Preparation Of Europium-Containing Silicon Oxynitride Phosphor Doped By Magnesium With High Quantum Efficiency

The europium?Eu?-doped silicon oxynitride phosphor with stable physicochemical properties and simple phase structure has been successfully synthesized via a novel polymer-derived method.However,the photoluminescence properties?quantum efficiency?of those phosphors need to be further improved.It has been found that doping with appropriate amount of magnesium?Mg?ion could highly enhance the photoluminescence?PL?intensities of rare earth doped alkaline earth silicon oxynitride and cerium-doped silicon oxynitride phosphors,however,the effects of Mg-doped on Eu-containing silicon oxynitride phosphor prepared by polymer-derived method are not clear yet.Therefore,it's necessary to investigate how to prepare Eu-containing silicon oxynitride phosphors with simple structure and high quantum efficiency by doping of Mg.In this work,the investigation on preparation of Mg doped Eu-containing silicon oxynitride phosphor with high quantum efficiency by polymer-derived method via polycarbosilane,Eu-acetylacetonate and Mg-acetylacetonate was come out.The effects of sintering methods,sintering temperature and nominal molar ratios of silicon?Si?,Eu and Mg on the chemical composition,phase structure,morphology and PL properties of phosphors were systematically studied by element analysis,XRD,SEM and PL spectrum.A Mg doped Eu-containing silicon oxynitride phosphor with a high quantum efficiency was successfully synthesized.The HRTEM,Raman spectrum and XPS were also employed to study the microstructure of the Eu-containing phosphor with strongest PL intensity and the Mg doped Eu-containing phosphor with high quantum efficiency.The results show that the two-step sintering process could reduce the carbon content,purify the phase structure,prevent clumping and significantly enhance the PL intensities of phosphors comparing with the one-step sintering process.The major phases of phosphors were Si₂ON₂ and ?-Si₃N₄ when the sintering temperatures are 1400 ? and 1650 ?,respectively.The emission wavelength of phosphors sintered at 1400 ? remain in the region of blue light?420-475 nm?regardless of the nominal molar ratio of Si,Eu and Mg.However,the emission wavelength of phosphors exhibits a red shift from blue light region to a yellow-orange light region with the increasing of Eu content when the phosphors was sintered at 1650 ?.Both phosphors with and without Mg doped have strongest PL intensities when the nominal molar ratio are Si:Eu=32:0.1 and Si:Mg:Eu=31.3725:0.6275:0.1,respectively.The Eu-doped phosphor(SiO_0.069N_1.560C_0.013Eu_0.0022)with strongest PL intensity and Mg doped Eu-containing phosphor(SiO_0.289N_1.222C_0.011Eu_0.0012Mg_0.012)with high quantum efficiency could be prepared via the two-step sintering process sintered at 1650 ?.Both phosphors have rod-like,and almost single crystalline particles,an excitation band centered at 340 nm,and a strong emission band centered at 430-440 nm with a shoulder emission band centered at 550 nm.Compares to the Eu-containing phosphor,Mg doping enhanced the PL intensity 2.73 times,improved the internal quantum efficiency to 93.81%,reduced the content of carbon to 2.5%,and increased the percentage of Eu²⁺ species of the phosphor.