燒結製程對含鎵之鉍銻碲熱電材料性質影響之研究

Effects of Sintering on Thermoelectric Properties of Gax(Bi0.5Sb1.5-xTe3).

郭玟伶(Wen-Ling Kuo)

指導教授 ： 陳貞光

國立臺北科技大學/工程學院/材料科學與工程研究所/碩士(2010年)

摘要

本研究以粉末冶金方式製備p型Gax(Bi0.5Sb1.5-xTe3) (x=0~0.4)四元化合物多晶塊材，將材料以真空熔煉、高能量球磨後，冷壓並進行300~500°C的真空燒結，探討Ga添加量及燒結溫度對微結構和熱電性質的影響。
當摻雜Ga取代Sb原子時，因原子間極性差異提高，減少錯置型缺陷的形成，使得Seebeck係數增加；在低溫燒結時，因Te的高蒸氣壓造成Te空位屬n型缺陷，亦會使Seebeck係數上升，而在高溫燒結時，Bi或Sb原子較易進入Te空位形成錯置型缺陷，則使Seebeck係數下降，因此在燒結溫度400-450°C間，可以觀察到Seebeck係數變化的轉折點。另一方面，導電率隨燒結溫度提高、緻密度上升而上升，但隨Ga濃度上升而下降；熱傳導率大致上隨燒結溫度提高而上升，隨Ga濃度上升而下降。
摻雜少量Ga原子取代Sb原子雖可提高Seebeck係數，並因Ga2Te3之析出使熱傳導率大幅降低，有助於提升熱電優值，但同時也降低了導電率，以致其提升效果受限；本研究顯示添加Ga之Ga0.1Bi0.5Sb1.4Te3材料以450°C真空燒結後，在室溫可獲得最高之熱電優值0.89。

關鍵字

熱電材料 ； 碲化鉍 ； Seebeck係數 ； 電阻率 ； 熱傳導 ； 粉末冶金

並列摘要

In this study, GaxBi0.5Sb1.5-xTe3 (x=0~0.4) materials are prepared via powder metallurgical routes. The compounds are vacuum induction melted, ball milled, and sintered under vacuum at different temperatures. The effects of Ga doping levels and sintering temperatures on the microstructure and thermoelectric properties are investigated.
The Seebeck coefficients increase with Ga additions, because Ga reduces numbers of antistructure defects due to the increased polarity between atoms. At lower sintering temperatures, Seebeck coefficients increase due to Te vacancy formation by its higher vapor pressure and forming n-type defects. At higher sintering temperatures, Seebeck coefficients decrease, since Bi or Sb tends to occupy Te sites and form substitutional antistructures. Therefore, Seebeck coefficients demonstrate a maximum at 400-450°C sintering temperatures. The electrical conductivity increases with sintering temperature but decreases with increasing Ga. The thermal conductivity also increases with sintering temperature but decreases with the amount of Ga.
Although the substitution of Ga for Sb can increase Seebeck coefficient, Ga2Te3 precipitations lead to simultaneous decrease of thermal conductivity and electrical conductivity, which inhibits ZT value from further improving. Results show that Ga0.1Bi0.5Sb1.4Te3 sintered at 450°C possesses the highest ZT value of 0.89.

並列關鍵字

thermoelectric materials ； Bi2Te3 ； Seebeck coefficient ； electrical resistivity ； thermal conductivity ； powder metallurgy

參考文獻

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