The Preparation Of Yag Yellow Phosphor For White Led

The white light emitting diode (WLED) as the new generation of light source, has the unique advantages of high luminous efficiency, energy saving, green and non-pollution. It is quite potential and attractive to the world because of energy sources crisis and the environment is getting worse. Most white LED in the commercial market is phosphor-converted LED, which is realized by coating YAG phosphors on the blue LED chip.The YAG phosphors emit yellow light excited by the blue light, and the two lights mix into the white light.So the synthesis of YAG phosphor with better properties isquite important in the researches nowadays.In this dissertation, YAG phosphor is synthesized by the advanced Pechini method and solid-state method. DSC-TG, XRD, SEM, luminescent (PL) spectral are used to characterize the phosphors prepared by the two methods.In the advanced Pechini method, the effects made by the ways of drying the gel, the presintering temperature, the time and the temperature of calcining, and different Ce concentration are investigated by a lot of experiments. The results showed that:the precursor calcined at860℃can form the pure YAG crystalline phase. We can get the particles with great shape and high luminous efficiency after drying at500℃, pre-calcining at1200℃, and calcining at1500℃.Ce, as an activator, its concentration affects a lot to the luminous efficiency directly. In the analysis of the luminescent (PL) spectral with different Ce concentration, the result showed that the luminous efficiency reached to its maximum at x=0.06(Y3-xCexAl5O12).In the solid-state method, the temperature and time of calcining, the addition of different fluxes and the concentration of Gd doped YAG phosphor are investigated to find out their effects to the YAG phosphor. The results showed that rising the temperature of calcining is benefit to the luminous intensity. And take the second calcinations after grinding the YAG phosphor calcined for the first time can effectively improve the luminous efficiency. The addition of flux can reduce the temperature of the conversion of YAG crystalline phase and benefit to its luminous intensity. The emission spectra moved from541nm to566.1nm when the concentration of Gd increased from0to0.9(Y3-0.06-xGdxCe0.06Al5O12), but the luminescent intensity has decreased.After coating the YAG phosphor on the blue LED chip, the results showed that the luminous efficiency of YAG phosphor synthesized by advanced Pechini method is82.371m/W, and the luminous efficiency of YAG phosphor synthesized by solid-state method is81.31m/W, they are both so closed to the current standard of commercial YAG phosphor. The Gd doped YAG phosphor has decreased its luminous efficiency, but the color rendering index can reach to80.