LiYF_4 nanocrystals with tetragonal structure were adopted as the host materials for the phosphors and scintillators owing to the low phonon energy and high optical transparency. LiYF_4：Ln^（3＋）（Ce^（3＋）,Eu^（3＋）） nanocrystals were fabricated by solvothermal method. Under UV excitation, they could emit visible light. In order to improve the luminescence intensity, the method of co-doping LiYF_4 nanocrystals with Sc was adopted. Sc^（3＋） ions could reduce the lattice expansion caused by the doping of Ce^（3＋） or Eu^（3＋） whose ionic radius was larger than Y^（3＋）. Crystal structure of Li（Y,Sc）F_4：Ln^（3＋） kept much more stable and the luminescence intensity could be significantly enhanced when the concentration of Sc was a moderate value. Thermoluminescence was employed to analyze the electron traps in Li（Y,Sc）F_4：Ce^（3＋）. Results suggested that the suppression of the generation of electron traps with the co-doping of Sc contributed to the enhancement of luminescence intensity of LiYF_4：Ce^（3＋）.
Single crystal of Lu2Si2OT：Pr was grown by Czochralski method. Transmittance, photoluminescence excitation （PLE） and photo- luminescence （PL） spectra, X-ray excited luminescence （XEL） and fluorescence decay time spectra of the sample were measured and dis- cussed to investigate its optical characteristics. The crystal structure of the as grown Lu2Si207：Pr was confirmed to be C2/m. There was a broad absorption peaking at 245 um in the region from 200-260 urn. The PL spectntm was dominated by fast 3py^3Hj band peaking at 524 nm. The XEL spectrum was dominated by the fast 5d14t^---~41e emission peaking at 265 nm. The 2D （temperature-intensity） and 3D （tem- perature-wavelength-intensity） thermally stimulated luminescence （TSL） spectra were measured. The Pr3＋ ion was found to be the recombina- tion center during the TSL process. Three obvious traps were detected in LPS：Pr single crystal with energy depth at 1.06, 0.78 and 0.67 eV.
