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Fabrication and Thermoelectric Behavior of Zn4Sb3 alloys
|Authors: ||Yi-Chen He|
|Contributors: ||NTOU:Institute of Materials Engineering|
mechanical alloying;Zn4Sb3;thermoelectric materials;ZT
|Issue Date: ||2011-06-30T07:24:36Z
|Abstract: ||本研究結合機械合金法(Mechanical Alloying, MA) 與真空燒結及真空熱壓成型技術製備具β相之Zn4Sb3合金，對合成之粉末及塊材均以XRD、DSC與SEM進行相關性質之分析，實驗結果顯示，設定組成為Zn4Sb3之Zn與Sb混合粉末經球磨後無法獲得單一β相之Zn4Sb3粉末，但添加過量0.6 at.% Zn之Zn4Sb3則可¬製備出近單一β相的Zn4Sb3¬粉末，利用此粉末真空燒結處理後，由於Zn於升溫期間易蒸發，造成燒結溫度673K時粉末中的Zn含量少於50 at. %，導致最後形成Sb及ZnSb平衡相。球磨過後之粉末進行真空熱壓成型，當提高熱壓溫度、熱壓溫度與持溫時間，皆可適度提昇塊材之相對密度，但熱壓溫度過高會造成Zn4Sb3相比例的減少。 由室溫至600K對熱壓塊材進行之熱電性質量測顯示，塊材呈現p型傳導特性，席貝克係數會隨著Zn4Sb3相之比例增加而增加，導電率則隨著Zn4Sb3相之比例增加而減少，Zn4Sb3塊材在600K時擁有最佳的熱電特性，其功率因子為1.31×10-3 Wm-1K-2，ZT值達0.81高於文獻與之分別利用真空熔煉和熱處理製備之單一β-Zn4Sb3，但略低於結合熔煉與熱壓法獲得者，熱壓製程顯然比燒製方式更適於製造具高ZT值之Zn4Sb3合金。|
In this research, thermoelectric Zn4Sb3 bulk specimens were produced by mechanical alloying of elemental powders and sintered by hot pressing. The phase transformations in the alloy system during mechanical alloying were systematically investigated using XRD, DSC and SEM. Single phase Zn4Sb3 was not obtained using a nominal stoichiometric composition, but near single phase Zn4Sb3 with remnant elemental Zn having a relatively high density was produced using a nominally 0.6 at. % Zn rich powders. Then followed by sintering process, the powders are exposed to high temperature processing, compositional changes occur due to compensate for Zn evaporation. Thus, to compensate for Zn evaporation, it might be produced by adding > 0.6 at. % excess Zn. The powders after ball-milling followed by hot pressing, when elevated the hot pressing temperature ,stress and holding time, it could increases the relative density appropriately. But the temperature of hot pressing is too high to increase the Zb4Sb3 phases. Thermoelectric and transport properties were evaluated for the hot pressed specimens at room temperature to 600K and compared with results of analogous studies. Experimental results that the Zn4Sb3 shows an intrinsic p-type behavior. The ratio of Zn4Sb3 phases increases with increasing Seebeck coefficient and decreasing electric conductivity.The maximum powder factor was found to be 1.31×10-3 Wm-1K-2 and ZT = 0.81 at 600K. And ZT=1.07 was calculated using the linear interpolation at 673K.
|Appears in Collections:||[材料工程研究所] 博碩士論文|
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