钆铝石榴石基新型高性能透明闪烁陶瓷的可控制备与性能研究

This project proposed doping of the Al and Gd sites of the main lattice of Gd3Al5O12 garnet with M1(2+)/M2(4+) pair (M1=Mg, Zn; M2=Si, Zr, Hf; M1/M2=1:1 molar ratio) and Ln3+ (Ln=Lu, Y, Tb), respectively, and based on which the development of high quality [(Gd1-xLnx)1-yCey]3[Al1-z(M1/M2)z]5O12 (x=0-0.5, y=0-0.02, and z=0-0.5) transparent ceramic scintillators. Apart from stabilization of the garnet lattice by the dopants, a concomitant control of the characteristics of the host lattice (macro-/micro-structure, bandgap structure, and crystal-field strength etc.) and the lowest lying 5d1 excited state of Ce3+ in the bandgap of the host will be achieved with the electronegativity and ionic radii of the Gd and Al sites for an optimized luminescence of Ce3+ ions. Meanwhile, the crucial issue of excited electron/host interaction, the key factors affecting Ce3+ luminescence, and also the underlying mechanisms will be clarified. Through mechanistic study and kinetics control of densification and microstructure evolution, high performance ceramic scintillators with inline transmittances reaching 80%, light output better than BGO single crystals, and dominant fluorescence lifetimes below 100ns will then be developed via vacuum sintering for medical imaging application.

提出采用等摩尔M1(2+)/M2(4+)和Ln3+分别掺杂Gd3Al5O12石榴石主晶格的Al位和Gd位（M1=Mg, Zn; M2=Si, Zr, Hf；Ln=Lu, Y, Tb）以研制[(Gd1-xLnx)1-yCey]3[Al1-z(M1/M2)z]5O12新型高性能透明闪烁陶瓷(x=0-0.5；y=0-0.02；z=0-0.5)。在掺杂稳定化石榴石晶格的同时，充分利用Gd、Al两格位的电负性和离子半径等因素协同调制基质特性（宏观/微观晶体构造、能带结构、晶体场强度等）和直接参与发光的Ce3+离子5d1最低激发态能级，实现发光/闪烁性能最优化。阐明跃迁电子与基质互作用和发光性能的关键影响因素及其作用机理等基础科学问题；明确烧结机理，有效控制烧结致密化和组织演化等动力学过程，真空烧结制备出透光率达约80%、发光性能优于BGO单晶、主光衰时间小于100纳秒的射线医学成像用透明闪烁陶瓷。

钆铝石榴石（Gd3Al5O12）是一类重要的光功能陶瓷材料，在闪烁和白光LED照明等领域具有良好的应用前景，但其在1200 °C以上的热分解严重妨碍了功能开发。本项目系统深入地探讨了Y3+、Lu3+、Tb3+稀土离子置换Gd3+以及等摩尔Mg2+/Si4+、Mg2+/Ge4+等置换Al3+对石榴石成相、晶体结构、局域配位、带隙能量和晶体场强度的作用，阐明了对Ce3+离子等发光性能以及陶瓷烧结致密化和显微组织的影响和内在作用机制。开发出了以饱和碳酸氢铵溶液为沉淀剂、通过冰水温度共沉淀制备高活性(Gd,Lu)AG:Ce石榴石纳米粉的新技术，并通过1700 °C真空烧结6 h得到了晶粒尺寸约8.7 μm、直线透过率达80%、450 nm蓝光激发下具有72.7%发光量子效率和50.4 ns荧光寿命的高性能陶瓷材料；研究了(Gd,Lu)AG:Ce微晶石榴石透明陶瓷的SPS烧结制备，明确了1300 °C下保温时间和后续退火对晶粒尺寸和光物性的影响，获得了透光率55~80%、晶粒尺寸仅约200~350 nm的透明陶瓷材料；开发出了以稀土层状氢氧化物单层纳米片为原料，在非晶Al2O3基板上经1450 °C原位反应烧结而制备高透明(Gd,Y)AG:Ce闪烁荧光膜的新技术，获得了晶粒尺寸约0.43 μm、厚约0.6μm、300~800 nm波段内透光率高达97%、460 nm 蓝光激发下发光的内量子效率约50%的膜材料；在铽铝石榴石（TbAG）中实现了Eu3+/Eu2+离子共掺杂，获得了多色发光并明确了发光机理；以Li-基石榴石（Li6CaLa2Nb5O12）为新型基质，通过Eu3+掺杂开发出了具有良好发光量子效率和热稳定性、可被蓝光和近紫外光激发的下转换红色发光荧光粉，并通过Yb3+/Er3+掺杂制备出了具有优异光学测温性能的上转换发光荧光粉。