【作者】 阿木日沙那；

【导师】 杨桦；

【作者基本信息】 吉林大学 ， 物理化学， 2008， 博士

【摘要】 随着场发射（ FED）和等离子体（ PDP）发光显示技术的发展,对荧光粉的粒度分布大小、稳定性、发光效率、发光亮度以及导电性等提出了更高的要求,由于纳米发光材料显示了许多奇特的性能,因而它极有希望成为下一代的新型发光材料。在众多纳米发光材料中,以稀土钒酸盐为基质的发光材料具有良好的化学稳定性和热稳定性,但对其荧光性能的研究相对较少,因而对其产生了浓厚的研究兴趣。本文综述了纳米发光材料的研究现状,系统介绍了镧系离子的光谱理论及镧系掺杂发光纳米微粒的研究背景,概括和评述了近年来镧系掺杂发光纳米微粒的合成和表面修饰所取得的进展和面临的问题,并对其今后的研究方向进行了总结和展望。在此基础上,我们针对场发射显示器（FED）和等离子平板显示器（PDP）对发光材料的要求,以稀土钒酸盐纳米发光材料作为研究对象,采用柠檬酸溶胶-凝胶法和水热合成法,成功制备了多种具有不同光学性质的稀土钒酸盐纳米晶。应用X射线衍射（XRD）、场发射扫描电镜（SEM）、透射电镜（TEM）、光致发光谱（PL）、傅立叶变换红外光谱（FT-IR）、热分析（DTA-TG）、PL光谱、发光衰减曲线和寿命等手段研究了合成条件和掺杂离子浓度等对稀土钒酸盐纳米微粒的晶体结构、形貌和尺寸、表面化学性质、掺杂离子的固溶度和掺杂格位以及发光性能的影响和控制规律,取得了一系列重要的结论和创新性成果,为稀土钒酸盐纳米发光材料成为一种极具发展前景的新型发光材料打下了坚实的基础。采用简单易行的柠檬酸溶胶-凝胶法成功地制备了核-壳结构的SiO₂@YVO₄:Eu荧光体粉体。包覆后的样品不仅保持了核SiO₂的球形形貌又具有纯YVO₄:Eu的发光特性。制备的壳层致密均匀、光滑、无开裂,厚度可以控制在50-100 nm。此外,首次利用水热合成法在玻璃底片上外延生长了YVO₄:Eu的微米棒晶阵列和分等级结构样品。更多还原

【Abstract】 With the technical development of FED and PDP, the requirement which includes the crystal size distribution, stability, luminescence efficiency, brightness and conductivity of the powder also has been improved. Since the luminescent nanomaterials have many unique functions, thus it is highly hoped that they will be a new type of luminescent material of next generation. Among the large number of luminescent nanomaterials, rare-earth vanadate host luminescent nanomaterials have a good chemical and thermal stability, but there are few investigations focused on the luminescent properties of rare-earth vanadate luminescent nanomaterials. In this thesis, we synthesized rare-earth vanadate luminescent nanomaterials through many different ways, and systematically investigated the luminescent properties to find new types of high-performance luminescent materials.（1） In the first chapter, we briefly describe the state of art of the research on luminescent nanomaterials; systematically introduce the spectrum theory of lanthanide ions and the research background of lanthanide-ions-doped luminescent nanomaterials; besides that, we generalize and review the improvement in the synthesis and surface modification of rare-earth-ions-doped luminescent nanomaterials in recent years, as well as the problems which confronts; moreover, the possible research directions in future are also summarized and predicted.（2） The synthesis method and condition of rare-earth-based luminescent nanomaterials powder have been studied in this paper. Eventually, under a determined optimum research condition, we synthesized a series of nano-scale YVO4:RE3+ （RE = Eu, Dy, Sm）, Y1-xRExVO4:Eu3+ （RE = La, Gd）, using citric acid as complexing agent, through the improved complexing-sol-gel method. The nanoparticles we synthesized have a uniform size, the scale of which is below 100 nm, and the smallest one can be as large as 20 nm. Under the UV irradiation, we studied the luminescent properties of the powder by the numbers. The result of the research indicates that the luminous intensity of nanoparticles increases with increasing the annealing temperature. Furthermore, as an appropriate amount of La³⁺ and Gd³⁺ doped into YVO4 host, the luminous intensity is also improved as a result of the distortions of crystal structure. （3） 4F9/2 - 6H13/2 transition of Dy3+ in YVO4:Dy3+ belongs to electric dipole transitions （?J = 2）, which can be easily influenced by the surroundings. Besides that, YVO4 has the same crystal structure as YPO4, thus YVO4 and YPO4 can easily form solid solutions. Based on the reasons discussed above, we successfully synthesized YPxV1-xO4:Dy3+ luminescent nanoparticles by citric acid sol-gel method. The luminescent nanoparticles we got are close to sphere and have a sharp size distribution. After the relationship between the molar ratio of V/P in YPxV1-xO4:Dy3+ and the color of nanoparticles under the irradiation of UV was studied by the numbers, we found that with the decline of V/P molar ratio, the color gradually changes from yellow to blue. And in the range that X=0.775-0.85, the emission color is white. YPxV1-xO4:Dy3+, therefore, can be a new type of white-emission material. However, as a material to put into practical applications, some of its performances such as brightness still need to be improved.（4） Luminescent powder of SiO2@YVO4:Eu3+ core-shell structure was successfully synthesized by simple citric acid sol-gel method. Through controlling the condition of solution concentration, the mass ratio of core/shell, the annealing temperature, and the thickness of shell, we found out the most suitable coating condition. The samples we obtained not only keep the sphericity of SiO2 core but also have the radiation characteristic of pure YVO4:Eu3+. The shell we prepared is tight, uniform, smooth texture, and has no crack, the thickness of which can be controlled within 50-100 nm. Moreover, under 800 oC, YVO4:Eu3+ can crystallize well on the surface of SiO2, which greatly reduce the reaction temperature. The characterization results which are used to explain the formation mechanism of core-shell structure indicate that the hydroxyl on the surface of SiO2 and the viscosity of precursor solution play a crucial role. The emission lifetime of Eu3+ ions and PL emission intensity were both increased with increasing annealing temperature and the thickness of the shell. As the mass ratio of core/shell increases to 60%, the emission intensity of SiO2@YVO4:Eu3+ core-shell structure reaches to 91% of that of pure YVO4:Eu3+.（5） We respectively synthesized high-quality YVO4:Eu3+ micro-rod crystal array and flower structure crystal on the underlay of amorphous glass, using Na2H2L·2H2O to complex metal ions, through hydrothermal method, and we did not use any surfactant and template. Micro-rod crystal array epitaxially grew on the glass substrate which was covered with YVO4:Eu3+ crystal-seed layer under low temperature and using sol-gel method. Meanwhile, flower structure grew on glass substrate which did not have crystal seed. Through SEM, we observed that high-quality and large area of YVO4:Eu3+ micro-rods were perpendicularly grown on the substrate. The lengths of the micro-rods are roughly the same, and they have a tight and uniform distribution and the length of every micro-rod was approximately 4μm. The cross section of micro-rod was an obvious rectangle and the size of it was in the range from 300×300 nm2 500×800 nm2. The flower structure was composed of many rectangle micro-rods which radiate to all direction. Every single rod had rectangle cross-section and definitive crystal facet. Moreover, we discussed the growth mechanism of micro-rods in the solution of this system and also pointed out its impact on the morphology. Based on the growth mechanism we studied the cause of formation, which provides a possible technical approach to form YVO4:Eu3+ micro-rods of different morphology and optimize them. The result indicates that YVO4:Eu3+ micro-rods with different morphology all belong to zircon structure, whose a-axis is the optimum orientation of these deposited YVO4:Eu crystals.（6） We synthesized REMAl3O7（RE = Gd, La; M = Ca, Sr） luminescent nanomaterials through citric acid sol-gel method, and used XRD, AFM, SEM, TEM and PL to characterize the nanoparticles. The characterization result indicates that single-crystal luminescent nanoparticles are engendered under 800 oC annealing. The nanoparticles have sphericity morphology, the mean size is less than 100 nm, and with the rise of annealing temperature the crystal becomes more perfect and the size of nanoparticles also increases. Compared with solid-state reaction at high temperature, the annealing temperature declines by 600 oC . Under the irradiation of UV, the example radiates intensive red and green light, which respectively accord to the 5D0– 7F2 transition of Eu3+ and the 5D4–7F5 transition of Tb3+. Besides that, the emission intensity also increases with the increasing annealing temperature and the amount of Eu3+ ions （or Tb3+） doped in the host.更多还原