The Preparation And Luminescence Properties Of A White Light-emitting Diodes Used Phosphor Sr_3-yEu_ySiO_5-6xN_4x

In the past decades, an overwhelming evolution of white light-emitting diodes（WLEDs） had swept all over the world. The phosphors which play an important rolein WLEDs generating white light are drawing more and more attention. Owning to thehigh chemical stability and high luminous efficiency under blue or ultraviolet light,the silicate phosphors become new promising phosphors that has been used inWLEDs, especially （Sr, Ba）₃SiO₅:Eu²⁺, whose emission spectrum is closer to the redarea than that of YAG: Ce³⁺. This character can ameliorate the drawbacks, such as lowcolor rendering index and high color temperature, caused by the deficiency of redcomponent of traditional “YAG+Blue chip” type WLEDs.An orange-red emitting phosphor (Sr_1-xBa_x)_3-yEu_ySiO₅was synthesized bysolid-state reaction in a reducing atmosphere and characterized by X-ray diffraction（XRD） and fluorescence spectrophotometer. The results indicate that the synthesizedphosphors are isostructural with Sr₃SiO₅and have the best crystallinity when they areprepared under1550oC. The photoluminescence excitation and photoluminescencespectra of (Sr_x-1Ba_x)_3-ySiO₅: yEu²⁺show a broadband character with a peak located at365nm and592-609nm, respectively. By addition of Ba²⁺ions, the emission shifts tored light area at first and then shifts to blue area. The thermal stability is enhancedobviously while the luminescence intensity decreases. When the concentration of Eu²⁺is0.03mol, the intensity of emitting peak reaches the maximum and with the increasingof Eu²⁺, the emission peak moves to longer wavelength but the thermal stability getsworse. The choice and the content of flux were also investigated. The resultdemonstrates that BaF₂is the most qualified flux and when its content is1wt%, thephosphor exhibits the highest luminescence intensity.A novel oxynitride phosphor Sr_3-ySiO_5-6xN_4xwas firstly synthesized through solid-state reaction. The X-ray diffraction patterns illustrate that the preparedphosphors have the same crystal structure with Sr₃SiO₅and no other impurity phaseexist due to the incorporation of N^3-ions. The excitation spectra (λ_em=582nm) andemission spectra (λ_ex=460nm) exhibit broadband character with main peak locatedat363nm and581to585nm, respectively. With the increase of N^3-ions, both theluminescence intensity and the thermal stability are enhanced effectively.The luminescence properties of Ba²⁺, N^3-co-doped phosphor(Sr_0.8Ba_0.2)_2.97Eu_0.03SiO_3.02N_1.32 were studied. According to the X-ray diffractionpatterns, the synthesized phosphors also have the same crystal structure with Sr₃SiO₅.The emission of the synthesized phosphor is peaking at604nm under blue lightexcitation. The presence of nitrogen may increase the symmetry of the host lattice,which enhanced the luminescence intensity. In comparison with(Sr_0.8Ba_0.2)_2.97Eu_0.03SiO₅, not only the luminescence intensity but also the thermalstability is improved effectively. This novel oxynitride phosphor may be a potentialcandidate to increase the red component in traditional WLEDs.