Enhanced thermoelectric properties in PbTe Nanocomposites
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1166-N03-27
Enhanced thermoelectric properties in PbTe nanocomposites H. Kirby,1 J. Martin,1 A. Datta,1 L. Chen,2 and G.S. Nolas1 1 2
Department of Physics, University of South Florida, Tampa, FL 33620 Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050, China
ABSTRACT Dimensional nanocomposites of PbTe with varying carrier concentrations were prepared from undoped and Ag doped PbTe nanocrystals synthesized utilizing an alkaline aqueous solutionphase reaction. The nanocrystals were densified by Spark Plasma Sintering (SPS) for room temperature resistivity, Hall, Seebeck coefficient measurements, and temperature dependent thermal conductivity measurements. The nanocomposites show an enhancement in the thermoelectric properties compared to bulk PbTe with similar carrier concentrations, thus demonstrating a promising approach for enhanced thermoelectric performance. INTRODUCTION Thermoelectric phenomena allow the solid-state interconversion of thermal to electrical energy, offering another route to provide a sustainable supply of energy for the world’s growing population. The effectiveness of a thermoelectric material is characterized by the thermoelectric figure of merit, ZT= S2T / ρκ, where S is the Seebeck coefficient, ρ is the electrical resistivity, T is the absolute temperature, and κ= κL + κe is the total thermal conductivity with κL as the lattice contribution and κe as the electronic contribution [1]. In recent years, both theoretical and experimental studies have strongly suggested that large improvements in ZT could be achieved in nanostructured systems [2]. At the same time thermoelectric devices necessitate materials in large quantities, and practical synthesis techniques are essential to incorporate nanoscale features within a bulk material. Currently, the most common top down approach is through ball-milling bulk powders into nano-scale grains [3-6]. However, as suggested in the work of Heremans et al. [4], this technique can cause strain within these materials that directly affects their transport properties in an unpredictable manner. A study by Heremans et al. [7] demonstrates how PbTe with small concentrations of Pb nanograins can be produced. This led to an adoption of solutionphase synthesis technique for PbTe nanocomposites, which may minimize the above mentioned issue and lead to higher thermoelectric performance than that of the bulk. This article reports a solution phase synthesis approach for preparing undoped as well as Ag doped PbTe nanocrystals that are then used to create bulk polycrystalline dimensional nanocomposites by spark plasma sintering (SPS). The Seebeck coefficient for the nanocomposites is larger than that of the bulk with similar carrier concentrations without a large increase in resistivity, thereby resulting in an enhanced thermoelectric figure of merit. EXPERIMENTAL DETAILS A low temperature reaction of a tellurium alkaline aqueous solution with a lead acetate trihydrate solution suitably precipitated out PbTe nanocrystals [8-9]. Various syntheses
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