White Led With Yag: Ce < Sup > 3 + < / Sup > Phosphor Synthesis Optimization Research

In this paper, the development of white LED and phosphor for white LED were introduced.The development course, research status, preparation method and the emitting mechanism ofyellow YAG: Ce phosphors were reviewed simply in this paper. The structure,morphology,luminous performances and spectral properties of YAG:Ce synthesized by hightemperature solid-phase method at different preparation conditions and the influence of rare earthions doped on luminous performances of YAG: Ce phosphor were studied.The results showed: the YAG:Ce synthesized by high temperature solid-phase methodbelonged to the yttrium aluminum garnet crystal structure. Small amount of Ce introduced intothe mixture did not affect the crystal structure of YAG. The use of flux in the preparationprocedure would be able to promote the reactions rate of high temperature synthesis effectively,but the shape of the emission spectrum of YAG:Ce did not be changed. The phosphorssynthesized via adopting mixed flux in the preparation procedure had better luminousperformances than those synthesized via adopting only single flux. Among those, the phosphorssynthesized via adopting flux BLP: SBL=2:1had the best light-emitting performance.TheYAG:Ce luminescence materials with better afterlow performance could be obtained by solidstate reaction method when reduction temperature was1350℃andreduction time was4h. However,the excessively high temperature or long time would cause growth of the yellow YAG:Cephosphor powder’s granularity whenever at sinter or reduction precedure. Powder particle sizeand luminescent properties were affected by heating mode and the order of reduction and ballmilling, but heating mode less effect to light-emitting properties of powder.When dopantconcentration X in phosphors reaches0.03, emitting intensity of phosphors will be the highest.the phosphor was preparated by the above process conditions of sample, its the crystalpowder,excitaion and emission peak intensity were obviously better than commodity powder’s. Ifthe sample powder blended with other powder toghther were used as white LED light source, theluminescent properties index of white LED must be better than commodity powder system’s.YAG:Ce doped small amount of Ln³⁺(Ln³⁺in this article represents Gd³⁺、Pr³⁺、Tb³⁺、Lu³⁺)belonged to the YAG the yttrium aluminum garnet crystal structure. The introduce of smallamount of rare earth ion Ln³⁺wouldn’t changed the crystal structure of YAG:Ce phosphors, butwould cause the lattice distortion. Doping rare earth would cause the drop of phosphor’s relativeluminous brightness, but would improve the phosphor’s CIE. The research showed emission peakof the YAG doped Gd³⁺shift to long wavelength direction. Emission peak of phosphors dopedPr³⁺locate in613nm, and emerge a Pr³⁺emission peak corresponding to the characteristicstransition1D₂—³H₄of the Pr ion in the YAG:Ce emission spectrum. When Tb>0.3mol,The obviously “redshift” phenomenon had been investigated in the phosphor’s emission spectrum.Gd³⁺、Pr³⁺、Tb³⁺improved the colour developing index of the yellow YAG: Ce powder. Andemission peak of YAG: Ce³⁺phosphor doped Lu³⁺appeared "blue shift", which the colourdeveloping index didn’t obviously improved.According to the best technology obtained, the phosphor Y_2.15Al₅O₁₂: Ce0.03Gd_0.7Pr_0.02withthe color coordinates x=0.4868, y=0.5022had been prepared. If the sample powder blendedwith other powder together were used as white LED light source, the colour developing index ofwhite LED must be better than commodity powder system’s.