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Low-dimensional thermoelectric alloy Ag_2Te Preparation and Properties of

Author: XiaoFeng
Tutor: ChenGang
School: Harbin Institute of Technology
Course: Chemical Engineering and Technology
Keywords: Thermoelectric materials Ag2Te Nanowires Solvothermal
CLC: TB34
Type: Master's thesis
Year: 2010
Downloads: 109
Quote: 0
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Abstract


Among the many thermoelectric materials, telluride thermoelectric material because of its high ZT value received widespread attention. Ag 2 Te thermoelectric materials is considered a highly promising material, while it has at 423 K from the low-temperature monoclinic phase β-Ag 2 Te into a high-temperature surface centered cubic phase α-Ag 2 Te shift characteristics, this feature will make the phase transition in the electrical properties of the material before and after the big change and make it achieve the \All along, Ag 2 Te thermoelectric materials such as complex preparation hampered its application, but how to improve the Ag 2 Te thermoelectric performance is also a difficulty. For the thermoelectric material, the preparation of low-dimensional materials can be effectively increased phonon scattering and reduced thermal conductivity, while giving the carrier transport channel and improved to provide a good electrical conductivity, but in the existing system to achieve thermal materials, nano is a huge challenge. In this paper, a step solvothermal method in ethylene glycol (EG) system was prepared with a diameter of approximately 300 nm of β-Ag 2 Te nanowires, which greatly simplifies the reported use of Ag Te Template Method 2 Te material, in order to further prepare Ag-Te system thermoelectric compounds and doping, composite and other technology foundation. By X-ray diffraction (XRD) characterized by its crystal structure, indicating that the Ag 2 Te crystal structure is monoclinic. Meanwhile, the use of thermal analysis (DSC, TG-DTA) and X-ray photoelectron spectroscopy (XPS) test, to determine its crystalline transition temperature, and surface composition. SEM, TEM and HRTEM tests show that by step Solvothermal get Ag 2 Te nanowires about 300 nm in diameter, while the length of more than 40μm. Conductivity tests show that the conductivity increases with increasing temperature, showing obvious semiconducting characteristics, and its conductivity at 700 K at up to 35 S cm -1 , and the Seebeck coefficient at 423 K tests show can reach its maximum value of about 70μV K-1, also discussed Ag 2 Te nanowires conductivity and Seebeck coefficient of the material effects. By adjusting the influence Ag 2 Te phase and morphology of process parameters, such as Ag / Te, NaOH, Na2EDTA and PVP, CTAB, SDS and PEG surfactants such as reaction temperature and other important process parameters, which determines prepared under the conditions of the existing pure phase Ag 2 Te nanowires key factor to further clarify the Ag , TeO 3 2 - of the reduction potential of the Chinese Communists in the solution process by reducing the impact of NaOH and Na2EDTA. Na2EDTA and Ag complex ions formed early in the reaction plays not only a stable Ag role of the crystal growth process is also played a release Ag to achieve the purpose of uniform growth. The most important by examining the morphology of the product increases with the reaction time and phase changes, a clear Ag 2 Te nanowire growth mechanism, the last of Ag 2 Te nm line morphology on thermoelectric properties of the material analyzed.

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