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
Department of Chemistry and Waterloo Institute for Nanotechnology,
University of Waterloo, Ontario, Canada
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 Cu2–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 6th 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
1994 Ph. D. in Chemistry, University of Mainz, Germany
1991 M. Sc. in Chemistry, University of Münster, Germany
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