2 atmosphere at 390 C and 100 bar. Our experiments show that only Ce4? ions are affected by He treatments, whereas both Ce4? and Ce3? ions are affected by O2 treatments. The obtained results are interpreted on the basis of microstructural changes induced by the thermal treatments on Ce sites and by the occurrence of an oxidizing process.