掺铈GSO和GYSO闪烁晶体生长及其特性研究
文献类型：学位论文
| 作者 | 介明印 |
| 学位类别 | 硕士 |
| 答辩日期 | 2005 |
| 授予单位 | 中国科学院上海光学精密机械研究所 |
| 导师 | 徐军 |
| 关键词 | 闪烁晶体 晶体生长 分凝系数 光学性能和闪烁性能 |
| 其他题名 | Study on the growth and properties of inorganic scintillators Ce-doped GSO and GYSO |
| 中文摘要 | 无机闪烁晶体是一种能将高能光子（X/T射线）或粒子（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、医疗、安检、工业等领域有着广泛的应用。特别是近年来，随着科学技术的发展对闪烁材料的性能提出了更高的要求，尤其是具有高光输出快衰减的硅酸盐闪烁晶体成为人们研究的热点。稀土饰离子（ce）掺杂的GdZsi05晶体（ce：Gso）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（8000Ph/MeV、快时间衰减（6ons）·大有效原子序数（Z：59）和高密度（p＝6．7g/cm3)等特征，同时与其他闪烁晶体相比，ce：Gso晶体有两个显著的特点就是在高温下光输出仍很稳定，抗辐照能力强也是目前已知晶体中最好的。本论文主要以ce：Gso和ce：GYso高温闪烁晶体为研究对象，从以下几个方面展开工作：第一，Ce：GSO晶体生长。改进和完善了提拉法生长Ce:GS0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1-5mm/h，晶体转速10-40/min；剖析了Ce：GSO晶体的开裂原因，通过温场调节和工艺控制，成功解决了GSO晶体的开裂问题，现在能生长出。70mm的优质透明不开裂的Ce：GSO晶体，其成品率显著提高。第二，饰离子在GSO晶体中的分布特征。利用ICP-AES和傅立叶红外等技术系统研究了Ce：GSQ高温闪烁晶体中Ce的分凝系数和浓度分布特征。在0．lmol％一o．smol％浓度范围内，Ce离子的分凝系数为0．58一0．78，熔体中Ce浓度越大，分凝系数越小；在轴向上，Ce浓度从晶体头部到尾部逐渐增大；在径向上，Ce浓度分布比较均匀。第三，Ce：GSO晶体的光谱和闪烁性能。室温下Ce：GSO晶体吸收谱显示：在200一60Onln波段Ce和Gd吸收峰共有9个，且随Ce浓度增加，Ce的吸收峰增强，Gd的吸收峰相对较弱；Ce：GSO晶体光致荧光主峰位为436lun，能与PMT有效匹配；Ce：GSO晶体光致荧光有浓度碎灭效应，在0．lmol％一0．8mol％范围内，因同核能量传递，造成Ce浓度越高，光致发光效率越低；XEL发射光谱显示：其XEL发射峰位未变，仍为436nm；Ce：GSO晶体空气退火和氮气退火不同程度的提高xEL强度，前者可以解释为氧空位的减少，后者可归因于ce3＋的增多；0．lmol％一0．smolo／0范围内，未退火的Ce：GSO晶体的光输出为2000Pe/Mev，超过日本Hitachi的标准样品（1500Pe/Mev），考虑退火因素，我们认为经过退火处理的Ce：GSO晶体光输出将会更强，这还需进一步的实验验证。第四，ce：GYso晶体的生长和光谱性能。首次系统研究了。：GYSO晶体的生长和光学性能，发现Y元素的引入一定程度上克服了GSO晶体的解理开裂问题。XRD和ICP数据分析显示，当Y组分小于等于2Omol％时，GYSO晶体和GSO晶体的物相、晶胞参数及Ce离子的分凝特征基本一致。5mol％一20mol％浓度范围内，Ce：GYSO晶体可见光（＞40OIun）透过率提高6％，其光致荧光积分强度较Ce：GSO晶体提高100％，这表明Ce：GYSO晶体将可能比Ce：GSO闪烁晶体有更优良的闪烁性能，这有待进一步的实验和研究。 |
| 英文摘要 | A scintillation material is a kind of converter transforming the energy of high-energy photons (X-ray, Y -ray) or particles (proton, electron etc) into UV/visible photons, which are easily detected. It has wide applications for radiation detection in different fields such as high energy physics, nuclear physics, nuclear medical diagnostics and industrial measuring systems. In recent years, the development of scientific research has required scintillation materials with improved properties and much effort has been focused on materials with fast respone time and high light yield. Cerium-doped gadolinium orthosilicate, Ce:GSO, as a kind of excellent scintillator crystal with fast respone time and high light yield, is mainly characterized by a high light output of 8000Ph/MeV, a short decay time constant of 60 ns, large effective atom number of 59, high density of P =6.71g/cm3; In comparison with other scintillation crystals, Ce:GSO scintillator show special characteristics in following two respects: one is that the light yield of Ce:GSO crystal keeps constant even at high temperature (nearly 200°C), the other is that Ce:GSO shows excellent radiation resistant. In this paper, we focuse mostly on the high-temperature scintillators of Ce:GSO and Ce:GYSO crystals, and carry on studies about works as listed below. The First, the growth of Ce:GSO crystal. Improving and perfecting the processand technics of Ce:GSO crystal growth by Czochralski method. The boule growth is finished by descending seed, contracting neck, expanding shoulder, keeping diameter and bottoming up, et.al. Crystal diameter is maintained with electro-balance, pulling rate is about l-5mm/h, rotating rate is about 10-40r/min; Analysing the cause of Ce:GSO crystal cracking, and resolving successfully the cracking problem of Ce:GSO crystal by adjusting temperature grade and technics controlling. Now the high-quality and transparent Ce:GSO crystal with 70mm diameters can be grown successfully, rate of finished products has been improved remarkably. The Second, Ce distribution characteristics in Ce:GSO crystal, by using ICP-AES and Fourierism infrared technics, we have systematically investigated Ce distribution coeffcient and characteristics in Ce.GSO crystal, which shows that Ce distribution coefficient is about 0.58-0.78 when Ce concentration is between 0.1mol% and 0.8mol%. The larger Ce melting concentration is, the smaller Ce distribution coefficient is; Ce concentration becomes larger gradually along crystal axis from the top to the bottom of the GSO boules, while the cerium distriburtion radically uniformity along the diameter of CerGSO boules. The Third, the optical properties and scintillation properties of the CerGSO crystal. The absorption spectrum shows that there are nine absorption bands between 200nm and 600nm at room temperature. The intensity of Ce absorption peak becomes stronger, that of Gd absorption peak submerged by stronger Ce absorption bands when the Ce melting concentration is larger. The peak value of photon-luminescence is 436nm, which is matched effectively with sensitive receiving range of PMT. The photon-luminescence of Ce:GSO shows concentration quenching effect, that is, the lower the photon-luminescence efficiency of Ce:GSO is, the higher Ce concentration is in the range of 0.1mol%-0.8mol% Ce concentrations because the same particle energy transferring. The XEL spectrum of Ce:GSO shows that the emission peak of Ce:GSO is 436nm,as the same as the photon-luminescence peak of Ce:GSO. The XEL intensity of Ce:GSO under Air or flowing H2 atmosphere annealing can increases respectively in different extent. The increasing XEL intensity of Ce.GSO could be due to the reducing of the oxygen vacancy number after air atmosphere annealing, or the increasing of the Ce3+ ion number after flowing H2 atmosphere. The light output of the unannealed Ce:GSO crystal is 2000 Pe/MeV for Ce concentration in the range of 0.1mol%-0.8mol%. It exceeds the standard sample of Japan Hitachi Co. Ltd, of which the light output is 1500Pe/MeV. The Fourth, the crystal growth and optical properties of Ce:GYSO. For the first time, we have systematically investigated the crystal growth and optical properties of Ce:GYSO. We have overcome the cracking problem of Ce:GSO in some extent by doping yttrium element into Ce:GSO. XRD and ICP experiment data show that the GYSO crystal is content with GSO in structure phase, crystal cell parameters and Ce distribution. Optical transmission of Ce:GYSO improves by 6% in the wavelength range larger than 400nm, and the integral intensity of photon-luminescence of Ce:GYSO increases by about 100%. All these excellent properties of Ce:GYSO indicate the scintillation properties of Ce:GYSO should be more excellent than that of Ce:GSO, which needs to be measured and investigated. |
| 语种 | 中文 |
| 源URL | [http://ir.siom.ac.cn/handle/181231/16610]  |
| 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 | 介明印. 掺铈GSO和GYSO闪烁晶体生长及其特性研究[D]. 中国科学院上海光学精密机械研究所. 2005. |
入库方式： OAI收割
来源：上海光学精密机械研究所
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