【作者】 胡江峰；

【导师】 章少华；

【作者基本信息】 南昌大学 ， 材料物理与化学， 2010， 硕士

【摘要】 白光LED具有耗电量小、寿命长、环保、响应速度快等优点,被誉为继白炽灯、荧光灯之后的新一代照明光源。而白光LED用荧光粉作为半导体照明技术的关键材料之一,它的发光特性直接决定了白光LED的亮度、显色指数、相关色温及效率等性能。本文利用高温固相法制备了Ca2MgSi2O7:Eu2+, R3+(R=Ce3+, Y3+, Pr3+和Gd3+)和Sr4Si3O8Cl4:Eu系列荧光粉,利用X射线粉末衍射(XRD)和荧光光谱(FL)等方法进行表征,研究了这两种荧光粉的发光性能。结果表明,采用CaCl2作助熔剂同时又作反应物,利用高温固相法在碳还原气氛下合成了Ca2MgSi2O7:Eu2+荧光粉,确定其最佳的合成条件为CaCO3、Mg(OH)2、SiO2、CaCl2按摩尔比1.5：1：2：2.4称取原料；烧结温度为900℃；烧结时间为3h。合成的样品可被360nm-480nm的光有效激发,发射主峰为529nm的绿光。该荧光粉Eu2+的最佳掺杂浓度为0.02mol。与高温法相比,低温法制备的Ca2MgSi2O7:Eu2+荧光粉激发光谱形状出现差异,并且发射光强度显著增强,其中Ca2MgSi2O7:0.02Eu2+增加261%。Ca2MgSi2O7:Eu2+样品中引入Ce3+或Y3+离子都能使荧光粉的发光强度增强。采用高温固相法合成了Sr4Si3O8Cl4:Eu2+荧光粉,研究发现少量Zn2+的掺入没有改变样品的晶体结构,但使其发光强度显著提高,这可归因于Zn2+能减小Eu2+在晶体中局部浓度不均匀而产生的浓度猝灭现象及其助熔剂效应。当Zn2+掺杂过量时,会产生Sr2ZnSi2O7杂相,导致Sr4Si3O8Cl4:Eu2+发光强度降低,但仍比未掺Zn2+时的强。Sr4Si3O8Cl4:Eu3+可以被266nm,405mm的紫外光和464nm的蓝光有效激发,发射主峰为615nm的红光,当掺入Bi3+时,Sr4Si3O8Cl4:Eu3+荧光粉的发光强度显著增强,说明Bi3+对Eu3+发光有很强的敏化作用,Bi3+与Eu3+间存在能量传递。更多还原

【Abstract】 White LED has attracted a great deal of attention especially for general lighting, due to its low power consumption, long life, environment friendly and reliability. Phosphor is one of the key materials for white LED, and its fluorescence spectra can determine the luminance, Color Rendering Index (CRI), colour temperature and luminous efficacy.In this dissertation, Ca2MgSi2O7:Eu2+, R3+(R=Ce3+, Y3+, Pr3+, Gd3+) and Sr4Si3O8Cl4: Eu2+ phosphors were synthesized by the high-temperature solid state reaction method. The crystallization phase structure and the lumenscent properties of the samples were characterized by X-ray diffraction and spectrometer.Alkaline earth silicate Ca2MgSi2O7:Eu2+ phosphors were prepared under a reducing atmosphere by solid-state reaction using CaCl2 as flux medium and starting materials. Phosphors prepared with different CaCO3 amount, at different temperatures and time were obtained. The effect of these factors on the phase structure was studied by X-ray diffraction (XRD). The synthetic conditions were optimized at the molar ratio of starting materials CaCO3, Mg(OH)2, SiO2, CaCl2 equal to 1.5:1:2:2.4, sintering temperature 900℃and soaking time 3 h. The fluorescence spectra of the as-prepared phosphor powders were measured. The results indicated that the Ca2MgSi2O7:Eu2+ phosphor can be effectively excited by the light in the wavelength range of 360nm～480nm and emission spectrum shows a broad green emission band centered at 529nm, leading to a bright green emission. The Ca2MgSi2O7:Eu2+ phosphors were also synthesized at 1200℃for 4 h in a reducing atmosphere using H3BO3as flux medium and CaCO3, Mg(OH)2, SiO2 as starting materials. Comparing the high temperature method with low temperature methods, we found that their exitaiton spectrum profiles were different, and the emission intensity of Ca2MgSi2O7:xEu2+(x=0.01,0.02,0.03, 0.04,0.07) phosphor prepared at 900℃was higher than those prepared at 1200℃. The doping of Ce3+ or Y3+ can enhance the fluorescent intensity of Ca2MgSi207:Eu2+ phosphors. These results showed that co-doping with Ce3+ can enhance the fluorescent intensity due to the energy transfer process from Ce3+ to Eu2+ in Ca2MgSi2O7:Eu2+, Ce3+ phosphors, and that co-doping with the Y3+ can increase the fluorescent intensity because of the charge defects resulting from the co-doping Y3+ ion in Ca2MgSi2O7:Eu2+, Y3+ phosphors.Sr4Si3O8Cl4:Eu2+ phosphors were also synthesized by the solid-reaction at high temperature. The emission intensity reaches a maximum at 0.08 of Eu2+ concentration. The effects of Zn2+ on the crystallization behavior and photoluminescence (PL) properties of Sr4Si3O8Cl4:0.08Eu2+ phosphor were studied. Results suggested that no new phase was introduced by co-doping with a small amount of Zn2+ ions, but when co-doped with excessive amount of Zn2+ ions, Sr2ZnSi2O7 appearsed. It was found that the co-doping of a small amount of Zn2+ could remarkably improve the PL intensity of Sr4Si3O8Cl4:0.08Eu2+ When x=0.05, the intensity of Sr4Si3O8Cl4:0.08Eu2+,xZn2+ was increased up to 2.3 times that of pure Sr4Si3O8Cl4:0.08Eu2+, which could be attributed to the flux effect of Zn2+ ions, and the reduction of energy transfer between Eu2+ by Zn2+ doping. Sr4Si3O8Cl4:Eu3+ phosphor can be effectively excited by the 266nm,405nm,464nm light, and its emission spectrum mainly center at 615nm. Doping of Bi3+ can enhance the fluorescence intensity of :Eu3+ phosphors because of the energy transfer between Bi3+ and Eu3+.更多还原