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铽铝石榴石基新型陶瓷闪烁粉体的制备及性能表征

发布时间:2018-04-17 00:36  文章来源:笔耕文化传播

  本文选题:Tb_3Al_5O_(12)(TAG) + 溶胶-凝胶法 ; 参考:《西南科技大学》2017年硕士论文


【摘要】:铽铝石榴石基(Tb_3Al_5O_(12),TAG)陶瓷闪烁体具有密度较高,抗辐射性能良好,光输出高,衰退时间短等优点,有望应用于高能物理、核医学、地质勘探以及安检等领域。TAG闪烁单晶存在生长条件苛刻、制备周期长、生产设备要求高、成本高、尺寸受限以及离子掺杂不均匀等问题,使得其应用受到限制。因此,研究和制备TAG多晶陶瓷闪烁体具有重大意义。作为制备TAG多晶陶瓷闪烁体的第一步,TAG粉体必须具有高纯度、良好的分散性、均匀性以及良好的烧结活性。当前TAG粉体的制备普遍存在粉体分散性差、粒径不均一、活化能垒高等不足,导致了其烧结活性低、烧结温度高、荧光强度低等缺陷,对于后续的制备带来了限制。此外,对于TAG粉体制备的具体反应历程也缺乏探究。因此,为了降低TAG粉体的烧结温度,本论文首先选取了两种反应条件最为温和的TAG粉体制备方法:共沉淀法与溶胶-凝胶法,成功制备出TAG粉体并对其微观结构及相关性能进行了表征。发现溶胶-凝胶法制备的前驱体,TAG相的结晶温度可降低到920°C远低于共沉淀法(1000°C),最终荧光强度也高出共沉淀法约30%。由此可见,溶胶-凝胶法在TAG粉体制备方面更具有优势。进一步从原子扩散速率角度出发,通过优化溶胶-凝胶法制备TAG粉体的工艺参数,调节络合剂柠檬酸的量改善粉体的微观结构,为原子的短程扩散提供通道,提高了其原子扩散速率,有利于各相的晶化,从而降低其烧结温度。在柠檬酸的摩尔量与金属离子总的摩尔量的比例为1:1的情况下,制得的TAG粉体分散性、均匀性最为优异,带来了良好的烧结活性,与第一章制备参数相比,TAG晶相的结晶温度降低到了877.5℃,荧光强度提高了约32%;同时,对溶胶-凝胶法制备TAG粉体的具体反应历程进行了探究。在此基础上,又从各相成核的活化能垒角度出发,通过引入金属离子降低各相成核的活化能垒,从而进一步降低了TAG粉体的烧结温度。本研究工作首次将Fe~(3+)离子引入TAG体系,发现其能够成为优先成核位点从而降低各相成核的活化能垒,进一步提高TAG粉体的烧结活性。在其最优组成Tb_3(Al_(0.95),Fe_(0.05))_5O_(12)条件下,TAG相的结晶温度可降低到780℃,但是Fe~(3+)离子的引入一定程度上降低了TAG体系的荧光强度。因此,为弥补Fe~(3+)离子掺杂带来的不足,利用Ce~(3+)振动强度大等优点,采用Fe~(3+)、Ce~(3+)两种离子的共掺杂的方法制备了一种新型陶瓷闪烁粉体,与第一章制备参数相比,在其最优组成Tb_(2.97)(Al_(0.95)Fe_(0.05))_5O_(12):Ce_(0.03)条件下保证其良好烧结活性的同时荧光强度提高了1倍。
[Abstract]:Terbium aluminum-garnet based scintillator Tbs3Al5OK12Tago ceramic scintillator is expected to be used in high energy physics and nuclear medicine because of its high density, good radiation resistance, high light output and short decay time.The application of tag scintillation single crystal in geological exploration and security inspection is limited due to its harsh growth conditions, long preparation period, high production equipment, high cost, limited size and uneven ion doping.Therefore, it is of great significance to study and prepare TAG polycrystalline ceramic scintillators.As the first step to prepare TAG polycrystalline ceramic scintillator, tag powder must have high purity, good dispersion, uniformity and good sintering activity.At present, the preparation of TAG powders has many defects, such as poor dispersion, uneven particle size, low activation energy barrier, low sintering activity, high sintering temperature and low fluorescence intensity.In addition, the specific reaction process of TAG powder preparation is also lack of exploration.Therefore, in order to reduce the sintering temperature of TAG powders, two preparation methods of TAG powders with the most mild reaction conditions, coprecipitation method and sol-gel method, were first selected in this paper.TAG powder was successfully prepared and its microstructure and related properties were characterized.It is found that the crystallization temperature of the precursor (tag) phase prepared by sol-gel method can be reduced to 920 掳C much lower than that of the coprecipitation method (1000 掳C), and the final fluorescence intensity is about 30% higher than that of the co-precipitation method.Therefore, the sol-gel method has more advantages in the preparation of TAG powders.From the angle of atomic diffusion rate, the technological parameters of preparing TAG powder by sol-gel method were optimized to improve the microstructure of the powder by adjusting the amount of citric acid, which provided a channel for the short-range diffusion of atoms.The atomic diffusion rate is increased, and the crystallization of each phase is favorable, thus lowering the sintering temperature.When the molar ratio of citric acid to metal ions is 1:1, the TAG powder has the most excellent dispersity and uniformity, and it has good sintering activity.Compared with the preparation parameters in the first chapter, the crystallization temperature of the crystal phase of tag is reduced to 877.5 鈩,

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