Nanocrystalline Eu3+-doped CeO2, CeO2, Sm3+-doped CeO2, and Li+, Eu3+-codoped CeO2 samples were prepared through a sol−gel process. The structure and the optical properties of the samples were characterized by X-ray diffraction, diffuse reflection spectra, and photoluminescence spectra. No luminescence was observed for nanocrystalline CeO2. The systematic investigation shows that the broad band in the excitation spectrum of CeO2:Eu3+ comes from the charge transfer (CT) transition from O2− to Ce4+, not from the oxygen vacancy, or from the CT of O2− to Eu3+. Upon increasing the fired temperature from 600 to 800 °C, the excitation spectrum shifts to lower energy. With increasing concentrations of Eu3+ up to 1% in CeO2, red shifts of the excitation spectra are observed; however, when the concentration of Eu3+ increases to 5% and 10%, blue shifts occur. The emission spectrum shows that the symmetry of the Eu3+ site becomes lower with increasing Eu3+. Based on the dielectric theory of complex crystals, the environmental factor (h e) and the dielectric definition of average energy gap around the centers of Eu3+ are calculated. The reasons for the shifts of the excitation spectra are discussed in detail.

Y 2 O 3 : Eu 3+ and Li-doped Y2O3:Eu3+ luminescent thin films have been grown on sapphire substrates using pulsed-laser deposition. The films grown under different deposition conditions have been characterized using microstructural and luminescent measurements. The photoluminescence (PL) brightness data obtained from Li-doped Y2O3:Eu3+ films grown under optimized conditions have indicated that sapphire is a promising substrate for the growth of high-quality Li-doped Y2O3:Eu3+ thin-film red phosphor. In particular, the incorporation of Li+ ions into Y2O3 lattice could induce a remarkable increase of PL. The highest emission intensity was observed with LiF-doped Y1.84Li0.08Eu0.08O3, whose brightness was increased by a factor of 2.7 in comparison with that of Y2O3:Eu3+ films. This phosphor may promise for application to the flat panel displays.

Y2O3:Eu3+ and Li-doped Y2O3:Eu3+ luminescent thin films have been grown on sapphire substrates using a pulsed laser deposition technique. The thin-film phosphors were deposited at a substrate temperature of 600°C under the oxygen pressures of 100, 200, and 300 mTorr. The films grown under different deposition conditions have been characterized using microstructural and luminescence measurements. The crystallinity and photoluminescence (PL) of the films are highly dependent on the oxygen pressure. The PL brightness data obtained from Y2O3:Eu3+ films grown under optimized conditions have indicated that sapphire is a promising substrate for the growth of high-quality Y2O3:Eu3+ thin-film red phosphor. In particular, the incorporation of Li+ ions into Y2O3 lattice could induce a remarkable increase of PL. The highest emission intensity was observed with LiF-doped Y1.84Li0.08Eu0.08O3 (Y2O3LiEu), whose brightness was increased by a factor of 2.7 in comparison with that of Y2O3:Eu3+ films. This phosphor may hold promise for application in flat-panel displays.