稀土纳米结构SiO₂发光材料的制备及性能研究

【作者】 潘静；

【导师】 胡晓云；

【作者基本信息】 西北大学 ， 凝聚态物理， 2010， 硕士

【摘要】 本文采用溶胶-凝胶法和水热法制备了不同掺杂类型和不同结构的纳米Si02发光材料,通过荧光(PL)光谱、红外吸收谱(IR)、原子力显微镜(AFM)、透射电镜(TEM)等现代分析手段对样品进行了表征,并对其发光机理进行了分析。通过研究不同含水量、退火温度等因素对样品的荧光强度,磷光强度和发光寿命等性能的影响,得知无论对于粉末还是薄膜形态的Tb3+掺杂SiO2发光材料,这些因素同时影响着Tb3+的发光性能,且对发光强度的影响形成了一个竞争机制。经750℃退火处理样品的发光强度,随含水量的增加,先减弱后增强之后又减弱。通过分析样品的磷光特性,得知含水量对磷光与荧光强度的变化趋势一致,且对发光衰减时间也有明显的影响。最终,确定正硅酸乙酯,无水乙醇和蒸馏水的最优摩尔比为1：4：4,陈化时间为一天,在650-800℃存在最佳退火温度使得样品SiO2：Re3+发光最强。采用sol-gel法分别制备了Zn2+、Sn2+和Al3+等金属离子掺杂的SiO2：Re3+发光干凝胶和薄膜,薄膜分别镀在玻璃片和硅片上。充分利用F-7000荧光光谱仪分析了不同金属离子掺杂SiO2：Re3+样品的发光性能。通过掺杂金属离子改变稀土离子的微观环境使得样品SiO2：Re3+,Mn+发光效率增大。同等条件下,粉末发光最强,玻璃上镀的薄膜发光强度次之,硅片上镀的薄膜发光最弱。由于局域场增强或能量转移效应,金属离子掺杂SiO2：Re3+样品发光较不掺杂的强；金属离子掺杂样品所需的最佳退火温度比无掺杂样品的有所降低；不同类型金属离子掺杂SiO2：Re3+样品发光最强时对应的最佳浓度不同,如当Re是Tb时,Zn2+掺杂的最佳浓度为0.4%,而Sn2+为0.2%。此外,比较了利用水热法和溶胶凝胶法制备得到SiO2：Tb3+,Zn2+样品的发光性能,发现利用前者得到样品的发光不如后者的强,主要因为形成的基质网络结构不同。采用sol-gel法制备了核壳结构分别为SiO2：Tb3+包覆SiO2颗粒(Si@Si-Tb)和SiO2包覆SiO2：Tb3+颗粒(Si-Tb@Si)两种结构,通过改变纳米材料的结构使得样品发光效率增大。在一定条件下核壳结构的发光强度较粉末SiO2：Tb3+的强,且得出0.8 Si@Si-Tb-z样品发光效率最高,即核质量为0.8g的SiO2颗粒分散在25ml的SiO2：Tb3+溶液,未经陈化得到的样品发光效率高。随着核质量的增加,发光离子数也增加,发光增强,但增加到一定值时,发光减弱。通过分析过滤后所得澄清溶液和沉淀所得样品的发光性能,发现上清液所得产物均比下层沉淀的发光强,而与核质量或结构无关。更多还原

【Abstract】 SiO2 nano-meter luminescent materials with different types of doping or of different structure were prepared by the sol-gel and hydrothermal methods. The samples were characterized by Fluorescence Spectrum (PL), Fourier Transform Infrared Spectroscopy (FT-IR), Atomic Force Microscope (AFM) and Transmission Electron Microscope (TEM). And the luminous mechanism was studied in this paper.Through the research of different factors such as the molar ratio of H2O and annealing temperature to the fluorescence, phosphorescence intensity and phosphorescence lifetime of the sample, it showed that all the factors had influence on the luminous intensity of Tb3+doped SiO2 xerogels or films, and resulted a competitive mechanism. With the increasing amount of water, the luminous intensity of the samples annealed at 750℃first weakened, then enhanced and last weakened again. Through analyzing the phosphor properties of the samples, we found that the variation curves of the phosphorescence and luminescence intensity vs. the molar ratio of H2O showed the same trend. And the molar ratio of H2O also largely affects the decay time of the phosphorescence. Additionally, the optimum mole ratio of TEOS:ETOH:H2O is set as 1:4:4. The aging last one day, and the optimum annealing temperature at which the luminescent intensity of SiO2:Re3+samples are strongest existed in the extent from 650 to 800℃.SiO2:Re3+ luminescent xerogels and films doped Zn2+, Sn2+, Al3+ and other metal ions were prepared respectively by the sol-gel method, and the films were coated on the aerogel glasses or Si chips. The luminescent property of different metal ions doped SiO2:Re3+ samples with different forms were analyzed by making full use of the F-7000 fluorescence spectrometer. It was expected that the addition of metal ions can change the microcosmic environment of sample, as a result, the luminous efficiency of SiO2:Re3+, Mn+ would increase. Under the same conditions, the powder performed the strongest luminous intensity, followed by the film coated on glass as and Si substrate in turn. Due to the effect of local field increasing or energy transfer, the luminescent intensity of the metal ions doped SiO2:Re3+ samples were stronger than that of non-doped SiO2:Re3+ sample; the optimum annealing temperature also became lower; it corresponded to the different optimal concentrations of doped metal ions when the samples emitted the strongest light respectively, such as 0.4% for Zn2+, and 0.2% for Sn2+. In addition, the luminous intensity of the sample of SiO2:Tb3+, Zn2+ prepared through the hydrothermal method is weaker than that of the sample prepared by sol-gel preparation, mainly because of different formation of matrix network. In order to increase the luminous efficiency of rare earth doped SiO2 samples by changing the structure of nano-materials, two kinds of core-shell structures were introduced, including SiO2:Tb3+ coated SiO2 nano-spheres particles (Si@Si-Tb) and SiO2 coated SiO2:Tb3+ nano-spheres particles (Si-Tb@Si). Under a certain condition, the luminous intensity of core-shell structure was stronger than that of the powders, conclusively, the 0.8Si@Si-Tb-z sample reached the highest luminous intensity, which means that the production obtained from SiO2 nano-spheres with 0.8g nuclear quality scattering in the 25ml SiO2:Tb3+ solution without aging had a higher luminous efficiency. With the increasing of nuclear quality, numbers of ions also increased, leading to higher luminous intensity. However, the light began abating when the nuclear quality increased to a certain value, probably because the concentration quenching effect of the luminous ions happened. Through the analyzing the luminous property of the clarifying solution and the deposition samples after filtering, it showed that the luminous intensity of the products of the upper clarify solution are stronger than that of the precipitation no matter how much nuclear quality.更多还原