Formation of Eu2+ in SiO2-Al2O3 Glass During Thermal Treatment in Sol-Gel Process

概要

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Although the Eu ion in a glass matrix is most stable in its trivalent form Eu3+, we found that a distinct blue photoluminescence (PL) from Eu2+ in Eu-doped SiO2-Al2O3 glasses was obtained without any deoxidizing treatments after a conventional sol-gel process. The incorporation of Al in a correct proportion to the concentration of Eu is essential for stabilizing Eu2+ during thermal treatment in the process. In order to understand the effect of the thermal treatment, we combined the result of thermal analysis with that of PL as a function of heating temperature. The PL spectral change from the defect-originated emission to the blue emission due to Eu2+ occurred at the temperature between 400°C and 600°C. An exothermic peak was observed at 450°C using our differential scanning calorimeter. We concluded that the reduction of Eu3+ and the stabilization of the resultant Eu2+ in the glass network takes place at the temperature around 450°C.
2004-03-01