Spherical YAG∶Ce^(3+) Phosphor Particles Prepared by Spray Pyrolysis

Spherical YAG：Ce^3＋ phosphor particles with narrow size distribution were prepared by spray pyrolysis. The effects of the concentration of solution, the flow rate of cartier gas and the annexing temperature on the phosphor morphology were studied. The productivity of precursor particles shows a trend of drop after rising with the increase of concentration Raising the flow rate of nitrogen can improve the productivity of the precursor particles. Phosphor prepared by spray pyrolysis has obviously higher emission intensity than that synthesized by solid state reaction, spray pyrolysis makes Ce^3＋ ions well distributed in the crystal lattice as the luminescent centers, and phosphor particles have regular sphericity and narrow size distribution.

Tricolor emitting and energy transfer in the phosphor Ba_2ZnSi_2O_7:Ce^(3+),Eu^(3+),Eu^(2+) for white-LED based near-UV chips

The red, green and blue （R/G/B） tricolor emitting phosphors Ba2ZnSi2O7 co-doped with Ce3＋and Eu3＋were synthesized in air atmosphere by a conventional high temperature solid-state reaction technique. All of the excitation spectrum of the phosphor Ba2ZnSi2O7：Ce,Eu showed a strong broad band absorption in the n-UV region whenever monitored by red （630 nm）-emitting or by green （500 nm）-and blue （402 nm）-emitting. Under the excitation of 330 nm, the emission spectrum containing a blue-violet emis-sion band, a green emission and four sharp lines originated from the characteristic transitions of Ce3＋, Eu2＋and Eu3＋ions, of which the relative intensities of the three emission bands could be controlled by the doping concentration of Ce3＋. The ca. CIE chromaticity co-ordinates （x=0.317, y=0.309） of the phosphor Ba1.94ZnSi2O7：0.03Eu,0.01Ce was very close to the standard white （x=0.33, y=0.33）, which suggested that it was a novel single-phased white-light emitting phosphor for LED-based near-UV chip. The mechanisms of energy transfer from Eu2＋to Eu3＋via Ce3＋was also discussed.

Hydrothermal synthesis and photoluminescent properties of Li_2Sr_(0.996)SiO_4:Pr_(0.004)^(3+) phosphors for white-LED lightings

Red phosphors, Li2Sr0.996 Si O4： Pr3＋0.004, with different hydrothermal conditions were prepared via hydrothermal synthesis and then heat-treatment. The chemical structures of the phosphors were identified with X-ray diffraction（XRD）. Surface morphological features were observed by scanning electron microscopic（SEM） investigation. Spectra of excitation and emission for the phosphors were also obtained by a spectrophotometer. Results showed that the optimum conditions were as follows： p H value of solution was 1–2, reaction temperature was at 180 oC for 24 h. The as-prepared phosphors exhibited two excitation dominant peaks at 451 and 486 nm, attributed to transitions of 3H4→3P2 and 3H4→3P0 of Pr3＋, respectively. A narrow emission peak at 610 nm corresponded to the energy level transition of 3P0→3H6 of Pr3＋ under excitation of light at 451 nm, which indicated promising candidate red phosphors for blue LED chips.