Synthesis,Optical Properties And Thermal Stability Of Blue-Green Nitrogen Silicon Phosphors

Phosphor-converted WLED has been used in the market for many years because of small size,reliability,efficiency,superior lifetime,environmental friendly.The optical properties,thermal stability and color matching scheme of phosphor play a key role in the photoelectric parameters and properties of LED.Nitridosilicate phosphors have excellent stability due to SiN₄ tetrahedra,which attracts much attention.However there are many problems limit the development,such as complicated preparation process,high equipment precision,high production cost,difficult to industrialize.At the same time,the simple sample has many disadvantages,such as impure phase,poor uniformity,serious agglomeration and so on.It seriously affects the absorption and optical properties of phosphor.Therefore,it is extremely urgent to study the synthesis and surface treatment technology of phosphor.This paper aims to solve the existing problems by studying different preparation and surface treatment.And analysing in multidimensional view with luminescent properties and thermal stability of phosphor.Meanwhile,the sample combined with modern packaging technology into WLED,confirmed its potential application in the field of solid lighting.The specific research contents are as follows.1.LaSi₃N₅:Ce³⁺blue phosphor for white LED was synthesized by carbothermal reduction method.The effect of synthesis temperature on the sample was studied,and the optimum temperature is 1600?.Study on the influence of the crystal structure and luminescence properties of activated carbon on the synthetic samples.The results show that the luminescence intensity increased then decrease with the content of activated carbon changing.And the content of C is n_c/n _La=4:1 presents the best luminescence properties.The spectral peak position appear red shift then blue shift phenomenon.The effect of annealing on sample was studied.It was found that the luminescence intensity increased 60%-345%,and the phase became more purity.A stable white LED was obtained by self-made LaSi₃N₅:Ce³⁺blue phosphor.2.(Ba_1-x?Sr_x)Si₃O₄N₂:Eu²⁺green phosphor for white LED was synthesized by high temperature solid-state method.The effect of synthesis temperature on the sample was studied,and the optimum temperature is 1175?.The influence of different washing processes on the luminescent properties of phosphors was studied.The most suitable treatment was determined by dilute hydrochloric acid washing.With the increase of Sr content,the XRD shifts to the right of the diffraction angle due to the substitution of Sr for Ba in the main lattice.The excitation spectrum is quite broad,expanding from the near-UV to visible region?250-500nm?,which is corresponded to the crystal field splitting of the 5d orbital due to the 4f⁷-ground state to the 4f⁶5d-excited state of the Eu²⁺ions electronic transitions from Eu²⁺ions.The emission spectrum exhibits an symmetrical band ranging from 470nm to 630nm with a maximum at 527nm,and the content of Sr is 10%presents the best luminescence properties.The sample has excellent thermal quenching properties,and still has excellent thermal stability while the environment is 200?.Packaging the sample with red phosphor CaAlSiN₃:Eu²⁺and blue chip.The color temperature of WLED is2902K,the color coordinate is located?0.4456,0.4093?,the Ra is 97.4,and the R9 is97.3,which meets the demand of white light lighting.3.Nano SiO₂ were prepared by sol-gel method,and the(Ba_1-x,Sr_x)S_i3O₄N₂:Eu²⁺@SiO₂ were further synthesized.The effect of the synthesis process of SiO2 on the morphology,particle size and uniformity of the particles was studied.The results showed that the particle size of SiO₂ increased gradually with the increase of the concentration of NH₄OH,while the concentration of TEOS had little effect.The effects of coating thickness on the structure,morphology and luminescence properties of(Ba_1-x,Sr_x)Si₃O₄N₂:Eu²⁺@SiO₂ were investigated.The results show that the SiO₂ coated with phosphor on the surface of the form exists in the system.It will not destroy the crystal structure of(Ba_1-x,Sr_x)S_i3O₄N₂:Eu²⁺?The luminescent properties significantly enhance when adding phosphors are 1g.