SEMINAR 

The State Key Lab of 

High Performance Ceramics and Superfine Microstructure 

Shanghai Institute of Ceramics, Chinese Academy of Sciences 

中 国 科 学 院 上 海 硅 酸 盐 研 究 所 高 性 能 陶 瓷 和 超 微 结 构 国 家 重 点 实 验 室 

　　The Thermoelectric Energy Conversion: Copper Chalcogenides with extremely Low Thermal Conductivity and Magnesium Silicides with High Thermoelectric Performance
Holger Kleinke
Department of Chemistry and Waterloo Institute for Nanotechnology, 

University of Waterloo, Ontario, Canada  

　　时间：2016年10月31日（星期一）上午10: 00 

　　地点： 2号楼600会议室（国家重点实验室）　　  

　　欢迎广大科研人员和研究生参与讨论！ 

联系人：史  迅（2803） 

　　Abstract  

　　Thermoelectric materials can convert waste heat into electricity, and are thus of increasing importance in today's society, given the growing need for alternative energy sources. Many advanced thermoelectric materials are based on narrow gap semiconductors formed by heavily doped heavy metal chalcogenides including thallium, bismuth, and lead tellurides.  

　　An alternate route to low thermal conductivity may lie in cation mobility, such as mobile copper ions. This was demonstrated in case of Cu_2–xSe, which exhibits very low thermal conductivity, culminating in a high figure-of-merit zT value of 1.5 at 1000 K. The Cu ion conductivity, on the other hand, causes well-documented stability issues, inhibiting the use of this material in actual thermoelectric devices, as the ions move with the temperature gradient and/or the current. We have been investigating new barium copper chalcogenides for several years, aiming to find materials with localized Cu ion conductivity, where the 6^th period barium ions would impede the Cu paths as well as contribute to low thermal conductivity. Here, I will present the thermoelectric properties of two families of barium copper chalcogenides, both with low thermal conductivity and good thermoelectric performance. The stability under measurement conditions will be discussed in connection with the Cu diffusion paths.  

　　Problematic with the materials above are price and toxicity, in part but not exclusively caused by the incorporation of the scarce and toxic element tellurium. More sustainable materials exist, but until recently were not competitive with respect to the conversion efficiency. Variants of Mg₂Si were reported to exceed zT of unity around 800 K, when alloyed with germanium and/or tin, and doped with antimony or bismuth, and finally consolidated via spark-plasma-sintering. In this talk, I will present several such materials with a large compositional range that were simply prepared by hot-pressing. 　　  

　　Brief Introduction of Prof. Holger Kleinke 

　　Interim Executive Director of the Waterloo Institute for Nanotechnology 

　　Professor for Chemistry and Physics at Department of Chemistry and Waterloo Institute for Nanotechnology 

　　Education 

　　1994    Ph. D. in Chemistry, University of Mainz, Germany 

　　1991    M. Sc. in Chemistry, University of Münster, Germany 

　　Academic appointments 

　　2016-   Interim Executive Director, Waterloo Institute for Nanotechnology  

　　2000-   Assistant, Associate, and Full Professor of Chemistry, University of Waterloo 

　　1997-1999  Habilitant, University of Marburg, Germany 

　　1995-1997  Postdoctoral Researcher, Ames Laboratory, US-DOE 

　　Awards  and  Honors 

　　2002-2011  Canada Research Chair in Solid State Chemistry (Tier 2) 

　　2000   Premier's Research Excellence Award 

　　1997-1999  Liebig Fellow, University of Marburg, Germany