Luminescence properties of the Eu-doped porous glass and spontaneous reduction of Eu3+ to Eu2+

The luminescent properties of Eu3+-doped porous glass were investigated and reduction of Eu3+ to Eu2+ was observed when the Eu3+-doped porous glasses were heat treated in air. The absorption, emission and excitation spectra of Eu3+-doped porous glasses were measured and the results significantly depended on the treating temperature. The integral intensity of Eu3+ and Eu2+ ions at different temperatures was also investigated to investigate this reduction process. Electron spin resonance (ESR) spectra of the samples were also measured, which also confirmed the reduction effect. A possible mechanism was discussed to explain this process.