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 　　  

Rare-earth incorporation in oxide scintillator crystals, glasses,
and nanostructures–Optical emission and beyond 

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

　           　Department of Materials Science, University of Milano-Bicocca, Milano (Italy) 

　　时间：11月6日 （周五）9:00 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: Anna Vedda is Professor of General Physics at the Department of Materials Science of the University of Milano-Bicocca. Her principal fields of interest are the functional properties of luminescent materials also at the nanoscale, with special emphasis on structure-property correlations. Her research is partly devoted to application-oriented topics. Significant results were obtained concerning scintillating fibers for medicine and high energy physics, fluoride and oxide nano-crystals for medical imaging, as well as silicon dioxide-based materials for micro- and opto-electronics. Her experimental activity includes radio- and photo-luminescence, wavelength resolved thermo-luminescence, optical absorption, impedance spectroscopy studies, micro-Raman scattering and infrared spectroscopy. She has presently useful international collaborations, namely with ETH Zurich, the Université Claude Bernard in Lyon, CERN, Czech Academy of Sciences, Universidad Autonoma in Madrid, and with Chinese Academy of Sciences. She is author of more than 200 papers in refereed journals and she is responsible of several domestic and European research projects. She is member of the scientific board of the Doctorate School in Materials Science and Nanotechnology of the University of Milano-Bicocca and of the European Physics and Chemistry of Advanced Materials European Doctorate (PCAM). 　　  

　　Abstract: Rare earth ions (RE) are characterized by a great variety of optical transitions that make them very attractive as luminescent activators in many optical applications including lighting devices, lasers, solar energy materials, and ionizing radiation sensors. Moreover, several insulating oxide materials are considered good hosts for RE ions. After doping, the RE energy levels can lie within the host band-gap and confer an optical activity to otherwise transparent systems.  

　　In this seminar it will be shown that, besides optical functionalization, RE incorporation in a host can simultaneously give rise to other modifications (thermodynamic, morphological, and structural) that can be controlled in order to engineer a material for a specific application. This is for example the case of mixed Lu_2xGd_2−2xSiO₅ scintillator crystals doped with Ce, in which the introduction of Gd causes a lowering of the melting temperature, a subsequent reduction of anion defects and a clear improvement of scintillator performances. In silica-based sol-gel glasses, RE incorporation allows to realize scintillating optical fibers. However at concentrations above 1 mol%, RE ions tend to aggregate in the form of crystalline or amorphous clusters. These nano-structures are mostly non luminescent. An exception is the case of Eu doped SiO₂ in which crystalline Eu₂Si₂O₇ pyrosilicate nanocrystals are formed and display a very high luminescence efficiency. Finally, incorporation of optically active RE (like Eu and Tb) above 5 mol%  in nano-crystalline Hafnia gives rise to intense luminescence emission together with the lattice simmetry modification from monoclinic to cubic, opening application perspectives to the material for the realization of nano-composites and ceramics.