Experimental study of thermal conductivity reduction of silicon-germanium nanocomposite for thermoelastic application

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2005.Includes bibliographical references (p. 67-70).To improve the thermoelectric energy conversion efficiency of silicon germanium (SiGe), two methods were used to decrease the thermal conductivity by increasing phonon boundary scattering at interfaces. In the first method, SiGe alloys were annealed at a temperature higher than the melting point to increase the number of grain boundaries. In the second method, SiGe composites were made with nanosize silicon particles. For annealed SiGe alloys thermal conductivity decreased by a factor of two while power factor remained the same value. For SiGe nanocomposite thermal conductivity decreased by a factor of four to that of bulk alloy, but electrical conductivity deteriorated. Future work will focus on increasing electrical conductivity while reducing the thermal conductivity.by Hohyun Lee.S.M