稀土离子掺杂玻璃的闪烁发光机理研究

Scintillator is a kind of materials that absorbs the high-energy photos or particles (X-rays, gamma rays) and then emits ultraviolet and visible light. In contrast to single-crystal scintillators, scintillators based on glass matrices have many attractive features, such as ease of manufacture in different sizes and shapes, moderate costs, good optics uniformity, isotropy and suitability for the industrialization production. Scintillating glasses can make up the deficiencies of single-crystal scintillators. In spite of these advantages, scintillating glasses develop slowly over the past decades due to low light yield and density, namely, the density of scintillating glasses with high light yield is too low, and the light yield of scintillating glasses with high density is not good..On the other hand, in most of the papers in the area of scintillating glass,the researchers neglected the particularity of the scintillation emission at present, and they used the photoluminescence to replace the scintillation emission. There are few papers for researching on the light yield. Then this situation result in a consequence that we are unable to choose the glass composition accurately and impede the developing of scintillating glass. Our experimental results showed that there is not a one-to-one correspondence between photoluminescence intensity and scintillation emission intensity in the same glass. For example, the Ce3+ doped phosphate glass has very strong photoluminescence in intensity; however, its light yield of scintillation is very low. There is not a theory or mechanism model to explain this phenomenon now. This project will research the effecting law of glass composition on the light yield of scintillation for the rare-earth ions doped glasses and then explore the mechanism of specific correlation between the glass structure and scintillating properties, as well as the scintillation emission mechanism of scintillating glasses. It will establish a foundation for further improving the scintillation properties and practical application of scintillation glasses by accomplishing the project.

闪烁体是一种能将高能光子或粒子的能量转化成紫外-可见光的发光材料。闪烁玻璃具有制备容易、成本低、光学均匀性好、各向同性、成型加工方便、适合于批量和大尺寸工业化生产等优点，可弥补闪烁晶体的不足。但目前闪烁玻璃存在的问题是光产额高于BGO晶体的玻璃密度低，而高密度玻璃的光产额低。目前国内外发表的论文中大多数都是采用光致发光性能来代替闪烁发光，对光产额的研究非常少，忽视了闪烁发光的特殊性。这使得在玻璃成分的选择上存在着盲目性，阻碍着闪烁玻璃的发展。我们的研究结果显示光致发光与闪烁发光性能并没有一一对应的关系，如Ce3+离子在磷酸盐玻璃中有很强的光致发光，但其光产额很低，目前尚没有什么理论和模型能解释这个现象。本项目就是要通过研究稀土离子掺杂玻璃的组成和制备工艺条件对闪烁光产额的影响规律，探讨玻璃结构和闪烁性能的内在相关性，揭示其闪烁发光机理，为进一步提高闪烁玻璃的性能并使其实用化奠定良好的基础。

低成本、大尺寸、光学均匀性好、可成光纤的闪烁玻璃在大型强子对撞机等核物理、核医疗等有着潜在的应用。研究玻璃的闪烁发光机理是发展闪烁玻璃的关键科学问题。本课题采用双坩埚石墨还原法、在玻璃原料中添加NH4NO3、NH4F、尿素、金属原料粉等多种方法制备了各种发光活性离子（Ce3+、Pr3+、Tb3+、Yb2+、Eu2+、Sn2+）掺杂的高硅氧玻璃和SiO2 (P2O5) -B2O3-Al2O3-Gd2O3系统高Gd2O3玻璃，并拓展到氟化物玻璃、氟氧玻璃和微晶玻璃。建立了一套以X-射线为激发源的闪烁性能测试系统，并对其密度、光谱性能和闪烁发光等基本性能和玻璃的结构和缺陷进行了测试，在此基础上探讨了玻璃的闪烁机理。实现了预定的专利申请和论文发表数，完成了项目的研究计划。获得的新颖结果如下：.1．将电荷迁移淬灭效应模型引入玻璃中，有效地解释了为什么多年来人们发现Ce离子掺杂的低密度玻璃有高的发光量子效率，而高密度的玻璃其发光量子效率很低的原因。分析磷酸盐、含ZnO和碱金属离子玻璃的闪烁性能后认为玻璃中可变价态、具有半导体性质和玻璃修饰体化合物不会影响光致发光性能，但会破坏闪烁发光性能。.2. 首次报道了在X射线激发下，Yb2+离子掺杂石英玻璃表现出中心波长在525 nm的发射带。.3. 伴随着辐照，玻璃结构中的羟基含量会变化，高羟基时羟基含量会降低，低羟基时羟基含量会上升。.4. Ce3+, Eu2+和Eu3+共存的玻璃中，在X射线的激发下，由于Ce3+→Eu3+和Eu2+→Eu3+能量传递，光致发光的蓝光转变为Eu3+的红色发光。声子边带谱分析结果显示还原后玻璃中Si形成体附近的Eu3+全部被还原为Eu2+，B和Al形成体周围的Eu3+部分被还原为Eu2+。.5. 通过热处理成功制备了Pr3+掺杂、晶相为β-BaZrF6的氟锆酸盐微晶透明玻璃，其光致和辐照发光强度是基质玻璃的2.5-3倍。.6. 铈掺杂的氟磷酸玻璃，经过高于玻璃转变温度的热处理后，XRD以及拉曼和红外光谱都显示玻璃的内部结构未改变，也没有宏观分相，但玻璃的光致发光和闪烁发光都大幅度的提高。闪烁效率达到了BGO 的35%。 . 目前闪烁玻璃的现状是低密度的玻璃闪烁光产额高，但高密度的玻璃产额低；与晶体材料相比，还存在能量分辨率低和耐辐射硬度差的问题。我们认为玻璃微晶化是最有效解决这些问题的最佳方法。