【作者】 田培静；

【导师】 程金树；

【作者基本信息】 武汉理工大学 ， 建筑材料与工程， 2010， 博士

【摘要】 全固体白光发光二极管(light emitting diode, LED)作为新一代照明光源,具有节能、环保、长寿命等优点。在白光LED的配色方案中,紫外LED芯片结合三基色荧光材料这一模式当前还难以用于大功率照明,但是由于其色品质的优越性,具有很大的发展前景。在这一模式下可以使用的众多荧光材料中,稀土掺杂硅酸盐基荧光材料已经成为一个研究热点,除了其固有的稳定性外,还具有优异的发光性能和潜在的余辉特性。硅酸盐基质的晶体和非晶体作为基质材料各有优缺点,而微晶玻璃作为一种晶态和非晶态共存的复合材料,兼具了晶体材料良好的发光性能及玻璃材料优异的物化稳定性,具有重要的研究价值。本文用整体析晶法和烧结法制得了Sm3+、Tb3+、Eu2+掺杂的钙镁铝硅系发光玻璃及微晶玻璃。借助X射线衍射、扫描电子显微镜测量手段探寻微晶玻璃的晶相种类与形貌；使用Jasco FP-6500型荧光光谱仪测量发光微晶玻璃的荧光光谱,并利用PMS-80增强型光谱分析系统得到光色的色品坐标；采用拉曼光谱、X射线衍射、X射线光电子能谱、研究了稀土掺杂微晶玻璃的结构；并用析晶动力学的方法和分形理论研究了该系统玻璃的析晶性能。结果表明：钙镁铝硅系玻璃不论析出主晶相为硅灰石或透辉石,晶体的生长方式为表面向内部生长。随着热处理温度的升高或热处理时间的延长,晶体逐渐长大,晶相含量增多。在透辉石玻璃中,稀土氧化物作为玻璃修饰体存在于玻璃网络结构中,热处理之后,几乎所有的稀土离子取代透辉石中的Ca2+存在于晶相中。Sm3+、Tb3+在钙镁铝硅系微晶玻璃中的发射、激发峰的位置不随环境、浓度等因素的变化而改变。Sm3+掺杂的试样在404 nm紫光激发下发出4G5/2→6HJ(J=5／2,7／2,9／2,11／2)跃迁引起的位于红光波段的可见光；在377 nm近紫外光的激发下,Tb3+掺杂的试样可以发出5D4,3→7F6,5,4,3引起的蓝绿波段的可见光。稀土掺杂的钙镁铝硅微晶玻璃,与同组成玻璃相比,具有更强的发光性能。荧光光谱强度大小与晶相含量多少密切相关,这点是由稀土离子所在环境的声子能量变化引起的。在硅灰石微晶玻璃中,当外加稀土氧化物Sm2O3或Tb4O7的量在实验范围内逐渐变大时,激发与发射谱线强度有明显增强。而在透辉石微晶玻璃中,随着Sm3+外加量由0.05 mol%增至0.30 mol%,出现由Sm3+间的交叉弛豫及能量传递引起的浓度猝灭现象；实验浓度范围内,在该微晶玻璃中没有发现Tb3+猝灭现象。Sm2O3、Tb4O7共掺杂的透辉石微晶玻璃可以在350nm-385nm波长下同时被激发出两种离子的特征发射。且350nm,355nm,380nm波长芯片激发下的试样发出的光皆在色品图中的白光区域内,并具有1800-5400K的低色温。Eu2+掺杂的透辉石及方石英为晶相的微晶玻璃,在355nm光的激发下可以得到442nm的蓝光发射峰。随着热处理时间的延长,荧光光谱强度增加,随着试验范围内Eu2+浓度的增加,浓度猝灭发生。在透辉石母体玻璃中,随着硼含量的增加,分相(乳浊)现象逐渐严重,并且热处理后硼含量较多的试样中容易析出次晶相方石英。随着硼含量的增多,Sm3+、Tb3+分别掺杂的微晶玻璃强度呈先增大再减小的趋势。还原剂的引入会抑制透辉石玻璃的析晶速率,此时玻璃的析晶符合扩散受限制的凝聚模型。本项目得到湖北省教育厅科学技术研究计划重大项目(20091g0041)的资助。更多还原

【Abstract】 White light emitting diode (white LED) is becoming a new lighting application as its efficient energy use, environment friendly and long life. Of the approaches to creating white light, the model of phosphors together with ultraviolet LED can not achieve high ligh output, but the outstanding color quality decide its exciting application prospects. In the phosphors of this model, the rare earth doped silicate phosphor gains great interest due to their stability and optical properties. Glass ceramic, as the glass and crystal composites, owns the excellent luminescence properties from crystal phase and outstanding machinability, high uniformity and stability from glass phase.Sm3+, Tb3+, Eu2+doped CaO-MgO-Al2O3-SiO2 luminescent glass ceramics were prepared by melting-quenching and sintering method in this paper. X-ray Diffraction (XRD) and scanning electron microscope (SEM) were availed to measure the crystalline phase and microstructure of the glass ceramics. Jasco FP-6500 fluorescence spectrometer was used to get the emission and excitation spectra of samples. The color coordinates were measured by PMS-80 spectral analysis system. The structure of rare earth doped glass and glass ceramics were studied by XRD, XPS and Raman spectroscopy. And the crystallization of this glass was discussed by the kinetic analysis and fractal geometry. The results indicate:The crystallization manner of CaO-MgO-Al2O3-SiO2 glass is surface crystallization, and the possible main crystal is diopside or wollastonite. The crystal content of glass ceramic increased as heat treatment temperature or the time icreasing. For the diopside glass, RE3+exist in the glass as networkmodifier, after heat treatment, all the RE3+enter the diopside lattice and replace Ca2+sites.With the increase of reheat temperatures, RE3+concentration and the precipitate of diopside, the wavelength of peaks of Sm3+and Tb3+in optical spectra has no change. Sm3+doped glass ceramics can emit red light due to transitions 4G(?)→6HJ (J=5/2,7/2,9/2,11/2) under the excitation of long UV and blue lights. Tb3+doped glass ceramics emit intense cyan color light due to transitions 5D4,3→>7F6,5,4,3 under UV excitation. The luminescence of the glass ceramics is stronger than corresponding glass. We also found the direct correlation between luminescent intensity and crystal content, which was caused by the changed phonon energy. In the wollastonite glass ceramics, the luminescence intensity is increased with the increasing of the Sm2O3 or Tb4O7 content. In the diopside glass ceramics, concentration quenching effect was observed in the Sm3+doped glass ceramic, but not found in Tb3+doped glass ceramics.The flurescent spectras of Sm3+and Tb3+codoped glass ceramics under 350nm-385nm excitation were consist of the characteristic spectrim of Sm3+and Tb+ respectively. After excitaition of 350nm,355nm and 380nm LED, the color coordinates of the emission light fall within the white region of the 1931 CIE diagram, with low color temperatures of 1800-5400K.The Eu2+doped diopside glass ceramics could emit 442nm blue light under 355nm excitation. After heat treatment, short-wave-length shift and increased intensity were found in the luminescent spectra. With the increase of heat treatment time, the luminescence intensity increased. And the concentration quenching effect appeared with the increasing of the Eu2+content.In the matrix glass, the increased B2O3 induced separate phase, and another crystal cristobalite beta precipitated. The luminescent intensity of Sm3+and Tb3+doped glass ceramics increased firstly and then decreased with the increasing of the B2O3 content.The addition of reductant to the diopside glass inhibits the surface crystallization, and the crystallization process could be described by Diffusion-Limited Aggregation model.This work was supported by the Science and Technology Project of Hubei (20091g0041).更多还原