Reduction of Eu3+ to Eu2+ in Eu-doped high silica glass prepared in air atmosphere

Eu-doped and Eu/Al-codoped high silica glasses (HSGs) are prepared by infiltration and densification method. Absorption, photoluminescence and electron spin resonance (ESR) spectra of the Eu-doped high silica glasses (HSGs) are measured and the results indicate the reduction of Eu3+ to Eu2+ ions partly in Eu/Al-codoped HSGs. Energy transfer between Eu2+ ions and Eu3+ ions is observed and this transfer enhances the intensity of Eu3+ ions. The reduction mechanism is also discussed.