【作者】 张纳；

【导师】 李岚； 王达健；

【作者基本信息】 天津理工大学 ， 凝聚态物理， 2006， 硕士

【摘要】 白色发光二极管（WLED）的问世,是半导体技术的发展在引发微电子革命后又在孕育一场新的产业革命——照明革命。由于WLED体积小、耐振动、响应速度快、寿命长、无污染等优点,将成为替代白炽灯、荧光灯和高强度气体放电灯之后的第四代光源。目前市场上销售的白色发光二极管结构为蓝色LED芯片和可被蓝光有效激发的发黄光荧光粉（YAG:Ce）有机结合组成白光LED。如今白光LED的性能距离照明用标准还有一定差距,因此作为LED上游基础材料的一个重要组成部分,YAG:Ce荧光粉的性能仍需要改善提高。本工作以铈激活的钇铝石榴石荧光粉（YAG:Ce）为研究核心,分别采用新型和传统制备方法,通过掺杂和添加等手段,探索了改善荧光粉结构、形貌,提高发光性能的新途径,研究结果对该材料的大规模生产和性能优化具有重要意义。研究工作主要获得以下创新性的结果:1.详细研究了一种新的制备方法——溶胶喷雾热解法的技术细节,首次通过采用一种纳米尺度的拟薄水铝石原料,胶溶后,得到稳定的拟薄水铝石的复合水溶胶,再经过喷雾-热解得到免球磨的YAG:Ce荧光粉。突破了传统溶胶-凝胶法选用的金属醇盐形成溶胶的瓶颈,解决了传统固相合成法在纯相控制、颗粒尺度大以及高能耗的问题,YAG相在加热温度1000℃时就可以形成,制备获得的近球形晶粒平均粒度为3μm,粒度分布曲线明显窄化。2.从钇铝石榴石晶体结构和三价铈离子发光特性出发,以YAG为基质,通过掺杂的方法——与铈共掺不同离子(Gd³⁺、Ga³⁺、Pr³⁺、Eu³⁺、Ho³⁺、Mg2+),改变基质中的阳离子、阴离子基团部分取代,考察晶格结构对Ce³⁺的影响及不同稀土离子与铈的能量传递,探索了以YAG为基质荧光粉发射波长调控的方法以及助熔剂对荧光粉发光强度的影响。结果表明,Mg2+的进入使发射波长向长波方向移动,从而有助于改善LED器件的色纯度。添加碳酸盐类助熔剂为0.006mol时,发光强度提高6倍。3.从理论上分析了球形颗粒形成机理,在此基础上获得形成球形颗粒的YAG:Ce荧光粉的实验条件。分别选用正硅酸乙酯（TEOS）、聚乙二醇（PEG）、十六烷基三甲基溴化胺（CTAB）为添加剂,研究添加剂对喷雾热解法制备荧光粉的影响。加入TEOS,Al2Y4O9和AlYO3杂相能被有效抑制,在900℃、1100℃、1200℃烧结温度下均观察到球形形貌。分别添加PEG和CTAB时,没有观察到球形形貌。4.对比研究了固相法、传统溶胶-凝胶和溶胶喷雾热解法的区别。以纳米级拟薄水铝石为铝源制备的复合胶体溶胶-凝胶法和喷雾热解法能在较低的温度（1000℃）下获得YAG相,在1400℃获得YAG纯相。新的制备方法在资源、环境、性价比、放大性方面具有显著优点,容易获得相纯、免球磨的荧光粉,解决了溶胶-凝胶法制备干凝胶遇到的问题。更多还原

【Abstract】 White light-emitting diodes （WLED） are poised for another revolutionizing the luminescence lighting industry after semiconductor technology leading to micro-electronics revolution and have the potential of replacing the conventional incandescent, fluorescent and discharge-column-type fluorescent lamps for small volume, endurable vibration, long lifetime, non-pollution etc. Nowadays the blue LED chip combined with yellow cerium doped yttrium aluminum garnet phosphors （YAG:Ce） is the most common pattern to produce white light. However as a important component of producing LED, the capabilities of YAG:Ce phosphors still need improved.This work is to aim at the yttrium aluminum garnet luminous powder which activates by the cerium （YAG:Ce） by using a novel and a traditional preparation method respectively and by changing doping strategy. The more attentions are paid to adjustment of microstructure and morphology and improvement of the luminescence performance. The expected findings have the vital significance to this material for large scale production and the further optimization of properties.We have drawn some creative conclusions as follows:1. A novel preparation method----sol-spray pyrolysis method was investigated experimentally in detail. By using a special kind of nano-sized pseudo-boehmite power as starting material, after peptizing, a stable composite hydrosol was obtained, then this sol was sprayed to xerosol and sintered to YAG:Ce fluorescent materials without any further ball-milling treatment. The bottleneck of selecting metal alkoxides in the traditional sol-gel was broken and the problems which controlling pure phrase,large grain size and high energy consumption met in traditional solid state method were overcome. At 1000℃, YAG phrase can be obtained, the near sphere grain’s average crystal size is around 3μm and the grain-size distribution of phosphor particle is obviously narrow.2. To investigate the mechanisms of luminescence properties and to optimize the luminous parameters, we examine a series of doping effects. Taking YAG as host, through doping method----co-doping different irons with cerium (Gd³⁺,Ga³⁺,Pr³⁺,Eu³⁺,Ho³⁺,Mg2+), changing partial substitutions positive ion and anion groups of the host, how the changed host effects on the luminescence to Ce³⁺ was studied. The energy transfer among different rare earth ions and Ce³⁺ is analyzed and how to adjust the phosphor’s emitting wavelength was also approached. Furthermore, the influence of the flux（Li2CO3） on the luminescence intensity of phosphor was examined. The results indicate the doping of Mg2+ ion leads to red shift of the emitting wavelength, so it helps to improve colour character of LED. The optimized amount of flux Li2CO3 is ca. 0.006mol, the luminescence intensity with flux is 6 times higher than that without flux. 3. The spherical granulation mechanism has been analyzed theoretically. Based on the theoretical results, the experimental process parameters to obtain sphere-like YAG:Ce phosphors are obtained. The additives of tetraethoxysilane （TEOS）、polyethylene glycol （PEG） and cetyltrimethyl ammonium bromide （CTAB） were tested. It is found that by adding TEOS, Al2Y4O9 phase with AlYO3 phase could be effectively suppressed, while spherical morphology could be received at around 900℃、1100℃and 1200℃respectively. Consequently, the luminous intensity is 3 times to that without using TEOS under the same sintering condition. On the contrary, the spherical morphology was not achieved by using PEG and CTAB respectively.4. The comparative test among solid state method, traditional sol-gel and this sol-spray pyrolysis was evaluated experimentally. We found that the sol-gel and spray pyrolysis method with nano pseudo-boehmite particulates as aluminium source could produce YAG phrase relatively easily at lower temperature（ca. 1000℃）and obtain pure YAG phrase at 1400℃. Moreover, the new spray pyrolysis method is much easier to receive pure phase without necessity of ball-milling treatment. Hence, the new preparation method of sol-aided spray pyroloysis has the remarkable merits in the resources, environment, price and value, enlargement production. The drawbacks of lowering brightness upon tradition milling treatment in traditional sol-gel method can be overcome by this novel route.更多还原