Study On The Modulation Of Composition And Photoluminescence Properties Of Oxynitride Phosphors

Currently,white LEDs are considered to be the fourth generation of lighting sources.Compared with traditional light sources,white LEDs have many advantages.White LEDs are non-toxic and environmentally friendly,and they are green light sources.Among the technologies for realizing white light LEDs,phosphor-converted white light LEDs have become the mainstream of white light LED preparation due to the mature technology and simple structure and low cost.Compared with other phosphors,silicon-based oxynitrides have attracted attention due to their good chemical and thermal stability.In this paper,based on a series of studies on silicon-based oxynitride,two rare earth/transition metal ion-doped silicon-based oxynitride fluorescent materials were prepared under normal pressure,and their structures,microscopic morphology and optical properties were explored in detail.（1）Doping aluminum nitride and boron nitride in CaSi₂O₂N₂:1%Ce³⁺phosphors can blue-shift the emission spectrum and enhance the emission intensity significantly.Compared with the single-doped Ce³⁺ions,the emission spectrum of CaSi₂O₂N₂:Mn²⁺-Ce³⁺phosphors is blue-shifted,and the luminous intensity of the co-doped phosphors is greatly improved compared with the corresponding single-doped phosphors.The strongest emission peak of CaSi₂O₂N₂:Dy³⁺phosphor is a linear yellow emission at 585 nm,which comes from ⁴F_9/2→⁶H_13/2 of Dy³⁺.The emission spectrum of CaSi₂O₂N₂:Dy³⁺-Ce³⁺phosphors has an asymmetric broadband around 460 nm and a smaller peak at 582 nm.In the CaSi₂O₂N₂:Dy³⁺-Ce³⁺phosphor system,there is a phenomenon of energy transfer from Ce³⁺ions to Dy³⁺ions.（2）The effects of various fluxes on the phase composition,microstructure and luminescence properties of CaSi₂O₂N₂:Eu²⁺phosphors were investigated.The phosphor samples prepared by adding different fluxes showed different photoluminescence properties,and the optimal emission peak was located at 548 nm.At a relatively low heating temperature（1400℃）,Ba F₂ is the best flux,which is beneficial to obtain pure CaSi₂O₂N₂ phase,and the phosphor samples have good morphology and the strongest luminescence intensity.At higher temperatures,CaCl₂ is the best choice.The quantum efficiency of the samples was greatly improved after adding flux,especially the samples with Ba F₂ added.（3）The effects of the size and type of raw materials on the luminescence properties of Ca₂Si₃O₂N₄:Eu²⁺orange-red phosphors were studied in detail.Using Ca₅（PO₄）₃OH with smaller size as raw material can make the morphology of the synthesized samples better.The Ca₂Si₃O₂N₄:1%Eu²⁺phosphor exhibits orange-red emission centered at 600nm.Using Ca₅（PO₄）₃OH with a smaller size as the raw material,the color coordinates of the Ca₂Si₃O₂N₄:1%Eu²⁺phosphor gradually moved from the yellow-green region to the red-orange region,the quantum efficiency of the phosphor was improved,and the fluorescence decay time was reduced.The concentration quenching mechanism of Eu²⁺ions in Ca₂Si₃O₂N₄:Eu²⁺phosphors is electric dipole-electric dipole interaction.