SEMINAR 

Key Laboratory of Transparent Opto-fuctional Inorganic Materials,
Shanghai Institute of Ceramics, Chinese Academy of Sciences 

中国科学院上海硅酸盐研究所透明光功能无机材料重点实验室

Band gap and defect engineering strategies in the complex oxide scintillators optimization:
the differences for Ce and Pr-doping 

　　Speaker ：Prof. Martin Nikl  （中国科学院国际访问学者） 

　　           Institute of Physics AC CR, Cukrovarnicka 10, 16253 Prague, Czech Republic 　

时间：11月6日 （周五）10:15 AM 

地点：4号楼8楼会议室 

联系人：潘裕柏 研究员（2820） 

　　          李  江 研究员（2816） 　　  

　　Brief introduction: Martin Nikl graduated in 1981 at Faculty of Nuclear Science and Physical Engineering, Czech Technical University in Prague, and obtained his PhD. in 1986 in Institute of Physics, CAS. Currently serves as the department head and vice-director for targeted research in Institute of Physics, AS CR. His research interests include luminescence and scintillation mechanism in wide band-gap solids, energy transfer processes and role of material defects in them. He is the coordinator and participant in about 30 domestic and 10 international projects so far in the field of scintillation materials. Author and co-author of more than 600 papers in the refereed impacted international journals, 48 papers in non-impacted journals, six chapters in books and 49 papers in conference proceedings. Author and co-author of 38 invited keynote and plenary lectures at International Conferences. The publications received more than 6800 citations (Scopus, auto-citations excluded), Hirsch factor, H=49. He was an invited professor at (i) Institute for Materials Research, Tohoku University, Sendai, Japan, (ii) Universita di Milano-Bicocca, Milan, Italy and (iii) Shanghai Institute of Ceramics, CAS, Shanghai, China. 

　　Abstract: Single crystals of YAP:Ce, YAG:Ce and LSO:Ce were studied already in 1990’s and the latter found commercial application in PET, while the former two ones became widely used in various industrial and high-tech devices applications. Following the example of LSO, there was systematic effort in replacement of yttrium by lutetium also in YAP and YAG to increase the density and effective atomic number and to enable their use for gamma ray detection. In all three material families, solid solutions with suitable ratio of end compositions have shown some advantages in the manufacturing ease and/or scintillation parameters and LYSO:Ce, LuYAP:Ce and also LuYAG:Ce(Pr) became systematically investigated.  

　　Further development differentiated in these three groups of complex oxide scintillators. While R&D activity in perovskite family rather diminished, in the orthosilicate group the performance was further enhanced by divalent ion codoping and explained by the stabilization of Ce⁴⁺ center and its participation in scintillation mechanism. This strategy appeared successful also in case of aluminum garnets both in ceramic and single crystal forms. All these results can be understood as an output of defect engineering strategy which diminishes the effect of degrading electron traps. Even more complex solid solution approach in the garnet family came to discovery of new scintillator family, so called multicomponent garnets, in which the balanced Gd and Ga admixture into YAG:Ce (LuAG:Ce) host enhanced light yield almost three times close to 60 000 ph/MeV which is considered a theoretical limit in such oxide scintillators. These materials are thus the outcome of band gap engineering strategy, in which profound change in composition results in the changes of electronic band structure with positive effect in scintillation characteristics. 

　　This lecture will discuss the application of the above mentioned strategies in complex oxide scintillators of this kind, the underlying physical mechanism and possibilities for further material improvement.