1 Impact of YSZ Nanoinclusions on the Thermal Conductivity of n-type Si 80 Ge 20 Alloys Prepared by Spark Plasma Sintering Ali Lahwal 1* , S. Bhattacharya 1 , Jian He 1 , Di Wu 2 , A. Peterson 2 , S. J. Poon 2 , L. Williams 3 , A. Mehdizadeh Dehkordi 4 , T. M Tritt 1,4* 1 Department of Physics and Astronomy, Clemson University, Clemson, SC 29634-0978 2 Department of Physics, University of Virginia, Charlottesville, VA 3 NanoSonic Corporation, Blacksburg, VA 4 Department of Materials Science and Engineering, Clemson University, Clemson, SC 29634-0978 Abstract Nanocomposites have become a new paradigm for thermoelectric research in recent years and have resulted in the reduction of thermal conductivity via the nano-inclusion and grain boundary scattering. In this work we report the preparation and thermoelectric study of SiGe-YSZ nanocomposites prepared by Spark Plasma Sintering (SPS). We experimentally investigated the reduction of lattice thermal conductivity (κ L ) in the temperature range (30-800K) of n-type Si 80 Ge 20 P 2 alloys with the incorporation of Yttria Stabilized Zirconia (YSZ) nanoparticles (20 ~ 40 nm diameter) into the Si-Ge matrix. These samples synthesized by using the SPS technique were found to have densities > 95% of the theoretical density. The thermal conductivity, at both low and high temperatures, was measured by steady state and laser flash techniques respectively. At room temperature, we observed approximately a 50% reduction in the lattice thermal conductivity as result of adding 10% YSZ by volume to the Si 80 Ge 20 P 2 host matrix. A phenomenological model developed by Callaway was used to corroborate both the temperature