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1、太原理工大学 硕士学位论文 白光LED用YAG荧光粉的合成与研究 姓名：侯建新 申请学位级别：硕士 专业： 指导教师：周禾丰 20090501 太原理工大学硕士研究生学位论文 I 白光 LED 用 YAG 荧光粉的合成与研究 摘 要 YAG:Ce3+荧光粉具有化学稳定性高、硬度大、高熔点、寿命长等优点， 且与蓝光 LED 芯片组合能够混合成视觉上的白光，组成白光 LED。但是荧 光粉的发射光谱中缺少红光成分造成了白光 LED 的色温偏高，显色指数偏 低。传统的钇铝石榴石（YAG）荧光粉普遍采用高温固相反应法（1600 1800） ，高温固相法利于工业化生产，但反应温度过高，周期较长，对设 备要
2、求较高，粒子易团聚，最终制得的产品颗粒尺寸大，需球磨方可使用， 而球磨会使发光体的晶形受到破坏，发光效率大幅下降。最近人们通过水 热法、燃烧法、微波加热法和溶胶-凝胶法等方法来合成 YAG 荧光粉。 在对几种合成荧光粉方法进行较充分研究的基础上，本文开展了 YAG 荧光粉的合成与发光特性的研究。用高温固相法合成了性能优良的 YAG :Ce3+荧光粉，确定了 Ce3+的最佳掺杂浓度，并对其合成工艺进行了优 化。 在此基础上基于 YAG :Ce3+荧光发射光谱中缺少红光成分的缺点对其进 行了 Pr3+的掺杂，合成了的 YAG:Ce3+,Pr3+荧光粉，研究了其光谱性能，并 对 Pr3+的掺杂量对发
3、光性能的影响进行了较为系统的研究； 分别用高温固相 法和高分子网络凝胶法合成了 YAG:Ce3+,Gd3+荧光粉，研究了其光谱性能以 及 Gd3+的掺杂对其发光性能的影响，并对两种合成方法进行了对比。 对荧光粉的 XRD 结果进行分析得出，无论用哪种方法，最终合成的产 物均为体心立方晶系的钇铝石榴石结构，具有 Oh(10)2Ia3d 的空间群，但是 高温固相法得到的产物的结晶程度要好一些。 太原理工大学硕士研究生学位论文 II SEM 表明用优化工艺后的高温固相法合成的 YAG :Ce3+、 YAG:Ce3+,Pr3+ 和 YAG:Ce3+,Gd3+荧光粉的颗粒尺寸都在 12m 左右，而高分子
4、网络凝胶 法合成的 YAG:Ce3+,Gd3+荧光粉的颗粒尺寸在几百纳米之间，颗粒小，更利 于荧光粉的应用。 荧光光谱分析表明： （1）YAG:Ce3+,Pr3+荧光粉激发光谱为双峰结构，激发主峰位于 460nm 附近。产物的发射光谱也是双峰结构，分别是位于 530nm 附近 Ce3+的 5D2F 5/2特征发射峰和位于 610nm 附近 Pr 3+的1D 2 3H 4特征发射峰， 610nm 处红光发射峰的出现有望能提高白光 LED 的显色指数。通过对不同 Pr3+掺 杂浓度荧光粉的发射光谱强度进行对比，确定了最佳的 Pr3+掺杂浓度。 （2）采用高温固相法和高分子网络凝胶法合成的 YAG:
5、Ce3+,Gd3+荧光 粉的激发光谱也是双峰结构，主激发峰都位于 460nm 附近。发射光谱分别 位于 539nm554nm 和 523nm546nm 之间，随着 Gd3+掺杂浓度的增大， 发射峰发生了红移，本文用位形坐标解释了这一现象。所以 YAG:Ce3+,Gd3+ 荧光粉可以满足不同波长蓝光 LED 的要求，且由于发射光谱的红移，有望 提高白光 LED 的显色指数。 （3）通过对高分子网络凝胶法和高温固相法制备的产物的各项参数对 比得出，高分子网络凝胶法具有广泛的应用前景。 关键词：YAG 荧光粉，高温固相法，高分子网络凝胶法，稀土掺杂，红移 太原理工大学硕士研究生学位论文 III SY
6、NTHESIS AND STUDY OF YAG PHOSPHOR USED IN WHITE-LIGHT LED ABSTRACT Cerium doped yttrium aluminitum garnet (YAG:Ce), which has the advantage of high chemical stability, high hardness, high melt point and long life-time et al., is a comprehensively studied phosphor which is used as a yellow-emitting c
7、omponent for the production of a white light. A combination of a blue light emitting diode (LED) and a yellow phosphor is a widely adopted type for a white light production because of its low fabrication cost and high luminous efficiency. However, a yellow-emitting YAG:Ce phosphor-based white LEDs i
8、nherently suffer from poor color rendering properties due to the red spectral deficiency. For the purpose of widening the color gamut of white LEDs, the emission of YAG:Ce phosphor may be tailored through the incorporation of an additional codoping element or through the substitution of a YAG host.
9、YAG phosphors are prepared by solid state reaction (16001800) conventionally, which is in favor of industrial production. But it has more demanding on the equipment, sintering temperature and periods. Large particles size results from reunion easily. Fine phosphors can be obtained by grounding. Howe
10、ver, it may cause the poor crystallinity and the decreasing luminescent 太原理工大学硕士研究生学位论文 IV efficiency. Recently, YAG phosphors have been synthesized by hydrothermal method, combustion method, microwave heating method, sol - gel method and other methods. In this paper various YAG:Ce-based phosphors c
11、hemically modified by Pr-codoping/ Gd-substitution were synthesized via high temperature solid state reaction and a soft chemistry, respectively. The luminescence properties of YAG phosphors were studied in detail. The YAG:Ce3+ phosphors of excellent performance were synthesized by high temperature
12、solid state reaction. The synthesis process was optimized and the best doping concentration of Ce3+ was identified. As for the codoped/ substituted YAG:Ce system, YAG:Ce3+, Pr3+ and YAG:Ce3+, Gd3+ phosphors were synthesized by high temperature solid state reaction and polymer network gel method. The
13、ir spectrum performance and the effect on luminescent properties of the doping amount of Pr3+ or Gd3+ were discussed respectively. Finally, this two kinds of synthesis methods of YAG:Ce3+, Gd3+ phosphors were compared. It is known that the three phosphors has body-centered cubic crystal structure of
14、 yttrium aluminum garnet with the space group of Oh(10)2Ia3d by analyzing the XRD pattern. The products synthesized by high temperature solid state reaction have better crystallinity. SEM images show that the particle sizes of YAG:Ce3+、YAG:Ce3+, Pr3+ and YAG:Ce3+,Gd3+ phosphors synthesized by high t
15、emperature solid state reaction are all at 12m , while the particle sizes of YAG:Ce3+,Gd3+ phosphors 太原理工大学硕士研究生学位论文 V synthesized by polymer network gel method are at a few hundred nanometers, small particles is convenient for application of phosphors. Results of the spectra show that: (1) The exei
16、tation spectra of YAG:Ce3+,Pr3+ phosphor have two peaks. The major one is around 460nm. The emission spectra also have two peaks which is the characteristics emission peaks of Ce3+ attributed to the 5D2F5/2 transitions at 530nm and the characteristics emission peaks of Pr3+ attributed to the 1D 2 3H 4 transitions at 610nm respectively. The 610nm red light emission peak is expected to improve the color-rendering index of white light LED. Compared to emission intensity of phosphors
