稀土掺杂钇铝石榴石陶瓷与粉体的显微结构调控及其光学性能研究

发布时间：2018-05-20 01:10

本文选题：YAG陶瓷 + 助烧剂　；参考：《山东大学》2017年博士论文

【摘要】：钇铝石榴石(Y_3Al_5O_12,YAG)是一种重要的功能性材料,在民用领域拥有非常广泛的应用,在国防科技领域占据非常重要的地位。作为激光增益介质,掺杂Nd~(3+)离子YAG透明激光陶瓷的很多性能优于Nd:YAG激光晶体,是高功率激光器重要备选材料。并且,稀土离子掺杂YAG荧光粉,可用于LED光源照明。光的高透过率是实现Nd:YAG陶瓷激光性能的基本条件。而陶瓷的显微结构,特别是晶粒尺寸、晶界结构和气孔是影响陶瓷透明度最根本因素。在激光陶瓷制备过程中,除了纳米粉体的形貌、尺寸以及烧结工艺对陶瓷显微结构具有重要影响之外,在原料中添加助烧剂可以实现对显微结构调控。尽管大量文献对助烧剂对透明激光陶瓷的结构与性能的影响进行了研究,但对于两种助烧剂协同作用的研究较少。稀土掺杂YAG纳米荧光粉体的尺寸、形貌和结晶程度直接影响其荧光性能。固相烧结法合成的粉体结晶性好,荧光量子效率高,但因为颗粒大,荧光粉应用困难;液相纳米合成法合成的粉体颗粒尺寸小,但其结晶度差,荧光效率低。现有纳米粉体制备技术无法实现纯度高、形貌和粒径可控、结晶性高、分散性好的纳米荧光粉体。因此,本论文研究以稀土掺杂YAG材料为主要研究对象,通过对YAG材料制备技术的研究,实现Nd:YAG透明激光陶瓷的显微结构调控和YAG:Ce纳米棒的可控制备。本论文主要研究工作和结论如下:1.正硅酸乙酯(TEOS)和柠檬酸镁(MC)的协同作用对Nd:YAG透明陶瓷微观结构的调控和性能提升(1)在Nd:YAG透明陶瓷制备过程中添加TEOS和MC作为助烧剂,调节其添加比例,实现对陶瓷晶粒大小、粒度分布和晶胞参数等微观结构调控。在TEOS与MC合理配比下,使其产生协同作用,促进微缺陷排除和烧结周期优化,使透明陶瓷的透过率提高并产出高功率激光。在Nd~(3+)掺杂量为2 at.%的YAG透明陶瓷中添加TEOS与MC配比为2:1的助烧剂,可以得到晶粒尺寸适中且粒径分布集中、无气孔、无杂相、晶格结构平衡稳定的透明陶瓷。共掺7.5 wt.%a TEOS与3.75 wt.‰MC的2 at.%Nd:YAG透明陶瓷是最优样品,光学透过率在1064 nm波长处为83.7%,在400 nm波长处为79.2%,并且其具有0.3 W的低激光输出阈值,在约8.5 W功率808 nm波长泵浦光下输出功率超过2 W的1064 nm激光,其激光输出斜效率为25.2%。(2)研究不同配比助烧剂,样品微观结构和透明陶瓷性能之间的关系,并给出助烧剂协同作用的机理。TEOS和MC助烧剂对陶瓷微观结构的作用实质是Si~(4+)和Mg~(2+)离子对Nd:YAG中Al~(3+)的取代。这种取代促进陶瓷致密化进程,同时协调陶瓷晶粒大小。然而,Si~(4+)、Mg~(2+)和Al~(3+)的离子半径不一样并且价态也有差别,这导致阳离子和氧离子空位及电荷的不平衡,并导致晶格微畸变和晶格结构的不稳定。在定量情况下,适当调节Si~(4+)和Mg~(2+)的比例,可以使电荷相互补偿、空位相互抵消、消除不平衡状态,最终获得优异的Nd:YAG陶瓷。复合助烧剂的合理使用、协同作用和作用机理研究,为透明陶瓷性能提升和量化制备提供了思路。2.YAG纳米粉体的可控制备及其核-壳结构前驱体形成机理的研究(1)以Al_2O_3纳米粉为模板和Al源,Y~(3+)溶液为Y源,尿素(Urea)为沉淀剂,采用半液相法制备具有Al_2O_3/Y-compound核-壳结构的YAG纳米前驱体,经过煅烧制得尺寸均匀、成分单一、结晶性良好、分散性极佳、烧结活性好的球形YAG纳米粉体。并由此粉体烧结得到YAG透明陶瓷。通过XRD、SEM、TEM和FTIR等表征测试手段证实Al_2O_3/Y-compound核-壳结构及其演变过程。(2)通过添加表面活性剂和调节反应的沉淀速度,改变YAG前驱体的制备条件,讨论核-壳结构前驱体的形成机理。在反应体系中,当在A1_2O_3纳米颗粒上引入表面活性剂后,使其表面带负电荷,而Y-compound沉淀微核表面也带负电荷,由于静电排斥,Y-compound将无法组装包覆在Al_2O_3纳米颗粒上。而在没有表面活性剂的反应体系中,Al_2O_3纳米颗粒表面带正电荷,在静电吸引的作用下Y-compound将预包覆Al_2O_3纳米颗粒。所以静电作用是核-壳结构形成的一个驱动力。采用NH_4HCO_3代替尿素作为沉淀剂来减缓反应的沉淀速度。NH_4HC0_3的顺序滴加有利于Y-compound沉淀微核自组装并逐步长大成纳米颗粒,Y-compound沉淀与Al_2O_3纳米颗粒分离,将不会形成核-壳结构。而尿素在反应之前要在反应体系中充分溶解均匀,待体系达到其分解条件时(温度达到83℃以上),尿素会瞬间完全分解出大量负离子基团(HCO_3-、OH-等),这些负离子基团在整个反应体系内与Y~(3+)结合生成过饱和量的Y-compound微核(爆发成核过程)。"爆发成核"得到的前驱体纳米颗粒的高表面能是Al_2O_3/Y-compound核壳结构形成的驱动力。这种半液相法制备核-壳结构前驱体的方法和机理,可以用于其它二元氧化物纳米粉体的可控制备。3.半液相法制备纳米棒状YAG:Ce荧光粉及其机理研究与应用(1)首次以半液相法为主要制备方法合成一维纳米棒状YAG:Ce荧光粉。采用水热法调控合成一维棒状NH_4Al(OH)_2CO_3并通过煅烧得到结晶性和分散性良好的纳米棒状Al_2O_3颗粒。以纳米棒状Al_2O_3颗粒为模板和A1源,Y~(3+)溶液为Y源,尿素为沉淀剂,采用半液相法制备具有核-壳结构的纳米棒状YAG前驱体,经煅烧得到直径为250-400 nm长度为3-5 μm的纳米棒状YAG:Ce荧光粉。所制备的纳米棒状荧光粉分散性好,结晶性高,具有相对大的比表面积和非常少的表面缺陷。采用XRD、SEM、TEM等表征测试手段揭示纳米棒状荧光粉的形成过程和成型机理。(2)一维纳米棒状YAG:Ce荧光粉的荧光性能优于相同Ce~(3+)掺杂量的纳米球状YAG:Ce荧光粉。纳米棒状YAG:2at.%Ce~(3+)荧光粉的荧光量子产率(QY)为40.12%。虽然纳米棒状荧光粉的比表面积比纳米球状荧光粉的比表面积小,但是纳米棒状荧光粉的结晶性好,表面缺陷少,这是其荧光强度高的原因。并且,由于其特殊的棒状结构,纳米棒状荧光粉具有两个荧光寿命,一个对应其本体特征的长寿命和一个对应其缺陷特征的短寿命。用纳米棒状YAG:Ce荧光粉标记骨髓间充质干细胞,表现出良好的生物相容性和荧光稳定性。开拓了 YAG:Ce荧光粉的应用领域,显示其重要的应用价值。
[Abstract]:Y_3Al_5O_12 (YAG) is an important functional material. It has a very wide application in the civil field and occupies a very important position in the field of Defense Science and technology. As a laser gain medium, the doping of Nd~ (3+) ion YAG transparent laser ceramics is better than the Nd:YAG laser crystal. It is an important material for high power lasers. In addition, the rare earth ions doped YAG phosphors can be used to illuminate the LED light source. The high transmittance of the light is the basic condition for realizing the performance of the Nd:YAG ceramic laser. The microstructure of the ceramics, especially the grain size, the grain boundary structure and the porosity, is the most fundamental factor affecting the transparency of the ceramics. In the preparation of the laser ceramics, the shape of the nanometer powder is in addition to the shape of the nanometer powder. The appearance, size and sintering process have important effects on the microstructure of ceramics, and the addition of burning AIDS in the raw materials can control the microstructure. Although a large number of literatures have studied the influence of the burning AIDS on the structure and properties of transparent laser ceramics, few studies have been made on the synergistic effect of the two kinds of combustion aids. Rare earth doped YAG nano The size, morphology and crystallinity of the rice phosphor directly affect the fluorescence properties of the powder. The powders synthesized by the solid phase sintering method have good crystallinity and high fluorescence quantum efficiency, but because of the large particles and the difficulty in the application of phosphor powders, the particle size of the powders synthesized by the liquid phase nano synthesis method is small, but its crystallinity is poor and the fluorescence efficiency is low. It is impossible to realize nanofluorescence powders with high purity, controllable morphology and particle size, high crystallinity and good dispersivity. Therefore, this thesis focuses on the study of rare earth doped YAG materials. Through the research on the preparation technology of YAG materials, the microstructure and control of Nd:YAG transparent laser ceramics and the controllable preparation of YAG:Ce nanorods are realized. The research work and conclusion are as follows: 1. the synergistic effect of TEOS and MC on the microstructure of Nd:YAG transparent ceramics is regulated and improved (1) adding TEOS and MC as a burning aids to the preparation of Nd:YAG transparent ceramics, and adjusting the proportion of its addition to the grain size, particle size distribution and cell parameters of the ceramics. Structure regulation. Under the reasonable ratio of TEOS and MC, it can produce synergistic effect, promote the removal of micro defects and optimize the sintering period, improve the transmittance of the transparent ceramics and produce high power laser. In the YAG transparent ceramics with Nd~ (3+) doping amount of 2 at.%, the proportion of TEOS and MC is 2:1, and the grain size is moderate and the particle size can be obtained. A transparent ceramic with a concentration, no pores, no heterozygosity and a stable and stable lattice structure. The best sample is mixed with 7.5 wt.%a TEOS and 3.75 wt. per 1000 MC. The optical transmittance is 83.7% at the 1064 nm wavelength and 79.2% at the 400 nm wavelength, and it has a low laser output threshold of 0.3 W, at about 8.5 W power 808 nm wavelength pump. The output power of 1064 nm laser with output power of more than 2 W is 25.2%. (2), the relationship between the microstructure of the sample and the properties of the transparent ceramics is studied. The mechanism of the synergism of the CO combustion agent,.TEOS and the effect of MC on the microstructure of ceramics is the essence of Si~ (4+) and Mg~ (2+) ions to Al~ in Nd:YAG. Instead of 3+, this substitution promotes the process of ceramic densification and coordinates the size of the ceramic grains. However, the ionic radius of Si~ (4+), Mg~ (2+) and Al~ (3+) is different and the valence state is different, which leads to the imbalance of the vacancy and charge of the cation and oxygen ions, and leads to the lattice micro distortion and the instability of the lattice structure. When the ratio of Si~ (4+) and Mg~ (2+) is adjusted, the charge can be compensated each other, the vacancy counteracts each other, and the unbalance state is eliminated. Finally, the excellent Nd:YAG ceramics are obtained. The rational use of the compound sintering aids, the synergism and the mechanism of action are studied. The control of the.2.YAG nano powder is provided for the improvement of the performance of the transparent ceramics and the preparation of the quantitative preparation of the.2.YAG. Study on the formation mechanism of the precursor of its core shell structure (1) using Al_2O_3 nanometer powder as template and Al source, Y~ (3+) solution as Y source and urea (Urea) as precipitant, the YAG nano precursor with Al_2O_3/Y-compound nuclear shell structure was prepared by semi liquid phase method. After calcining, the scale is uniform, the composition is single, crystallization is good, dispersion is excellent, sintering live. Good spherical YAG nano powder. And the powder is sintered to get YAG transparent ceramics. The nucleation and shell structure and evolution process of Al_2O_3/Y-compound are confirmed by XRD, SEM, TEM and FTIR. (2) the preparation conditions of the precursor of YAG are changed by adding the surface active agent and the precipitation rate of the reaction, and the precursor of the nuclear shell structure is discussed. In the reaction system, when the surface active agent is introduced on the A1_2O_3 nanoparticles, the surface is negatively charged, and the Y-compound precipitated micronucleus surface is negatively charged. Because of electrostatic exclusion, Y-compound will not be coated on the Al_2O_3 nanoparticles. In the reaction system without surfactant, Al_2O_3 nanoscale will be in the reaction system. The particle surface has positive charge and the Y-compound will be precoated with Al_2O_3 nanoparticles under the action of electrostatic attraction. So the electrostatic action is a driving force of the nucleation and shell structure. The sequential addition of NH_4HCO_3 instead of urea as a precipitator to slow down the precipitation rate.NH_4HC0_3 is advantageous to Y-compound precipitation micronucleus self assembly and gradually longer. Dacheng nanoparticles, the separation of Y-compound precipitation and Al_2O_3 nanoparticles, will not form a nuclear shell structure, and urea will be fully dissolved in the reaction system before the reaction. When the system reaches its decomposition conditions (the temperature is above 83 degrees C), the urea will completely decompose a large number of negative ions (HCO_3-, OH-, etc.), these negative ions. The group is combined with Y~ (3+) in the whole reaction system to produce Y-compound micronucleus (nucleation process). The high surface energy of the precursor nanoparticles is the driving force of the Al_2O_3/Y-compound nuclear shell structure. The method and mechanism of the semi liquid phase method to prepare the core shell precursor can be used in other parts. Study and application of nano rod like YAG:Ce phosphor prepared by.3. semi liquid phase preparation by.3. semi liquid phase method and its mechanism study and application (1) one dimensional nano rod like YAG:Ce phosphor was synthesized by semi liquid phase method for the first time. The one-dimensional bar like NH_4Al (OH) _2CO_3 was synthesized by hydrothermal method and the crystallization and dispersion were obtained by calcining. Good nano rod like Al_2O_3 particles were used as the template and A1 source, Y~ (3+) solution as Y source and urea as precipitator. The nano rod like YAG precursor with nuclear shell structure was prepared by semi liquid phase method. The nanometer rod like YAG:Ce fluorescent powder with a diameter of 250-400 nm with a diameter of 3-5 micron was calcined. The nano rod like fluorine was prepared. The light powder has good dispersibility, high crystallinity, relatively large specific surface area and very few surface defects. The forming process and forming mechanism of nano rod like phosphor are revealed by XRD, SEM, TEM and other characterization tests. (2) the fluorescence properties of one dimensional nanoscale YAG:Ce phosphor are superior to that of the same Ce~ (3+) doped nanoscale YAG:Ce phosphor. The fluorescence quantum yield (QY) of the rice rod like YAG:2at.%Ce~ (3+) phosphor is 40.12%., although the specific surface area of the nano rod like phosphor is smaller than that of the nanoscale phosphor, but the crystallinity of the nano rod like phosphor is good and the surface defect is few. This is the reason for its high fluorescence intensity. And, because of its special bar like structure, nanoscale rod like structure. The phosphor has two fluorescence lifetimes, a long life corresponding to its noumenal characteristics and a short lifetime corresponding to its defect characteristics. The labeling of bone marrow mesenchymal stem cells with nano rod like YAG:Ce phosphor shows good biocompatibility and fluorescence stability. The application field of YAG:Ce phosphor has been opened up and its important application price is shown. Value.
【学位授予单位】：山东大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TQ174.1

【参考文献】