Submitted on February 13, 2008
Accepted on March 11, 2008
High-Thermoelectric Performance of Nanostructured Bismuth Antimony Telluride Bulk Alloys
Bed Poudel 1
, Qing Hao 2, Yi Ma 1, Yucheng Lan 3, Austin Minnich 2, Bo Yu 3, Xiao Yan 3, Dezhi Wang 3, Andrew Muto 2, Daryoosh Vashaee 2, Xiaoyuan Chen 2, Junming Liu 4, Mildred S. Dresselhaus 5, Gang Chen 2*, Zhifeng Ren 3*
1 Department of Physics, Boston College, Chestnut Hill, MA 02467, USA.; GMZ Energy, Inc., 12A Hawthorn Street, Newton, MA 02458, USA.
2 Department of Mechanical Engineering, MIT, Cambridge, MA 02139, USA.
3 Department of Physics, Boston College, Chestnut Hill, MA 02467, USA.
4 Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, China.
5 Department of Physics and Department of Electrical Engineering and Computer Science, MIT, Cambridge, MA 02139, USA.
* To whom correspondence should be addressed.
Gang Chen , E-mail: gchen2{at}mit.edu
Zhifeng Ren , E-mail: renzh{at}bc.edu
These authors contributed equally to this work.
The dimensionless thermoelectric figure-of-merit (ZT) in bulk bismuth antimony telluride alloys has remained around 1 for more than 50 years. Here we show that a peak ZT of 1.4 at 100 °C can be achieved in p-type nanocrystalline bismuth antimony telluride bulk alloy. These nanocrystalline bulk materials were made by hot-pressing nanopowders ball-milled from crystalline ingots under inert conditions. Electrical transport measurements, coupled with microstructure studies and modeling, show that the ZT improvement is the result of low thermal conductivity caused by the increased phonon scattering by grain boundaries and defects. More importantly, ZT is about 1.2 at room temperature and 0.8 at 250°C, which makes these materials useful for cooling and power generation. Cooling devices that use these materials have produced high temperature differences of 86°, 106 °, and 119°C with hot-side temperatures set at 50°, 100°, and 150°C, respectively. This discovery sets the stage for use of a new nanocomposite approach in developing high performance low-cost bulk thermoelectric materials.
