| 摘要: | 碲化鉛(Lead Telluride, PbTe)為常見的中溫型熱電材料，具有優良的化學穩定性、高載子濃度與低熱傳導係數等優點，經不同摻雜物的添加可使其顯現n型或p型的傳輸性質，而摻雜Ag、Sb後形成之四元合金，稱為LAST (Lead, Antimony, Silver, Tellurium)合金，高ZT值為其最大特點。 本研究利用真空熔煉法結合熱壓燒結(450℃,1hr)製備AgPb18+xSbTe20 (x=0, 2, 4)，分別對其成分、微結構與熱電性質(載子特性、導電度及Seebeck係數)進行分析，探討Pb含量以及熱處理對LAST合金性質之影響。研究發現在量測溫度範圍內(室溫至427 ℃)，所有合金均呈現n型半導體之傳輸行為。另外，提高Pb含量可增加載子濃度，使導電度提升，但遷移率並未隨Pb含量持續增加，而經熱處理之合金遷移率可獲得改善，且整體溫度範圍內之功率因子(Power factor)皆有所提升。本研究所得最佳功率因子出現在熔煉後經熱處理再施以熱壓燒結之AgPb20SbTe20 與AgPb22SbTe20，於427℃時皆可達約1.7×10-3 W/m•K2 。 PbTe is a moderate-temperature thermoelectric, co-doping of Ag and Sb in PbTe (Lead, Antimony, Silver and Tellurium, LAST) has caused great interest in recent years due to its high ZT value. AgPb18+xSbTe20 (x=0, 2, 4) were fabricated by the combination process of melting and hot pressing methods. The influences of Pb content and heat treatment on the thermoelectric performance, including electrical conductivity and Seebeck coefficient, were investigated in this work. For all of samples, the electrical conductivity and the Seebeck coefficient exhibited the typical n-type semiconductor behavior in the temperature ranges from room temperature to 427 ℃. Higher Pb content increases electrical conductivity, but mobility decreases at highest Pb content (x=4). Furthermore, after heat treatment for as-cast alloys at 800 ℃ for 10 hours, the sintered sample show better mobility, which resulted in higher power factor in all temperatures compared to non heat treatment ones. According to the results, for AgPb20SbTe20 and AgPb22SbTe20 which were hot pressed after heat treatment, has maximum power factor about 1.7×10-3 W/m•K2 at 427 ℃. |
