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Study on Synthesis and Properties of Bi2Te3-Sb2Te3 Based Nano-Composite Thermomaterials

Author: ChenWeiTao
Tutor: ZhouYuXiang
School: Harbin Institute of Technology
Course: Chemical Engineering and Technology
Keywords: Thermoelectric materials Hydrothermal method Bi2Te3-Sb2Te3 Secondary hydrothermal Nano - core-shell structure
CLC: TB383.1
Type: Master's thesis
Year: 2009
Downloads: 77
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Abstract


The thermoelectric material is a kind of functional materials for the direct conversion of heat and electricity can be, and has important applications in thermoelectric cooling and thermoelectric power generation. The traditional Bi 2 Te 3 -based alloy thermoelectric figure of merit ZT around 1, is a better performance near room temperature thermoelectric materials. In recent years, many scholars turned to for better performance Bi 2 the Te 3 -Sb 2 Te 3 based nanocomposite thermoelectric materials and the Sb 2 the Te 3 single-phase alloys. The first step in water (solvent) thermal synthesis of Bi 2 Te 3 and the Sb 2 Te 3 single phase, then in the ternary alloy composite, try the Sb 2 the Te 3 -Bi 2 Te 3 -based materials, the secondary (two-step) hydrothermal synthesis experiments; step mixed Hydrothermal Method a BixSb2-xTe3 ternary alloy; to Bi 2 Te prepared by physical mixing 3 / Sb 2 Te 3 ternary composites and test its electrical properties. N2H4 · H2O as reductant Bi 2 Te 3 single-phase powder synthesized under hydrothermal conditions with solvent the heat (ethanol) conditions, respectively. SEM analysis showed that the product of the latter environment is more uniform, but the size of particles is relatively large. Electric properties testing showed that the synthesized samples are n-type semiconductor, although the conductivity of the sample in the latter environment is less than 1/8 of the former, but the Seebeck coefficient than the former is significantly higher, reaching-98μV / K, this is mainly due to sample microscopic morphology and content of impurities Te caused. 240 ° C and 48h under hydrothermal conditions synthesized pure phase of Sb 2 Te 3 hexagonal piece. Studies have shown that the reaction time, the concentration of alkali the direct impact the Sb 2 Te 3 purity followed morphology; temperature Sb 2 Te 3 hexagonal chip thickness important impact; different Te sources will lead to the Sb 2 Te 3 changes in wafer form, size, and mainly due to the mechanism of nucleation different result caused by differences in the nuclei number; surfactants EDTA-2Na the crystal becomes more lenient mainly depends on the ligand itself and Sb3 role PVP by changing the hydrothermal environment lead to product a large number of non- Rules Sb 2 Te 3 massive grain exists. First K (SbO) C4H4O6, Te powder as raw material, N2H4 · H2O as the reducing agent, the hydrothermal synthesis Fu Te Sb 2 Te 3 x precursor powders then as a raw material and then join Bi (NO3) 3.5 H2O, the second hydrothermal synthesis, end up with a part of the core-shell structure Sb 2 Te 3 - Te (Bi 2 3 ) x / 3 nanocomposites. The XRD tests show excessive Te has got to maximize the use of the second step hydrothermal synthesis process. SEM and EDAX analysis showed that Sb 2 Te 3 - (Bi 2 Te 3 ) x / 3 has been initially has a part of the nano-core-shell cladding structure. Electrical performance tests show that it is this not completely coated interface exists, such that the Seebeck coefficient of the material at room temperature compared the pure Sb , Te , 2 3 about 60μV / K .

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