Preparation And Luminescence Properties Of Phosphors Excited By Ultraviolet

White light emitting diodes (WLED) have been considered to be new generation light sources due to their advantages such as energy saving, environmental protection and long life time, and it will have a wide market and good prospect of development. For white LED sources, the most promising devices are phosphor-coated LEDs. There are two kinds of approaches to get white LEDs:(a) blue LEDs with yellow phosphors and (b) UV LEDs with tricolor phosphors. The purpose of this project is to search for new efficient trichroamtic phosphors which can be excited effectively by ultraviolet LED chips.In this paper, trichromatic phosphor (Red Green Blue) and single matrix white light emitting phosphor have been synthesized. Their phase composition, structure and luminescence properties were carefully investigated.(1) K2Ca1-xSi04:xEu3+phosphors were successfully synthesized by solid-state reaction method. The result showed the main emission peaks of Eu3+ion are located at591nm and617nm, attributed to the transition5Doâ†'7F1and5Doâ†'7F2respectively; The maximum intensity of luminescence was observed at Eu3+concentration around7mol%. The quadrupole-quadrupole interaction between Eu3+ions is the dominant mechanism for concentration quenching of fluorescence emission; The thermal activation energies (0.872eV) for K2Ca0.93Si04:0.07Eu3+were obtained from the temperature dependent (303K-463K) luminescence intensities. So it call be used as the red compensating phosphor in "blue+yellow" model and the red phosphor in the system of tricolor phosphors by UV-LED based.(2) Sr2-x-yB5O9Cl:xEu2+,yTb3+blue phosphors were successfully synthesized. The crystal structure was carefully analyzed by X-ray diffraction (XRD). The factors of Eu2+/Tb3+concentration, excess of flux H3BO3and reaction temperature affected the PL intensity of Sr2B5O9Cl phosphors have been investigated by Hitachi F-7000fluorescence spectrometer. The result showed that concentration quenching mechanism is electric dipole-electric dipole interaction mechanism and concentration quenching Critical distance is calculated to be about Rc=1.71nm in single-doped Eu2+phosphor. Furthermost, a strong absorption in the region of230-410nm, it is a potential blue emission phosphors for near-ultraviolet white LED.(3) Sr1-x-yMgP2O7:xCe+,yTb3+phosphors were successfully synthesized by solid-state reaction method. The crystal structure, optical properties, energy transfer and thermal stabilities were carefully investigated. The result showed that the emission peaks of Ce3+ion and Tb3+ion are located at398nm and545nm in the SrMgP2O7host, attributed to the transition d-f and5D4â†'F5respectively. The Co-doped Ce3+/Tb3+, an efficient energy transfer from Ce3+to Tb3+ions by means of dipole-dipole interactions and the critical distance of the energy transfer is about0.614nm. The activation energyâ–³Eis calculated about0.122eV for Ce3+and0.111eV for Tb3+by single-doped Ce3+or Tb3+(4) The NaBaPO4:Eu2+,Mn2+phosphors were synthesized by the solid-state reaction method. The crystal structure, photoluminescence emission and excitation spectra and decay times of the phosphors were carefully investigated. The results revealed that these phosphors show two emission bands peaking at around435nm and555nm, the energy transfer from Eu2+to Mn2+ions by dipole-dipole interaction and the critical distance of the energy transfer is calculated to be about0.589nm. Moreover, varying the relative concentration of Mn2+, the CIE coordinates shift from (0.1663,0.0838) to (0.2308,0.2173).