臺灣博碩士論文加值系統

PbTe 系合金是中溫區 (400~700 K) 熱電發電中最常用的熱電材料，其 ZT 值的研究主要集中在兩個方向：一、調控熱電塊材的載子濃度，進而增加塊材的電傳導率，以提升功率因子 (power factor) ；二、藉由摻雜使其散射聲子，降低熱傳導率而獲得較佳之熱電優值。
本研究以行星球磨法將鈉摻雜於 PbTe 粉體形成複合粉體，再以熱壓燒結於 450 ~ 550 ℃ 、 50 MPa 壓力下製成 PbTe : Na 複合塊材，檢討鈉摻雜量及熱壓燒結溫度對塊材的顯微結構及熱電性質的影響。
於製程上，有別於前人耗時耗能之熔煉法，本研究使用省時節能之行星球磨法，將鈉摻雜於PbTe粉體，再以熱壓燒結成為PbTe:Na熱電塊材。鈉摻雜量是由添加適量的Na2Te而得。利用行星球磨法所得之複合粉體之大小為1 ~ 5 μm，經熱壓燒結後會形成相對密度大於95%，晶粒大小為3 ~ 10 μm之緻密熱電塊材。摻雜的鈉粒子經熱壓燒結後並不存在於 PbTe 晶界上，而是於 PbTe 中產生間隙型固溶。
在熱電性質方面，PbTe : Na 塊材的電傳行為是隨鈉摻雜量而異，經鈉摻雜後會由p型半導體轉變成 n 型摻雜半導體的電傳行為。此外，功率因子 (S2σ) 則隨鈉添加量與量測溫度之增加而增加，其熱傳導率於整個量測溫度區間皆低於未摻雜之PbTe塊材，而鈉摻雜量 1.0 at.% 之 PbTe : Na 複合粉體以熱壓燒結於 500 ℃ 燒結所得之塊材，其熱電優值 (ZT) 於 700 K 時有最大值 0.81。
n 型傳導的 PbTe : Na塊材其室溫載子濃度、相對密度與導電率是隨熱壓燒結溫度之增加而增加；而Seebeck 係數是隨燒結溫度之增加而減少，其中鈉摻雜量為1.5 at.% 的PbTe：Na-550 ℃ 塊材，其功率因子在 650 K 時有最大值 1.33 mW/m-K2，此值為未摻雜鈉的 PbTe-550 ℃ 塊材之功率因子 (0.105 mW/m-K2) 的 28.4 倍。

To improve thermoelectric properties of PbTe:Na bulk materials, a manufacturing process that combined with planetary ball milling and hot-pressed sintering in the preparation of PbTe:Na bulk materials was studied. Samples with over 95% relative densities and 3~10 μm of grain sizes were obtained through hot-pressed at 500 ℃. Samples were measured and compared with those of raw ingots at temperatures from 300 K to 700 K to demonstrate the influence of Na contents on thermoelectric properties. The results revealed that increasing the Na contents improved the thermoelectric performance. PbTe: Na bulk showed the n-type conductivity. It was different from previous studies. A maximum ZT of 0.81 at 700 K was achieved for the n-type PbTe:1 at.% Na bulk.

目錄
中文摘要 i
Extended Abstract iii
誌謝 ix
目錄 xii
表目錄 xiv
圖目錄 xv
第一章 緒論 1
1-1 前言 1
1-2 研究目的 4
第二章 基礎理論與文獻回顧 6
2-1 基本熱電效應及其應用 6
2-1-1 Seebeck 效應 6
2-1-2 Peltier 效應 7
2-1-3 Thomson 效應 7
2-1-4熱電優質 (Figure of merit) 與能源轉換效率 8
2-2 熱電材料的介紹 10
2-2-1 熱電材料的種類 10
2-2-2 提高熱電材料性能的方法 12
2-3 熱電塊材的製備方法 14
2-3-1 熔煉法 14
2-3-2 粉末冶金法 15
2-3-3 熱壓燒結技術 16
2-4 碲化鉛物系之相關背景與研究動態 17
2-4-1 碲化鉛化合物簡介 17
2-4-2 相關研究之最新發展 17
第三章 實驗方法與步驟 37
3-1 實驗藥品及原料 37
3-2 實驗流程 37
3-3 碲化鉛：鈉複合粉體之製備 37
3-3-1 行星球磨製程 37
3-4 碲化鉛：鈉塊材之製備 38
3-4-1 生坯成形 38
3-4-2 熱壓燒結 (Hot-pressed Sintering ) 38
3-5 碲化鉛：鈉複合粉體及其塊材之材料特性分析 39
3-5-1 相鑑定分析 39
3-5-2 顯微結構觀察 39
3-5-3 塊材密度量測 39
3-6 碲化鉛：鈉塊材之熱電性質量測 40
3-6-1 電傳導率與 Seebeck 係數量測 40
3-6-2 載子濃度與遷移率量測 41
3-6-3 熱傳導率量測 42
第四章 結果與討論 50
4-1 PbTe:Na 複合粉體之特性 50
4-1-1 PbTe:Na 複合粉體的相鑑定分析 50
4-1-2 PbTe:Na 複合粉體的顯微結構 50
4-2 PbTe:Na 塊材之微觀結構及熱電性質 50
4-2-1相鑑定及晶格常數 50
4-2-2顯微結構 52
4-2-3 PbTe:Na 塊材的熱電性質 52
4-3 熱壓燒結溫度對 PbTe:Na 塊材之影響 59
4-3-1相鑑定及晶格常數 59
4-3-2顯微結構 61
4-3-3熱壓燒結溫度對 PbTe:Na 塊材的熱電性質之影響 61
第五章 結論 89
參考文獻 90

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