臺灣博碩士論文加值系統

本實驗選擇一熱電材料Bi2Te3為基材，在其中混和另一半導體材料As2S3，其熔點較Bi2Te3為低而能隙較Bi2Te3為高。利用材料熔點之差異，採用粉末冶金技術，製備複合材料(As2S3¬)x/ (Bi2Te3)1-x ,其中 x=0、0.05、0.1、0.2，在溫度為As2S3熔點之上但在Bi2Te3熔點之下，將As2S3與Bi2Te3粉末熱壓成型。藉由液相As2S3在固相Bi2Te3基材中之擴散，以期產生近乎奈米及之微結構。
藉由X-ray繞射分析(XRD)、場發射式電子顯微鏡(FE-SEM)搭配X光能量分散光譜儀(EDS)，以分析成分及觀察微結構；並在50K至300K之間進行電阻率、Seebeck係數及熱傳導係數隨溫度變化的量測。
電阻率量測結果顯示，多數樣品呈現金屬性傳導，電阻率隨溫度上升而上升。Seebeck係數顯現出所有樣品皆為n-type傳導，皆隨著溫度上升而增加。熱傳導值與添加量關係不明顯，所有樣品ZT值隨著溫度上升而增加。ZT值在x=0，300K時有最大值為0.22。

In this study, Bi2Te3 was selected as a matrix material and a semiconductor material As2S3 with higher energy gap was incorporated to from microstructures in it. For this purpose, the composites (As2S3¬)x/ (Bi2Te3)1-x ,with x=0,0.05,0.1,0.25 were prepared by power metallurgy. The melting point of As2S3 is lower then that of Bi2Te3. As Bi2Te3 and As2S3 powders were mixed homogeneously and hot-pressed at a temperature slightly above the melting point of As2S3 liquidized As2S3 may diffuse between Bi2Te3 solid and then from the nano-scale microstructure in the matrices.
The composition and microstructure of these two-component composites were examined by X-ray and SEM. Thermoelectric properties including Seebeck coefficient, electric resistivity, and thermal conductivity were measured from 50 K to 300K.
The resistivity of composites were increased with increasing temperature. The Seebeck coefficient was negative in the temperature range studied. The study suggests that the electron-type carriers dominate the thermoelectric transport. The thermal conductivity increases as small amount of As2S3 added. The maximum figure of merit (ZT) of (As2S3)0/(Bi2Te3)1 is 0.22 at 300K.

摘要 I
Abstract II
目錄 II
圖目錄 V
表目錄 VII
第一章 前言 1
1-1 前言 1
1-1-2 研究背景 2
1-1-3 文獻回顧 6
1-1-4 熱電材料的分類與應用 10
1-2研究動機與方向 12
第二章 基本特性與基礎理論 15
2-1 基本特性 15
2-1-1 Bi2Te3基本特性 15
2-1-2 As2S3基本特性 17
2-2基礎理論 19
2-2-1 Seebeck效應 19
2-2-2 Peltier效應 21
2-2-3 Thomson效應 22
2-3 熱電材料物理性質 24
2-3-1 電阻率 24
2-3-2 Seebeck係數 27
2-3-3 熱傳導率 30
2-3-4 霍爾效應 39
第三章 實驗方法與步驟 43
3-1 實驗流程 43
3-2 試片製備 44
3-2-1 石英管處理 44
3-2-2 材料裝填及封管 45
3-2-3高溫搖擺爐熔融及淬火 47
3-2-4以粉末冶金之冷壓與熱壓法製作樣品 49
3-3 結構與成份分析 50
3-3-1 粉末X光繞射（XRD） 50
3-3-2 場發射型掃描式電子顯微鏡 （FE-SEM） 51
3-4 熱電特性量測 52
3-4-1 室溫霍爾量測 52
3-4-2 熱電量測系統 53
3-4-3 實驗控制程式 54
3-4-4 電阻率量測 59
3-4-5 熱傳導率量測 60
3-4-6 Seebeck係數量測 62
第四章 實驗結果與討論 63
4-1 試片外觀、微結構與成份分析 63
4-1-1 (As2S3)X/(Bi2Te3)1-X複合物之物性與外觀 63
4-1-2 粉末X光繞射分析（XRD） 64
4-1-3金相顯微鏡分析（OM） 67
4-1-4場發射型掃描式電子顯微鏡分析（FE-SEM） 70
4-2 熱電特性分析 77
4-2-1 室溫霍爾量測分析 77
4-2-2 電阻率量測 77
4-2-3 Seebeck係數 80
4-2-4 熱傳導率 83
4-2-5 優值（figure of merit）ZT值 89
第五章 結論 91
第六章 參考文獻 95

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