Sintering process of Eu doped luminescent glass prepared from porous glass

Eu doped high silica glass prepared by sintering porous glass exhibits blue luminescence with high quantum efficiency. In this work, we studied effects of sintering temperature on valance state of europium ion. To investigate a change of valance state of Eu, X-ray absorption near edge structure (XANES) spectroscopy measurements were carried out. Intensity of blue emission at around 430nm drastically increases when the sintering temperature is above 1000°C. From XANES spectra, it is found that almost all the Eu exist as Eu³⁺ in a samples sintered below 900°C, while more than 70% of Eu exist as Eu²⁺ in the sample sintered at 1050°C and 1100°C. The drastic change of oxidation state of europium ion between 900 and 1050°C is discussed in relation to the structural change probed by infrared (IR) spectroscopy.