Synthesis, Characterization And Luminescent Properties Of Phosphor For LED

It is well-known that white light emitting diode（WLED）is a novel semiconductor illumination lamp-house,which offer it a number of advantages compared to existing light source.However,the efficiency of phosphors for LED is still very low nowadays.Therefore,it’s an urgent task to enhance the efficiency of existing phosphors and develop new-type phosphor with high efficiency.Sr₂CeO₄ is a new kind of potential phosphor for LED,for its high luminous efficiency and chemical stability,which can be excitated by UV wavelength near 300 nm.However,the synthesis process of Sr₂CeO₄ needs to be improved for its industrialization,the excitation peak needs to be adjusted to the emission spectra of LED chip,as well.Sr₂MgSiO₅:RE,a kind of phosphor prepared by domestic researchers,is a new kind of phosphor for LED with high luminous efficiency,followed by the Y₃Al₅O₁₂∶Ce³⁺,with good chemical stability,which is suitable for the UV wavelength of LED chip.Although Sr₂MgSiO₅:RE meets the demands of LED,it’s necessary to improve the synthesis method,to increase the luminous efficiency,to make the further study for this new kind of material.In order to come ture the phosphor’s industrialized application in the field of LED successfully,the content of this paper are mostly involved in the improvement of Sr₂CeO₄ phosphor’s synthesis method,using rare earth ions as Sr-2CeO-4 phosphor’s dopant,and also involved in the improvement of Sr-2MgSiO₅:Ce³⁺phosphor’s synthesis method,the influence of host’s change,using the rare earth ions as this kind of phosphor’s dopant and investigating the luminescent property.In order to develop efficient lighting sources using high-brightness UV white LEDs,four researches of phosphors which generate white light excited by UV LEDs had been carried out in this thesis. 1.Optimization of methodology of Sr₂CeO₄ phosphorWith H₃BO₃ as flux,the crucial factors,which can affect the synthesis of Sr₂CeO₄ phosphor,was optimized by orthogonal test.The suitable amount of H₃BO₃ could facilitate luminous efficiency of Sr₂CeO₄.In some extent,when the molar ratio of n_sr/n_cedeviated from the unit ratio of Sr₂CeO₄ phosphor,the crystalline powders possess better structure,and the luminescent intensity were enhanced,as well optimized factors of Sr-2CeO-4 preparing by 1200℃for 3 hours,keeping the molar ratio of n_sr/n_ceat 5.5 and using 6.5%H₃BO₃ as flux.2.Synthesis,characterization and luminescent properties of Sr₂CeO₄:RE phosphorSr₂CeO₄ is also a kind of well host of luminescent phosphor.After doping lanthanon ions,Sr₂CeO₄:RE(RE=Eu³⁺,Dy³⁺)phosphor have been synthesized, the characterization and luminescent properties were investigated.It was found that the emission peak could shift from blue wavelength to red,green and yellow wavelength.The emission peak and luminous intensity could be adjusted by controlling the concentration of dopant.3.Soft synthesis and effect of solid solution of M_xM’_2-xMgSiO₅:Ce³⁺on luminescent propertiesSr₂MgSiO₅:Ce³⁺were prepared by sol-gel in lower temperature,less time than high temperature solid-state method.The luminous efficiency of samples prepared by sol-gel was enhanced greatly.The luminescent properties of Ce³⁺ ion was very easily affected by the field of crystalline.After changing host of M_xM’_2-xMgSiO₅ phosphor,the luminescent properties of M_xM’_2-xMgSiO₅: 0.03Ce³⁺have also varied with the host’s change.By controlling the component, the emission peak could shift from 410 nm to 445 nm.Basing on the study of Ca_1.5Sr_0.5MgSiO₅:Ce³⁺phosphor,it was found that Ca_1.5Sr_0.5MgSiO₅ could be used as a good host for luminescence materials,with the better luminescent properties than Sr₂MgSiO₅:Ce³⁺phosphor.4.Luminescent properties of Ca_1.5Sr_0.5MgSiO₅ doped with Dy³⁺,Eu³⁺/Eu²⁺, Pr³⁺and Sm³⁺Ca₁₀₅Sr_0.5MgSiO₅ phosphor doped with Dy³⁺,Eu³⁺/Eu²⁺,Pr³⁺and Sm³⁺were prepared by high temperature solid-state method,respectively.The luminescent properties of phosphors have been investigated in detail.It was found that Ca_1.5Sr_0.5MgSiO₅ could convert from UV wavelength to visible light.Some of the phosphor have shown potential application value in LED.