| Abstract
| - New cerium-doped scintillator glasses, obtained via sol−gel, were studied and Ce3+ luminescence efficiency was investigated, as a function of rare earth concentration and glass thermal treatments. The influence of Ce clustering on glass optical properties was also addressed. The principal microstructural features governing Ce luminescence in silica glass have been evidenced.
- The radioluminescence (RL) properties of Ce-doped silica glasses prepared by sol−gel method wereinvestigated as a function of the dopant amount in a wide range of concentrations (Ce:Si molar ratiosfrom 1 × 10-5 to 5 × 10-2). The effects of xerogel densification temperature and of a postdensificationthermal treatment were also considered. In order to understand the microstructural features governingCe3+ luminescence efficiency, optical absorption measurements in the ultraviolet, visible, and infraredregions and time-resolved photoluminescence experiments were performed. The complex dependence ofRL intensity upon rare-earth (RE) concentration and thermal treatment was attributed to the role of OHvibrations as nonradiative recombination channels, as well as to the formation of RE aggregates in thesilica matrix. Specifically, the segregation of CeO2 nanoparticles, in which Ce4+ does not supply anyradiative emission, has been revealed by infrared absorption measurements, in agreement with previousRaman, transmission electron microscopy, and X-ray diffraction data. Moreover, an optical absorptionband, centered at 2.4 eV and whose intensity increases with the square of cerium concentration, wasobserved and tentatively assigned to an intervalence electron-transfer transition involving Ce3+−Ce4+dimers. Postdensification thermal treatments markedly reduce the intensity of this band and increase RLintensity. The relationship between the 2.4 eV band and the RL properties will be outlined. In particular,the increase in RL intensity will be discussed, mainly as a consequence of microscopic modificationsleading to an improvement of the charge-transfer efficiency toward emitting centers.
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