Nanocomposite of Bi 2 Te 3 with Metal Inclusions for Advanced Thermoelectric Applications
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1218-Z05-11
Nanocomposite of Bi2Te3 with Metal Inclusions for Advanced Thermoelectric Applications Sumithra Santhanam,1 Nathan J.Takas,1 Dinesh K.Misra,1 Pierre F.P.Poudeu1,2 and Kevin L.Stokes1,3 1 Advanced Materials Research Institute, University of New Orleans, New Orleans, LA 70148. 2 Department of Chemistry, University of New Orleans, New Orleans, LA 70148. 3 Department of Physics, University of New Orleans, New Orleans, LA 70148. ABSTRACT Recent experimental and theoretical studies have shown that the thermal to electrical power conversion efficiency (as measured by the thermoelectric figure of merit) can be enhanced in nanocomposite materials. Primarily, these efforts to improve the thermoelectric efficiency rely on reducing the lattice thermal conductivity through nanostructuring of the materials or the introduction of a second nanometer-scale phase into the composite material. Here, we show that the inclusion of semimetal nanoparticles into bismuth telluride (Bi2Te3) can result in both an increase in the electronic transport properties (so called "power factor") as well as a decrease in lattice thermal conductivity. The effect of different volume fractions of Bi nanoinclusions (3% and 5%) on the thermal and electrical properties of the composite are reported. A marginal increase in the thermoelectric figure of merit is achieved for 3% metal nanoinclusion, whereas a significant improvement in the figure of merit could be achieved for 5% nanoinclusions in the Bi2Te3 thermoelectric matrix. INTRODUCTION Thermoelectric devices can directly convert thermal to electrical power. These devices can help growing demand for environmentally benign power generation for both the small scale (waste heat recovery) and large scale power generation. The efficiency of thermoelectric devices depends on the material parameters; electrical conductivity (σ), Seebeck coefficient (S) and thermal conductivity (K) which are used to define the dimensionless thermoelectric figure of merit (ZT) as S2σT/K, where T is the absolute temperature and K=Kelectronic+Klattice contains both the electronic and lattice components of the thermal conductivity. To achieve a high ZT, the material should possess a high electrical conductivity (σ), high Seebeck (S) and low thermal conductivity (K). However, this is difficult due to the interdependence of these transport parameters. For example, Seebeck coefficient scales inversely with the electrical conductivity as known from the Mott equation while Kelectronic varies proportionally to σ [1]. Presently, for applications near room temperature the commercial modules are based on Bi2Te3 alloys with optimized carrier concentration. Tuned Bi2Te3 has a high electrical conductivity σ~1000Ω-1cm-1 and high Seebeck coefficient~200µV/K at room temperature (RT) resulting in a power factor on the order of 40 µW/cmK2 [1]. The thermal conductivity, K, at RT is 1.9 W/m-K resulting in a ZT close to unity. However, the conversion efficiency of modules based on these optimized materials is still very small (~10%). Hence f
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