Please use this identifier to cite or link to this item: http://hdl.handle.net/11455/9904
標題: Thermoelectric and Microstructure properties of Bismuth Telluride by MOC-HP
熱壓對鉍碲熱電材料特性與微結構之影響
作者: 曾逸婷
Tseng, Yi Ting
關鍵字: thermoelectric;熱電;bismuth telluride;hot pressuring;Metal organo complexes;microstructure;鉍化碲;熱壓;金屬有機合成;微結構
出版社: 材料工程學研究所
摘要: 
本研究是以金屬有機化合成Bi2Te3粉末在不同參數(溫度與壓力)下熱壓製備Bi2Te3合金。分別利用熱電測量系統、X光繞射儀、場發射掃描電子顯微鏡、X光能譜儀、微硬度試驗機等量測合金熱電性質晶體結構微結構成分以及硬度等性質,探討改變不同熱壓條件對Bi2Te3熱電性質微結構與成分的影響。
熱電量測系統測量的結果,以熱電力而言,熱電力最佳值出現,在熱壓溫度320℃與壓力220MPa,其值為-155(μ•V/ K)。基本上電阻率隨著溫度與壓力增加電阻率下降,電阻率最好值出現,在熱壓溫度380℃與壓力260MPa時,其值為2.7×10-3(ohm-cm)。功率因子最大值為6.1(W/cm.K2),其熱電力為-130(μv / K),電阻率為2.8× 10-3(ohm-cm)由最大值得知,熱壓後的試片電阻率的影響大於熱電力。
由XRD觀察發現,熱壓後的試片晶體結構在角度2θ=44.5º有優選方向產生。氧化物峰並未隨著溫度上昇有明顯的變化,唯有在380℃時,氧化物峰變弱。且晶粒尺寸在110nm~130nm之間熱電力比較佳,但對電阻率的影響不明顯。以硬度值方面來說,硬度值較高的試片可得較佳的熱電力與電阻率。以成分而言,分析中發現所有的熱壓試片皆含有很多的氧,且熱電力較佳的試片,其Te的含量較高且功率因子上也較好,而由縱深分析中得知,Bi2Te3材料結構內含大量的氧原子,約佔20-30%之間。

In this study, Bismuth Telluride compounds were fabricated by the metal-organo complex method plus subsequent hot-pressing. The effects of hot-pressing (HP) temperature and pressure on thermoelectric properties crystal structure, grain size, microstructure, defect and composition were investigated. Crystal structure, microstructure, defect and thermoelectric properties were characterized by X-ray diffraction (XRD), Field-Emission SEM (FE-SEM), micro-hardness, X-ray Photoelectron Spectroscopy (XPS) and thermoelectric measurement system, respectively.
The optimum Seebeck coefficient, -155 μVK-1, is attained at HP temperature 320℃ and HP pressure 260MPa, while the minimum resistivity, 2.7*10-3 ohm-cm, obtained at HP temperature 380℃ and HP pressure 260MPa. The maximum power factor is 6.1 W/m*K when the Seebeck coefficient is -130 μVK-1 and resistivity is 2.8*10-3 ohm-cm. The specimens after HP have a preferred orientation at 2θ=44.5o. The XRD results also show that the oxide peak does not change much with the rising temperature, except that at 380℃ the oxide peak becomes weaker with increasing HP pressure. The Hardness results also show that the better seebeck coefficient and lower resistivity were obtained in the high hardness value. The Seebeck coefficient was better in the grain size between 110 and 130 nm but the resistivity was not affected obviously. Large amount of oxygen (20-30%) are found in all HP specimen by the analysis of depth profiling. Furthermore, specimens having better Seebeck coefficient have higher Te content and larger power factor.
URI: http://hdl.handle.net/11455/9904
Appears in Collections:材料科學與工程學系

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