低能量分辨率闪烁晶体CsBa2I5:Eu的制备及自吸收研究

The inorganic ionic crystals are the important materials for the nuclear detection. The lower energy resolution will lead to the more accurate nuclear detection. The academic circles tend to believe that the theoretical limitation of the energy resolution of the scintillation crystal at 662kev is 2%. Till now, there are three scintillation crystals approaching this theoretical limitation. They are respectively the LaBr3:Ce, SrI2:Eu and CsBa2I5:Eu crystal. The widely application of the LaBr3:Ce crystal and the SrI2:Eu crystal still faces many difficulties. The CsBa2I5:Eu crystal was found recently. But the CsBa2I5:Eu crystal shows very excellent scintillation properties and is promising for widely application. This project will grow the CsBa2I5:Eu crystal by Bridgman method and to obtain the high quality CsBa2I5:Eu single crystal with centimeter sizes. The light output, energy resolution, decay time and photoluminescence spectra of the CsBa2I5:Eu crystal will be measured. And the self-absorption of the CsBa2I5:Eu crystal will be studies. The main factors affecting the self-absorption of the CsBa2I5:Eu crystal will be identified. And the possible solution will be studied. And those studies will build a solid foundation for the application of the CsBa2I5:Eu crystal.

闪烁晶体是核辐射计量与探测的重要材料，晶体的能量分辨率越低，核辐射计量越准确。学术界倾向认为无机离子闪烁晶体能量分辨率在662keV处的理论极限值是2%，最接近这一极限值的晶体共有三个，分别为LaBr3:Ce晶体、SrI2:Eu晶体和CsBa2I5:Eu晶体，其中，LaBr3:Ce和SrI2:Eu晶体的大规模推广使用仍面临较大困难，CsBa2I5:Eu晶体相对发现较晚，却显示了优异的闪烁性能，应用前景巨大。本项目拟采用坩埚下降法生长CsBa2I5:Eu晶体，获得直径与长度均达到厘米级的CsBa2I5:Eu高质量单晶，通过测试CsBa2I5:Eu晶体的各项闪烁性能，具体包括光输出、能量分辨率、衰减时间和荧光光谱等，对目前最影响CsBa2I5:Eu晶体实用性的自吸收现象展开研究，指出影响CsBa2I5:Eu晶体自吸收的主要因素并提出可能的解决办法，为CsBa2I5:Eu晶体实用化奠定研究基础。

本项目用坩埚下降法生长了CsBa2I5:Eu、SrI2:Eu、KSr2I5:Eu、Cs4SrI6:Eu及Cs4SrI6:Eu:Sm掺Eu2+的闪烁晶体，通过研究组分配比以及生长工艺条件如温度梯度、下降速度等参数，获得了长、宽、高尺寸皆超过厘米的SrI2:Eu、KSr2I5:Eu、Cs4SrI6:Eu高质量单晶，通过测试多道能谱、荧光光谱等，研究了能量分辨率、衰减时间和自吸收等闪烁性能，其中10×10×10mm3的SrI2:Eu单晶在662keV（137Cs源）处的能量分辨率达5.5%，10×10×10 mm3的SrI2:Eu:Cs晶体的能量分辨率达5.4%，Cs4SrI6:Eu单晶尺寸达Ø2570mm3，15mm×15mm×2mm的Cs4SrI6:Eu晶体的能量分辨率为7%左右，用ICP测试了单根Cs4SrI6:Eu晶体中不同部位的Eu2+浓度，拟合得到Cs4SrI6:Eu晶体中Eu2+的分凝系数为1.13。SrI2:Eu和SrI2:Eu:Cs晶体在西北核技术所和成都理工大学得到了初步应用，为产品进一步推广打下了基础。在项目研究的同时发表了SCI等文章11篇，培养了4-6名研究生。项目组成员在此期间参加了一些专业领域的会议，宣传了上述成果。