利用鑄造法製造三元合金之高效率散熱元件及其性質研究

Abstract

碲化鉍(Bi2Te3)合金為室溫下典型的熱電材料，若添加碲化銻(Sb2Te3) 合金或硒化鉍(Bi2Se3)於此材料中，將形成(Bi,Sb)2Te3 或Bi2(Te,Se)3 之三元 合金，其熱電優值(ZT)會產生明顯的增加而可應用的溫度範圍也將擴大。 第一年計劃將使用三種不同的氧化鋁模板來製造熱電材料之奈米線陣列， 此三種奈米模板的孔徑分別為20 奈米、80 奈米以及200 奈米，利用真空 鑄造方式，將Bi0.5Sb1.5Te3 金屬液壓入奈米孔洞中，待冷卻後即可得到 Bi0.5Sb1.5Te3 奈米線陣列。此奈米線陣列的晶體結構及材料的成分可利用X 光繞射分析，掃描式電子顯微鏡及電子探微儀等儀器分析，並在溫度300K 至600K 之間，進行量測Seebeck 係數、電阻係數和熱傳導係數隨溫度變化 的情形，並藉此計算出試片的ZT 值，求出Bi0.5Sb1.5Te3 奈米線陣列具有最 佳ZT 值時的孔徑大小及工作溫度範圍，並討論量子效應對其造成的影響。 另外也將利用穿透式電子顯微鏡探討在奈米線中三元合金的相分布、變化 情形，以及此變化對於奈米線熱電性質的影響。 在第二年的計畫中，將利用第一年實驗所得結果，再進一步去改變熱 電材料的成分，得到熱電特性最佳之P 型((Bi,Sb)2Te3)及N 型(Bi2(Te,Se)3) 熱電奈米線的成分，並製造此種P 型及N 型熱電奈米線陣列以P-N 對的方 式加以連接進行熱電元件的組裝，再加上金屬導電層及直流電源後，即可 量測其熱電性質及元件效能，期望能得到更高熱電轉換效率的熱電元件。

Bi2Te3 compound is a typical thermoelectric material under room temperature. Alloying this material with Sb2Te3 compound or Bi2Se3 compound will form the new ternary alloys (Bi,Sb)2Te3 and Bi2(Te,Se)3. The value of the figure of merit (ZT) for these materials will increase and the application temperature range of these materials will be extended. In the first year of this plan, we will use three different alumina nanotemplates with pore diameters of 20nm, 80nm and 200 nm respectively to fabricate the nanowire arrays. The Bi0.5Sb1.5Te3 nanowire arrays, the P type thermoelectric materials, will be produced by the pressure injection procedure. The crystallinity and composition of the Bi0.5Sb1.5Te3 nanowire arrays will be examined by X-ray diffraction analysis (XRD), scanning electron microscopy (SEM), and electron probe microanalysis (EPMA). The temperature dependence of the Seebeck coefficient, resistivity and thermal conductivity of the Bi0.5Sb1.5Te3 nanowire arrays will be measured at the temperature range between 300K and 600 K. Furthermore, the relationship between the phase distribution in the nanowires and theirs thermoelectric properties will also be discussed according to the TEM experiments. At the second year, the P type ((Bi,Sb)2Te3) nanowire arrays and N type (Bi2(Te,Se)3) nanowire arrays will be fabricated in the nanotemplates with a particular diameter according to the results of the previous experiment. By arranging P and N type pellets in a couple and forming a junction between them with a plated metal, it is possible to configure a series circuit which can keep all of the heat moving in the same direction. We will also measure the thermoelectric conversion effect of the thermoelectric nanowire-based device.