Effects of the Heat Treatment on the Photoluminescence Properties for La1-XPrxVO4 Phosphor Prepared by a Hydrothermal Method

Abstract

A hydrothermal method had been employed firstly for the preparation of La1-xPrxVO4 (x=0—0.05) nano-crystal phosphors, and then they were annealed at 600 oC for 4 h. The x-ray diffraction profiles show that the La1-xPrxVO4 phosphors still keep the tetragonal structure. The SEM results show that phosphor particles were increased from 60 nm to 80 nm after annealing process, and the surface morphology gradually changed from reunion to uniform distribution. The excitation spectra show that an absorption band between 200 ~ 330 nm is due to the charge transfer from the oxygen ligands to the central vanadium atom inside the VO4 3- anionic group, and the Pr3+ ion 4f-5d characteristic transition is located between in the 440 ~ 500 nm and 580 ~ 620 nm region. By 315 nm excitation, the main emission band still retains the characteristics for Pr3+ ion-doped LaVO4 phosphor, belonging to the host luminescent, and the 1D2→3H4, 3P0→3H6 electron transition of the Pr3+ ion, respectively. As the Pr3+ ion concentration increases, the color tone changes from blue ( 0 mol% Pr3+ ion doping ) to white (for 0.2-1 mol% Pr3+ ion doping), to blueish (for 5 mol% Pr3+ ion doping). Therefore, the color of the emission for (Y1-xPrx)InGe2O7 phosphors can be tuned by adjusting the Pr3+ ion concentration, without doping other color centers in a single phased host lattice. When the Pr3+ ion concentration of x=0.005, it possesses the strongest emission behavior, and is located in the white light region with a CIE chromaticity coordinates of x=0.299, y=258.