Enhanced Thermoelectric Capability in Silicon Germanium Bulk Alloys
31 October 2008
Researchers at Boston College and MIT report achieving a dimensionless thermoelectric figure-of-merit (ZT) of 0.95 in p-type nanostructured bulk silicon germanium (SiGe) alloys—about 90% higher than what is currently used in space flight missions, and 50% higher than the reported record in p-type SiGe alloys.
These nanostructured bulk materials were made by using a direct current-induced hot press of mechanically alloyed nanopowders that were initially synthesized by ball milling of commercial grade Si and Ge chunks with boron powder.
They attribute the enhancement of ZT to a large reduction of thermal conductivity caused by the increased phonon scattering at the grain boundaries of the nanostructures combined with an increased power factor at high temperatures.
Resources
Giri Joshi, Hohyun Lee, Yucheng Lan, Xiaowei Wang, Gaohua Zhu, Dezhi Wang, Ryan W. Gould, Diana C. Cuff, Ming Y. Tang, Mildred S. Dresselhaus, Gang Chen, and Zhifeng Ren (2008) Enhanced Thermoelectric Capability in Bulk Silicon Germanium (SiGe) Alloys. ASAP Nano Lett., doi: 10.1021/nl8026795
It would be better for many readers if the efficiency of thermoelectric conversion devices is expressed in terms of
a percentage of the Carnot Cycle !!
Posted by: Jorge | 31 October 2008 at 06:30 PM