Preparation And Properties Of Mg-Ge,Ga Doped YAG:Ce³⁺/Sm³⁺ Phosphors

YAG:Ce³⁺,Sm³⁺phosphors,Mg²⁺-Ge⁴⁺doped Y_2.94Al_5-2xMg_xGe_xO₁₂:Ce³⁺_0.06 phosphors and Ga³⁺doped Y_3-y-y Al_5-xGa_xO₁₂:Ce_y³⁺（YAGG）phosphors were prepared by high temperature solid state reaction method.The major study context in this thesis includes those:（1）The effects of different fluxes,sintering temperatures and times on the morphology,structure and luminescent properties of the YAG:Ce³⁺phosphors were studied.X-ray diffraction（XRD）,fluorescence spectrophotometer（PL）and scanning electron microscope（SEM）were used to analyze the samples.The results indicate that the samples with 4%BaF2as flux sintered at 1600℃for 5 h exhibit an good morphology and luminescent properties.When co-doped with Sm³⁺ions,a series of new emission peaks appears in the emission spectra of the samples in the red region,and the color temperature of the white LED was reduced and the color increased gradually.（2）The effects of Mg²⁺-Ge⁴⁺concentrations on the morphology,structure,luminescence properties,fluorescence lifetime and white LED performance of YAG:Ce³⁺phosphors were studied in detail.X-ray diffraction（XRD）,Scanning election microscope（SEM）,Photoluminescence（PL）spectra and so on were used to characterize the samples.The results indicate that Mg²⁺-Ge⁴⁺ion pairs can partially substitute the Al³⁺ions of YAG successfully.With the substitution,the garnet crystal structure remains unchanged.However the emission spectra show a progressive red-shift,from 528 to 552 nm.The lifetime decreased rapidly and the particle size increased gradually.In particular,the correlated color temperature（CCT）decreased gradually and the color rendering index（CRI）increased to 89.3.（3）The optimal doping concentration of Ga³⁺and Ce³⁺in YAGG matrix and the luminescence and energy transfer properties of samples were discussed in detail.X-ray diffraction（XRD）and fluorescence spectrum techniques were used to analyze the samples.The results indicated that,the emission spectra of the samples show a progressive blue-shift with the doping of Ga³⁺,and the luminescence intensity increased first and then decreased.When 0.75 Al³⁺ions were substituted,the samples showed the best luminescence.In the YAGG matrix,the optimal doping concentration of Ce³⁺is 0.1.When Sm³⁺was co-doped,energy transfer from Ce³⁺to Sm³⁺ions was demonstrated in YAGG host,and the energy transfer type from Ce³⁺to Sm³⁺ions was supposed to be a resonant type through dipole-dipole.