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研究生：	周明達 Chou, Min-Da
論文名稱：	SrSi2 掺釔的熱電性質之研究 Effects of Y substitution on the thermoelectric performance of SrSi2
指導教授：	呂欽山 Lue, C.S.
學位類別：	碩士 Master
系所名稱：	理學院 - 物理學系 Department of Physics
論文出版年：	2009
畢業學年度：	97
語文別：	中文
論文頁數：	50
中文關鍵詞：	矽化物、熱電材料
外文關鍵詞：	Thermoelectrics, SrSi2
相關次數：	點閱：48 下載：1
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本篇論文是研究鹼土金屬鍶Sr 的矽化物SrSi2，藉由摻雜Y 和Sr 的比
例而形成Sr1-xYxSi2(x=0 0.03 0.05 0.08 0.1 0.15)。為了了解其熱電性質，我
們將這一系列的合金置於溫度10～300K 量測，測量合金的電阻率、熱導率
以及Seebeck coefficient。由實驗數據得知，絕大部分的熱導是由晶格熱導
率(κL)所提供的。並且發現晶格熱導率隨著Y/ Sr 比例的增加而減少。這是
因為Y 的取代而導致聲子和晶格間的無序散射效應增加。而電阻率在10～
300K 溫度範圍下，有類似半導體的電阻率隨溫度提高而下降的行為趨勢。
且在摻雜濃度x=0.08，電阻率有顯著的下降。在Seebeck coefficient 量測
上，發現溫度在80K 左右、摻雜濃度x=0.08 量得S=220μV/K 左右。
有了電阻率的顯著下降，以及Seebeck coefficient 的大幅提升，我們去
計算熱電優值 (figure of merit) ZT=S2T/κρ，可得到樣品Sr0.92Y0.08Si2 在室溫
300K 得ZT 值為0.4 左右。比起SrSi2 樣品本身(ZT=0.09 溫度417K)的熱
電優值大了一個數量級。
我們也對溫度範圍300K～800K 內由樣品Sr0.92Y0.08Si2 的電阻率ρ 及
Seebeck coefficient 作了模擬，在溫度380K 左右得到ZT 最大值為0. 417 左
右。

We report the results of the temperature-dependent electrical resistivity,
thermal conductivity, as well as Seebeck coefficient in Sr1-xYxSi2 with x ≤ 0.15.
The thermoelectric performance is improved and optimized with x=0.08. Ingots
were prepared with an arc-melting procedure and then annealed under 800℃ for
10 days.
Upon substituting Y onto the Sr sites, the electrical resistivity exhibit
semiconducting behavior and the room-temperature electrical resistivity
decreases with increasing the Y content for x ≤ 0.08. The thermal conductivity
also reduces with increasing the Y concentration. The Seebeck coefficient
exhibits a substantial increase and a maximum of about 220 μV/K at around 80
K has been found for x = 0.08
The figure of merit (ZT) is characterized by the Seebeck coefficient (S), the
thermal conductivity (κ) and the electrical resistivity (ρ) as ZT=S2T/κρ. These
promising effects lead to a significant enhancement in the thermoelectric
performance. A room-temperature ZT value of approximately 0.4 is achieved for
Sr0.92Y0.08Si2, about one order of magnitude larger than that of stoichiometric
SrSi2. Such a result has been associated with the effects of electron doping and
positive chemical pressure on the system.

1-前言....................................................................................................9
2-基礎理論..........................................................................................11
2-1 電傳導理論(電阻率 resistivity).............................................................12
2-2 熱傳導理論(熱導率 thermal conductivity)............................................15
2-3 倒逆過程( Umklapp process)..................................................................18
2-4 韋德曼-法蘭茲 定理(Wiedemann-Franz Law)......................................20
2-5 Seebeck coefficient……………………………………………………25
2-6 熱電優質 Figure of merit(ZT)................................................................27
3-製作過程與量測方法................................................................................29
3-1 樣品的製作過程.....................................................................................29
3-1-1 ARC 原理............................................................................29
3-1-2 樣品製備儀器...............................................................................30
3-2 物性參數的測量......................................................................................31
3-2-1 電阻率的測量................................................................................31
3-2-2 熱導率的測量................................................................................31
3-2-3 Seebeck coefficient 的測量..........................................................32
4-結果與數據討論分析................................................................................33
4-1 X-ray 的分析.............................................................................................33
4-2 Sr1-xYxSi2電阻率量測結果.......................................................................36
4-3 Sr1-xYxSi2熱導率與溫度的關係...............................................................38
4-4 Sr1-xYxSi2的Seebeck coefficient 對溫度的關係.....................................43
4-5 Sr1-xYxSi2的Figure of merit (ZT)..............................................................45
5-結論................................................................................................................48
參考文獻...........................................................................................................49
                                    

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校內：立即公開
校外：2009-07-02公開

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