Pr:LuAG闪烁晶体的生长及光谱性能研究
文献类型：学位论文
| 作者 | 崔宏伟 |
| 学位类别 | 硕士 |
| 答辩日期 | 2012 |
| 授予单位 | 中国科学院上海光学精密机械研究所 |
| 导师 | 张龙 |
| 关键词 | 闪烁晶体 Pr:LuAG 晶体生长 分凝系数 光学性能 闪烁性能 |
| 其他题名 | Study on the growth and scintillation properties of Pr-doped Lu3Al5O12 crystals |
| 中文摘要 | 无机闪烁晶体是一种能将高能光子(X/γ射线)或高能粒子(质子、电子等)的能量转换成易于探测的紫外/可见光子的晶态能量转换体，在高能物理与核物理实验、影像核医学、工业在线检测以及安全稽查等领域有着广泛的应用情景。随着科学技术的迅猛发展，以NaI（TI）和BGO为代表的传统无机闪烁晶体已经不能完全满足不同应用对闪烁材料的苛刻要求。目前，在光输出和衰减时间性能方面结合较好的铈离子(Ce3+)掺杂材料是研究的热点，但人们仍然不断探索新的性能更加优异的闪烁材料。 在具有中等或较高晶体场强度的宽带隙晶态材料中，三价镨(Pr3+)离子具有更快的5d-4f能级发射，因此镨离子(Pr3+)掺杂的晶态材料引起人们越来越多的关注。稀土镨离子（Pr）掺杂的LuAG晶体（Pr:LuAG）就是一种性能优良的具有代表性的新型高温闪烁晶体，该晶体具有高光输出(20000Ph/MeV)、快时间衰减(20ns) 、大有效原子序数（Z＝62.9）和高密度（ρ＝6.73g/cm3）等特征。 由于Pr3+离子浓度、杂质离子以及生长条件等均对晶体性能产生较大影响, 本文用中频感应加热提拉法生长了系列掺杂浓度为 0.5at%、1at%、3at%的Pr:LuAG 闪烁晶体, 并系统研究了其光谱性能。 本论文开展的主要工作以及得到的主要结论如下： 第一，Pr:LuAG晶体的生长。改进和完善了提拉法生长Pr:LuAG晶体的工艺流程，通过下种、缩颈、放肩、等径和收尾等工序完成晶体生长，直径采用电子称控制，提拉速率为 1.1mm/h，晶体转速为16r/min，生长出了尺寸约为Φ（30-35）×（70-90）mm的晶体。晶体外形完整，呈淡绿色，无宏观缺陷，用激光束照射晶体，晶体内部未发现散射颗粒。 第二，Pr离子在LuAG晶体中的分布特征。分别取0.5at%，1at%和3at%三个浓度Pr:LuAG晶体的头部和尾部的样品研成粉末进行ICP-AES测试，Pr离子的分凝系数分别为：K0.005≈0.121，K0.01≈0.1468，K0.03≈0.1137。随着原始掺杂浓度的提高，晶体中Pr离子的浓度相应提高，掺杂质量较好，但3at%浓度时的分凝系数相比1at%时有一定的下降。 第三，系统研究了提拉法Pr:LuAG晶体的光谱和闪烁性能。透射光谱显示在183nm，240nm，285nm的位置有三个较强的吸收峰，而285nm处光吸收所引起的自吸收导致X射线激发时主峰310nm两侧的光谱区域呈不对称分布。在三种掺杂浓度中，3at%掺杂浓度的Pr:LuAG晶体有稍高的荧光强度，但光致激发峰位没有因掺杂浓度的不同而发生变化。对比发现光致激发发射主峰为329nm较X射线激发发射主峰310nm有一定的红移，可能与Pr离子的能带结构有关。 |
| 英文摘要 | Inorganic scintillation crystal is a kind of converter transforming the energy of high-energy photons (X-ray, γ-ray) or particles (proton, electron， etc) into UV/visible photons, which are easily detected. Comparison with traditional NaI(TI) and BGO scintillation crystals, Cerium doped high temperature oxide crystals possess the properties of high light yield and fast decay time. These crystals have been widely used in high-energy physics and nuclear physics experiments, nuclear imaging, industrial on-line detection, and security inspections, etc. Recently, cerium-doped high temperature inorganic scintillation crystals with high light output and fast decay time have attracted more and more interest of high-energy physicists and material scientists, which have become a hot research topic in these related fields. But people still continuously explore new scintillation materials for more excellent performance. In the wide band-gap materials become medium or high crystal field strength, the Pr3+ ion also shows fast 5d-4f emission, so Pr3+ doped amorphous materials aroused people more and more attention. Pr:LuAG, as a kind of excellent scintillator crystal with fast response time and high light yield, is mainly characterized by a high light output of 20000Ph/MeV, a short decay time constant of 20 ns, large effective atom number of 62.9, high density of ρ=6.73g/cm3. As Pr3 + ion concentration, impurities, ion and growth conditions can greatly affect the properties of crystal, we grew a series of Pr: LuAG scintillation crystals with the medium frequency induction heating method of doping concentration of 0.5 at % - 3 at % and studied the spectral properties of crystals in this paper. The main contents and conclusions of this thesis are described as following: The First, the growth of Pr: LuAG crystal. Improving and perfecting the process and technics of Pr: LuAG crystal growth by Czochralski method. The crystal growth is finished by descending seed, contracting neck, expanding shoulder, keeping diameter and bottoming up, etc. Crystal diameter is maintained with electro-balance. The pulling rate is about 1.1mm/h, and the rotating rate is about 16r/min; the typical size of crystal is Φ（30-35）×（70-90）mm. The crystals were complete shape, a light green and no macro defects. There are no scattering particles existed in crystals using the laser beam irradiation. The Second, Pr distribution characteristics in Pr:LuAG crystal were studied. The distribution characteristic was measured by using ICP-AES method with the head and the rear of the crystal with the doping concentration of 0.5at% ,1 at % and 3 at %. The detection results are: K0.005≈0.121，K0.01≈0.1468，K0.03≈0.1137. Along with the increase of the concentration of the original doping, the concentration of the ions Pr rise accordingly in the crystals, so the doping quality is good, but the segregation coefficient of 3at % doped Pr:LuAG declines slightly compared with that of 1at%. The Third, the optical properties and scintillation properties of the Pr:LuAG crystal. Transmission spectrum showed that there were three strong absorption peaks in the location of 183nm, 240nm and 285nm. And there was an asymmetrical distribution at 310nm on both sides of the spectrum owing to light self-absorption, which caused by the X-ray absorption at 285nm area. In these three doping concentration, 3at% doping concentration Pr:LuAG crystals had slightly higher fluorescence intensity, but the position of excitation peak did not change for different doping concentration. There is a certain red shift of fluorescence excitation peak at 329nm compared with the X-ray excitation peak at 310nm, which may be relevant to the energy level structure of Pr ion. |
| 语种 | 中文 |
| 源URL | [http://ir.siom.ac.cn/handle/181231/16717]  |
| 专题 | 上海光学精密机械研究所_学位论文 |
| 推荐引用方式 GB/T 7714 | 崔宏伟. Pr:LuAG闪烁晶体的生长及光谱性能研究[D]. 中国科学院上海光学精密机械研究所. 2012. |
入库方式： OAI收割
来源：上海光学精密机械研究所
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