研究生: |
施經瑋 |
---|---|
論文名稱: |
多元合金之熱電性能研究 |
指導教授: | 廖建能 |
口試委員: | |
學位類別: |
碩士 Master |
系所名稱: |
工學院 - 材料科學工程學系 Materials Science and Engineering |
論文出版年: | 2004 |
畢業學年度: | 92 |
語文別: | 中文 |
論文頁數: | 64 |
中文關鍵詞: | 熱電 、多元 |
相關次數: | 點閱:3 下載:0 |
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通常一個好的熱電材料必須具備良好的電導係數及Seebeck係數,以及低熱導係數,這是一般傳統合金所無法具備的。相對於單一主元素之傳統合金,具多主元素之高熵合金係一嶄新的冶金概念。在目前已開發之部分高熵合金系統業已展現出極優異之機械性質與化學性質,然而高熵合金之電性質與熱電性質則尚未有詳盡之探討。本研究以half-heusler三元合金當作出發點,利用真空電弧熔煉製作合金,經由熱處理後,量測其熱電性質,找到兩個具有發展潛力的系統:ZrTiSnSiNi2、ZrTiSnGeNi2,室溫下熱電優值ZT分別為0.02與0.045。當在中高溫的範圍(250~300℃)時功率因子(S2/ρ)約可增加3~4倍,將成份改質為Zr0.9Ti0.9Nb0.2SnSiNi2,結果顯示室溫下的熱電優值ZT約為0.078。利用X光結晶繞射(XRD)、掃瞄式電子顯微鏡(SEM)與能量散佈光譜儀(EDS)鑑定出此二多元合金系統為具有半導體與金屬組成相的複合材料。
A good thermoelectric material requires high Seebeck coefficient (S) and electrical conductivity (σ) but low thermal conductivity (κ), which are not common found in traditional metallic alloys. As compound with traditional metallic alloy, high entropy alloy of multi constituent element is a newly developed metallurgical concept. A variety of different forms of the multi-element alloys have been demonstrated to possess superior mechanical and chemical properties. However, the electrical and thermoelectric properties of the multi-element alloys have not been thoroughly explored yet. In this study, multi-element alloys were prepared by arc-melting and thermal annealing. Their thermoelectric properties were characterized after appropriate sample preparation. We find two multi-element alloy systems based on half-Heusler structure:ZrTiSnSiNi2 and ZrTiSnGeNi2. The thermoelectric figure of merits (ZT , Z= S2/(ρ×κ)) of these multi-element alloys were equal to be 0.02 and 0.045, respectively, at room temperature. These multi-element alloys showed 3 times increase in power factor (S2/ρ) in the middle temperature range (250℃ to 300℃). By adding Nb element into the alloy forming Zr0.9Ti0.9Nb0.2SnSiNi2, the thermoelectric figure of merit was found to be 0.078 at room temperature. The multi- element alloys were identified to be a composite material containing semiconductor-like phase and metallic-like phase by X-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive spectrometer (EDS).
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