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SnO2 nanocrystals with an average partiaxsxddccle size around 50 nm were prepared by using hydrothermal method. X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) data show that the doping of Eu3+ with concentrations ranging from 0 to 2 mol% resulted in a slight decrease of size from 50 to 35 nm. The High Resolution Transmittance Electron Microscopy (HRTEM) results of 1 mol% doping sample provide that the crystals size is around 38 nm and the interplanar spacing is 0.34 nm characterized for (110) planes of SnO2. Moreover, the peak shape and relative intensity of Eu3+ emission upon a direct and indirect excitation indicate the presence of two sites around Eu3+ ions, that are in the D2h sites of SnO2 and on the surface of nanocrystals. The Eu3+ ions located in different sites are selectivity excited. An optimizing of synthesis parameters can promote the incorporation of Eu3+ ions in SnO2 crystal lattice. Specially, the doping leads to the growth of crystallites along (101) preferred plane. The competition between red and orange emission as a function of Eu3+ contents was also considered. Under indirect excitation, the asymmetric ratio between 5D0-7F2 and 5D0-7F1 transitions of Eu3+ ions is unaltered at 0.3 in the range of Eu concentrations from 0.5 to 2 mol% achieved for the first time. PL spectra and decay measurements give evidence about the strong energy transfer between SnO2 and Eu3+ ions.

We have used trivalent terbium to investigate the mechanism behind fluorescence enhancement by Al 3+ co-doping. Our results indicate that rare-earth (RE) ions cluster together in aluminum-rich regions of the glass, and behave as if they were dispersed uniformly throughout these regions when the ratio of Al to RE is ∼10 or greater. We also studied the effects of adding chemical drying agents to the precursor solution for the synthesis of sol–gel-derived silicate glasses. Such glasses can be treated at significantly higher annealing temperatures without degradation of optical quality, and have the density of melt glass. Fluorescence yield from doped RE ions improves markedly with the addition of the drying agents, and the denser glasses are not subject to rehydration.