基于晶体场和电-声作用设计的Ce3+/Eu2+掺杂的新体系潜在闪烁材料的合成和VUV/XEL光谱研究

Scintillators are key detecting materials for medical diagnosis (such as XCT-PET), high energy physics (such as synchrotron radiation, spallation neutron source), anti-terrorism, security screening and industrial non-destructive detection. The developments of new inorganic scintillators have been focused on rare earth ions doped materials at present, in which Ce3+/Eu2+ activated scintillators are particularly critical. On the basis of preliminary work, we will endeavor to understand the influences of following factors on 5d energies of Ce3+/Eu2+ ions in an exact host compound and luminescence of Ce3+/Eu2+ ions activated materials as well as their potential applications. These factors include the composition and the crystal structure, the stability, and the phonon frequency of the host compound, the site occupancy and the coordination polyhedron around the luminescent center, the Ce3+/Eu2+-O2- bond length, the coordination number and the site symmetry of Ce3+/Eu2+. Then we will design and prepare a series of silicates, (lithium-)borates and aluminates with ideal composition and structure as host compounds by taking into account these factors combined with the crystal field theory and electron-phonon coupling interaction. Through the investigations on the VUV-vis spectra, we will get insight into the relationship between the centroid, the crystal field splitting and the Stokes shift of Ce3+/Eu2+ 5d states in a specific lattice site of a definite host compound. In addition, we will study the dependencies of luminescence and its decay property on temperature and doping concentration. By the measurements of the X-ray excited luminescence (XEL) and in comparison with VUV-vis spectra, we will effort to understand the impact of different excitation conditions on luminescence of Ce3+/Eu2+ and energy transfer. Through these investigations, we aspire to find new potential scintillation materials.

闪烁材料是用于医学诊断(如XCT-PET)、高能物理(如同步辐射、散裂中子源)及反恐/防恐、安全检测和工业无损检测等领域的核心探测材料。稀土闪烁材料是目前无机闪烁材料发展的焦点，Ce3+/Eu2+是重要的激活离子。本项目在前期工作基础上，综合考虑基质化合物的组成和结构、稳定性、声子频率、发光中心格位占据及其对称性、配位多面体形式、键长、配位数等因素对Ce3+/Eu2+等稀土离子5d能级及其发光的潜在影响，结合晶体场理论，在认识电-声耦合作用的基础上，设计、合成具有理想组成和结构的系列硅酸盐、(锂)硼酸盐和铝酸盐等基质发光材料。通过VUV-vis光谱认识不同微环境下Ce3+/Eu2+的5d能级重心、晶体场劈裂和Stokes位移，分析温度和掺杂浓度对发光及其衰减特性的影响。研究X-射线激发下材料的发光性质，理解不同激发方式对发光和能量传递的影响，探索Ce3+/Eu2+离子激活的新体系闪烁材料。

项目紧扣申请书和计划书设定的目标实施，研究计划执行情况良好。在前期工作基础上，设计、合成了具有理想组成和结构的Ce3+/Eu2+激活的发光材料。通过真空紫外-可见(VUV-vis)光谱认识了不同微环境下Ce3+/Eu2+的5d能级重心、晶体场劈裂和Stokes位移，分析了温度和掺杂浓度对发光及其衰减特性的影响。研究了代表性样品在X-射线激发下材料的发光(XEL)性质，致力于探索Ce3+/Eu2+离子激活的新体系X-射线闪烁材料。此外，项目还发现了有潜在有用价值的高热稳定性红光发射材料、温度探测材料和光色可调的LED发光材料等。