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1044-U01-05

Synthesis and Thermoelectric Properties of Lead Chalcogenide Nanocomposites Joshua Martin1, Stevce Stefanoski1, Li Wang2, Lidong Chen2, and George S. Nolas1 1 Department of Physics, University of South Florida, 4202 E. Fowler Ave., PHY 207, Tampa, FL, 33620 2 State Key Laboratory of High Performance Ceramics and Superfine Microstructures, Shanghai Institute of Ceramics, Dingxi Road 1295, Chinese Academy of Sciences, Shanghai, 200050, China, People's Republic of ABSTRACT Doped lead telluride dimensional nanocomposites were prepared by densifying nanocrystals synthesized employing an alkaline aqueous solution-phase reaction. The nanocrystal synthesis procedure resulted in high product yields of over 2 g per batch. These nanocrystals were then subjected to Spark Plasma Sintering (SPS) for densification. Transport properties were evaluated through temperature dependent resistivity, Hall, Seebeck coefficient, and thermal conductivity measurements. The results for these lead telluride nanocomposites were compared to bulk polycrystalline lead tellurides with similar carrier concentrations. INTRODUCTION Thermoelectric effects enable the solid-state inter-conversion of heat and electricity. The thermoelectric figure of merit, ZT=S2σT/κ, defines the effectiveness of a thermoelectric material, where S is the Seebeck coefficient, σ is the electrical conductivity, T is the absolute temperature, and κ is the total thermal conductivity [1]. Recent progress in a number of higher efficiency thermoelectric materials (room temperature ZT > 1) can be attributed to the nanoscale enhancement these specific material properties. Many of these materials demonstrate increased Seebeck coefficient and decreased thermal conductivity due to the phenomenological properties of nanometer length scales. As an initial exploration, Hicks and co-workers investigated the effect of a onedimensional quantum wire structure on the thermoelectric figure of merit [2]. Their calculations demonstrated the significant enhancement potential of these nanostructures when compared to bulk values. This work encouraged experimental research using thin films, heterostructures, nanowires, and other nanostructures. For example, p-type Bi2Te3/Sb2Te3 10 Å/50 Å supperlattice structures demonstrated a room temperature ZT = 2.4, with a thermal conductivity reduced by a factor of 2 compared to other Bi2Te3 alloys [3]. Harman and co-workers reported a room temperature ZT = 1.6 in PbTe/PbTeSe quantum-dot superlattices (QDSLs) that contain PbTeSe nanodots imbedded in a PbTe matrix [4]. Kong and co-workers reported an enhancement in Si/Ge supperlattices [5]. Recently, Heremans and co-workers reported an increased Seebeck coefficient for PbTe with the inclusion of Pb precipitate nanostructures [6]. Crystals of AgmPbmSbTem+2n with self-formed nanoscale grains of PbTe also demonstrate a large figure of merit [7,8]. Another method to incorporate nanoscale dimensions into bulk materials is through ballmilling [9,10]. This procedure rapidly grinds powders to sub-micron dime