Rare Earth Doped Luminescent Properties Of Nano-oxides And Glass Study

The structure and luminescent properties of Y2O3: Eu3+with different co-dopants were studied and compared each" other. The luminescent properties, such as the location of charge transfer band (CT band), the fluorescent intensity and lifetime of 5D0-7F2, varied with co-dopants. It can be concluded that the variation depended on co-doping by modifying the size and crystallinity of nanoparticles. And the dependence was more strongly on the crystallinity than the particle size. The detail contents were discussed as follows:(1) The nanopowders of Y2O3: Eu3+with different co-dopants (Li+, Na+, K+, Mg2+, Sr2+, Ba2+, B3+ and Al3+) were prepared by glycine-nitrate solution combustion synthesis. The nanocrystalline Y2O3 were cubic in symmetry by x-ray powder diffraction pattern. The average particle sizes estimated by Scherrer's equation indicated that dopants could finely adjust the average particle size.(2) The excitation and emission spectra were measured. Compared to undoped particles, the charger transfer (CT) band exhibited blueshift in most of doped particles. For Li+-doped particles, the shift was 6 nm. The emission intensity varied strongly with co-dopants. Li+-, Na+-, K+- and Sr2+-doped powders had stronger brightness than undoped ones, B3+- and Ba2+-doped powders had no obvious intensity change, and Mg2+- and Al3+-doped powders had weaker brightness.(3) The high-resolution emission spectra were recorded under the 266 nm laser excitation. A broader band was appeared between 620 and 630 nm, which was attributed to amorphous phase. The results indicated that the co-dopants of Li+, Na+ and K+ could promote the crystallinity of samples. However, the co-doping of Mg2+ and Al3+ drastically causes the structure disorder.(4) The fluorescence decay curves of 5Do of samples were measured under the excitation of 266 nm laser. The lifetime of particles co-doped with Li+ and Na+ increased as compared to that of un-doped one. However, the lifetime decreased asco-doped with other dopants.In addition, we also studied that ultraviolet (UV) light-induced spectral change in Eu3+-doped aluminosilicate glass and red to blue up-conversion emission of Tm3+-, Yb3+-doped Y2O3 nanocrystals. The detail contents as follows:(1) UV light-induced spectral change in Eu3+ doped aluminosilicate glass was studied. It was observed that the CT band decreased after irradiation. The intensity at the .irradiated site decreased linearly with the power density of the irradiation light. This means that the light-induced change is a one-photon process. Irradiations at different wavelengths indicate that the spectral change is frequency-selective. The dark decay of the spectral change was also studied. Two recovery time constants were obtained by fitting. One is 2.5 hours and the other is longer. The light-induced change of CT band was attributed to local structure change surrounding Eu3+ ions. - .(2) The "spectra of-upconversion emission of Tm3+by Yb3+ sensitization in Y2O3 nanocrystals were investigated. The very intense blue upconversion luminescence was observed by naked eyes under 978 nm laser diode (LD) excitation. The relationship between the LD working current and intensity of red and blue upconversion luminescence was studied. The intensity of blue upconversion decreased with time as the irradiation of 978 nm LD.