【作者】 史玉茸；

【导师】 王育华；

【作者基本信息】 兰州大学 ， 材料物理与化学， 2014， 博士

【摘要】 白光发光二极管(light emitting diodes,LED)以其节能环保等显著优势,被广泛誉为第四代照明光源。而作为市场主流的荧光转化型白光LED(简写pc-LED)更是受到广泛的关注,荧光粉性能的优劣直接影响到白光LED器件的性能。目前pc-LED实现白光的方式主要分为两大类：蓝光芯片匹配YAG:Ce黄色荧光粉和(近)紫外芯片匹配红绿蓝三基色荧光粉。针对现有pc-LED角荧光粉存在的问题,本论文重点研究了Ce3+掺杂石榴石结构和黄长石结构硅铝酸盐的发光性质及其在pc-LED上应用的潜力；同时,还研究了Eu2+掺杂Ca7(PO4)2(SiO4)2的发光性质及其在pc-LED上应用的可能性。主要研究内容如下：第一部分：针对现有蓝光芯片用YAG:Ce黄色荧光粉存在的瓶颈问题,我们从商用粉改进和新材料开发两个方面分别做了如下工作：1.研究了YAG基质中Ce3+-Mn2+毙量传递现象和电荷补偿剂离子对Ce3+-Mn2+能量传递效率的影响。研究发现Mn2+在YAG晶格中占据三个格位,分别发射绿光、橙光和深红光。通过调整Mn2+的含量,可以实现光谱从黄绿到红光直至深红光的转变。电荷补偿剂的种类对Ce3+-Mn2+能量传递效率影响很大,使用Si4+作为电荷补偿剂时Ce3+-Mn2+能量传递效率最高。通过这部分研究,获得了发光性能优异的黄色发光材料YAG:0.06Ce,0.04Mn,0.04Si,其具有较高的亮度,很好的热稳定性及较高的量子效率,其与蓝光复合后有望获得显色指数较高的白光。2.使用固相法获得了主相为Y2.94Ce0.06Mg2AlSi2O12的样品,其可被460mm蓝光有效激发,发射主峰位于600mm的红光。蓝光与红光组合不能获得白光,同时不同温度下荧光光谱测试结果表明Y2.94Ce0.06Mg2AlSi2O12的热稳定性较差。因此,我们研究了Mg2+-Si4+离子对和Lu3+掺杂对Y2.94Ce0.06Mg2AlSi2O12发光材料光谱性能和热稳定性的影响,研究结果表明Lu3+完全替代Y3+时,样品具有理想的光谱性能和很好的热稳定性。3.使用固相法制备了主相为Lu3MgAl3SiO12:xCe的系列样品,并使用结构精修的方式确定了结构。光谱测试结果表明Lu3MgAl3SiO12:xCe可被450nm蓝光有效激发,发射主峰位于560nm的黄光,且Lu3MgAl3SiO12:Ce具有很好的热稳定性,证明其具有作为蓝光芯片用黄色荧光粉的潜力。第二部分：研究了系列阳离子和阴离子集团取代对LaCaAl3O7:Ce3+黄长石结构化合物的影响。我们从三个方面对LaCaAl3O7进行取代,分别为Gd3+、Y3+和Tb3+取代La3+的位置；Sr2+和Ba2+取代Ca2+的位置；B3+、Ga3+和Si4+取代A13+的位置。研究发现La3+格位的取代对Ce3+的光谱位置影响最大,Ca2+的取代次之,对A13+位置的取代效果最弱。另外,研究发现,Y3+完全取代时具有最高的发射强度,说明YCaAl3O7:Ce较LaCaAl3O7:Ce更适合作为紫外芯片用蓝色发光材料；且随着Si4+取代量的增加发射光谱强度增加,表明硅酸盐黄长石结构较铝酸盐黄长石结构更适合作为Ce3+掺杂的发光材料基质。第三部分：采用高温固相法制备了Ca7(PO4)2(SiO4)2:Eu2+单相样品。Ca7(PO4)2(SiO4)2:Eu2+在240-440nm存在很强的吸收峰,其在365nm激发下,发射出波长范围在400-700mm,峰值522mm的绿光。同时,我们研究了Ca7(PO4)2(SiO4)2:Eu2+中的浓度猝灭机理和激活能AE。但是很可惜很难对Ca7(PO4)2(SiO4)2:Eu2+进行改进,少量离子掺杂便出现第二相。更多还原

【Abstract】 Light emitting diodes (LED) has attached much attention due to low consumption of energy and environmentally friendly, especially for phosphor convert LED (pc-LED). Phosphors as an important part of pc-LED affected LED devices properties. Generally, two ways can be employed in obtaining white light:one is using yellow phosphor to convert blue light to obtain white light; the other is using three phosphors named as blue, green and red, to convert ultraviolet light into white light. Both of them have serious drawbacks. In this thesis, we mainly discussed photoluminescent properties of Ce3+doped garnet and melilite structure silicate-aluminum compounds. And also we investigated photoluminescent properties of Eu2+doped Ca7(PO4)2(SiO4)2. The main results are as follows:The first part:In view of the darwbacks of commercial YAG:Ce yellow phosphor, our work was done from two aspects like improvement of commercial YAG:Ce phosphor and looking for new materials which was suit for blue light excitation.1. The energy transfer phenomenon of Ce3+-Mn2+in YAG and how the charge compensators affect energy transfer efficiency was investigated. The emission spectra of Mn2+singly doped YAG samples show three bands:green, orange and deep red bands. The color can be tuned from yellow-green to red, even to deep red by increase Mn2+content. Besides, Quadrivalence ions are introduced to balance the charge difference between Mn2+and Al3+. Among them, Si4+as charge compensator exhibits the best tunable effect on controlling the Mn2+emissions in YAG:Ce,xMn. Y3Al5O12:0.06Ce,0.04Mn,0.04Si sample, which has higher brightness, little thermal quenching and higher quantum efficiency, can be used as candidate to obtain warm white light.2. Y2.94Ceo.o6Mg2AlSi2012was obtained by solid state reaction with little amount of impure phase, and its photoluminescent properties were also studied. The photoluminescent spectra show that Y2.94Ceo.o6Mg2AlSi2O12can be effectively excited by460nm and give red light peaked at600nm. White light cann’t be obtained by single Y2.94Ceo.o6Mg2AlSi2O12sample. Besides, Y2.94Ceo.o6Mg2AlSi2O12sample has worse thermal stability. Thus, we introduce Mg2+-Si4+and Lu3+into Y2.94Ce0.06Mg2AlSi2O12sample. The best photoluminescent properties can be obtained by Lu3+completely substituted Y3+.3. We have presented the preparation and characterization of Lu3MgAl3SiO12:xCe phosphor for blue LEDs. XRD refinement results show LusMgAl3SiO12:xCe phosphor in garnet structure. The excitation and emission spectra show this new garnet phosphor can be excited efficiently by450nm and emit yellow color. Thermal quenching test indicates this new garnet phosphor has better thermal stability. All these characterization indicate Lu3MgAl3SiO12:xCe has high possibility use in LED.The second part:Luminescence spectra of LaCaAl3O7:Ce3+have been tuned by series of cationic and anionic group substitution. Three different types of isovalent substitutions in LaCaAl3O1:Ce3+was investigated:for trivalent La, by the smaller trivalent rare-earth, Gd3+, Y3+and Tb3+; for divalent Ca2+, by the bigger divalent Sr2+and Ba2+; for trivalent Al2+, by the smaller trivalent B3+, as well as by the larger trivalent Ga3+. The results show the substitution on trivalent La3+has the most obvious effect on Ce3+’s spectra. In addition, Y3+substitute La3+gives higher emission intensity, indicates YCaAl3O7:Ce3+is a better blue phosphor in ultraviolet LED use than LaCaAl3O7:Ce3+. And the emission intensity increase with increasing of Si4+amount, which demonstates that silicate melilite compounds is better as Ce3+doped host than aluminum melilite compounds.The third part:A novel green emitting phosphor of Eu2+doped Ca7(PO4)2(SiO4)2was synthesized. Ca7(PO4)2(SiO4)2:Eu2+showed an strong absorption band ranging from240to440nm. Under365nm excitation, all samples gave bright green emission peaked at522nm. The concentration quenching mechanism and the activation energy for thermal quenching are investigated. However, it is very hard to improve its photoluminescent properties due to easily produce impurity phases when we introduce other ions.更多还原