Preparation And Luminescent Properties Of Several Typical (Oxy)Nitride Phosphors For White Light-Emitting-Diodes

(Oxy)nitride phosphors, as a new class of luminescent materials for use in white LED, have received significant attention in recent years, due to their abundant emission colors, high conversion efficiency, high physical-chemical stability, as well as their low thermal quenching. However, compared with oxide phosphors, the study of (oxy)nitrides is at an early stage. In this paper, focus on the problems of the existing research on the nitride/oxynitride phosphors, the researches have been carried out in three aspects:1. Luminescence spectra have been tuned and improved by simultaneous equivalent substitution of Al or Ga for Si in the anion [Si2O2N2]2-layer of typical oxynitride CaSi2O2N2:Eu2+. And the mechanism of the spectra shift and the luminescence intensity increasing have been explored. It indicated that the anion substitution is the other choice to tune the emission color, shift their excitation and emission bands. In addition, the photoluminescence intensity or the intensity of the emission maximum could be strengthen by reducing the lattice mismatch between the activator ions and the replaced host crystal ions and increase the critical dopant concentration of Eu+.2. A novel remarkable red oxonitridosilicate phosphor Sr2SiNzO4-1.5z:Eu2+(0.7<z<1.2), was synthesized by solid state reaction in NH3-N2atmosphere at1400-1500℃using the starting materials SrCO3, a-Si3N4, SiO2and Eu2O3, which could be easy to get and is stable in the air. Sr2SiNzO4-1.5Z:Eu2+(0.7<z<1.2) crystallizes in an orthorhombic structure with the space group of Pmnb:ba-c (no.62), and cell parameter aa=5.67366(5) A, b=7.09777(4)A, c=9.75112(1) A. Sr2SiNzO4-1.5z:Eu2+(0.7<z<1.2) exhibited broad-band red emission centred at～620nm, FWHM≈95nm, under blue light irradiation with a high QE value of78.0%. The thermal stability of the Sr2SiNzO4-1.5z:Eu2+obtained is superior to that of YAG:Ce3+(PY3-46) commercial phosphor. The outstanding luminescent properties allow it to be an attractive red luminescent material for white LED.3. A viable method for the production of (oxy)nitride phosphors with fine and well-dispersed powders at relatively low temperatures under ambient atmospheric pressure have been developed during the synthesis and investigation of the BN-based (oxy)nitride phosphors.(1) The oxynitride phosphors, which is composed of BCNO: Al without rare earth ions, have been synthesized at low sintering temperature (700-900℃) under atmospheric pressure. The result indicates that these BCNO:Al phosphors can emit under excitation not only by UV but also blue light; the color emission can be easily tuned from the blue to the orange regions of the photoluminescence spectrum by manipulating both the composition ratios of the raw materials as well as the reaction conditions; and with high quantum efficiency, i.e.,74.7%.(2) Large quantities of h-BN nanoplates with hexagonal morphologies have been successfully prepared by a facile template-and catalyst-free two-step method, which was carried out at comparatively low-temperature and under normal pressure conditions. The synthesized nanoplates have diameters of300-500nm and the thickness is about30nm. This two-step facile route developed the methods for growing nanosize nitride phosphors with uniform size distribution at relatively low temperatures under ambient atmospheric pressure.