本研究針對Ru2-xFexNbAl (x= 0.00, 0.13, 0.25, 0.38, 0.50)系列樣品於10 K – 300 K溫度區間進行電阻率(ρ)、熱電勢(Ѕ)及熱導率(κ) 等熱電傳輸性質量測，並計算熱電優質(ZT)，以探討不同釕(Ru)和鐵(Fe)的摻雜比例對此系列樣品熱電傳輸影響。電阻率結果顯示隨鐵摻雜量增加整體數值降低，且行為由類似半導體性行為轉為類似金屬性行為，但由於此系列樣品殘餘電阻率比值很小，還是屬於半金屬。熱電勢量測結果為正值，顯示其主要傳輸載子為電洞，鐵摻雜量為 x = 0.13 時有最大值，其後隨著鐵摻雜量增加熱電勢降低。熱傳導率部分，隨著鐵比例的增加而下降，這是受點缺陷散射的影響，利用Wiedemann-Franz Law計算顯示此系列樣品主要由晶格熱導率貢獻。最後熱電優值在x=0.13最大值，比原型樣品提升了約兩倍，雖然熱導率和電阻率都有下降，但因熱電勢無法有效的提升，使得熱電優值除了x=0.13外，其他皆比原型樣品小。

In this thesis, the effects of partial Fe substitution on the Ru sites in the Ru2-xFexNbAl (x = 0.00, 0.13, 0.25, 0.38, 0.50) Heusler-type compounds were studied by means of electrical resistivity (ρ), Seebeck coefficient (S), and thermal conductivity (κ) measurement in the temperature range of 10 K to 300 K. The electrical resistivity of the Fe-substituted samples is found to decrease compared to that of the pristine Ru2NbAl sample. All studied samples could be classified as semimetal with a low residual resistivity ratio. The Seebeck coefficient of all studied samples is positive over the entire temperature range under investigation, suggesting that the dominant charge carriers are holes. We notice that the magnitude of the Seebeck coefficient increases for the x = 0.13 alloy, and decreases with further increase in the Fe content. The thermal conductivity decreases with increasing Fe content, presumably due to enhancement in the point-defect scattering. By using the Wiedemann-Franz Law, it is revealed that the thermal conductivity is mainly associated with phonons (lattice vibrations). An enhanced thermoelectric figure of merit (ZT) is achieved in Ru1.87Fe0.13NbAl (~6.7×10-3), about two times higher than that of Ru2NbAl (~3.5×10-3).

第一章 緒論 1
1.1 Fe2VAl簡介 1
1.2 Ru2VAl簡介 4
1.3 文獻回顧 4
1.4 研究動機 6
第二章 實驗原理 7
2.1電阻率 7
2.1.1電子的碰撞機制 10
2.2 Seebeck效應 13
2.2.1 Seebeck 係數 15
2.3 熱導率 19
2.3.1電子對熱導率的影響 21
2.3.2聲子對熱導率的影響 23
第三章 實驗方法 27
3.2量測系統與方法 27
3.2.1低溫冷卻系統 27
3.2.2電阻率量測方法 31
3.2.3熱導率量測方法 33
3.2.4 Seebeck係數量測方法 35
第四章 實驗結果與分析 37
4.1 X-Ray diffraction 分析 37
4.2 電阻率 (Electircal Resistivity) 39
4.3 熱電勢 (Seebeck coefficient) 43
4.4 熱傳導率 (Thermal conductivity) 47
4.5 熱電優值 (Figure of merit) 49
結論 51
參考文獻 53

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