N型Bi1.5Sb0.5Te3-xSex與P型Bi0.5Sb1.5Te3-xSex熱電材料製作與物性研究

Abstract

碲化鉍 (Bi2Te3) 與其合金是可運用在200-500 K重要的熱電材料，而其熱電轉換效率或熱電優質係數可藉由參雜成分或參雜比例提升與優化。為了希望ZT能在高溫區有較最大轉換效率應用於廢熱回收，我們利用硒取代Bi0.5Sb1.5Te3-xSex系統中之碲來提升其在高溫區的熱電轉換效率係數。研究中，當硒參雜量增加時伴隨著電阻率、西貝克係數與熱傳導係數呈現有系統地改變，本研究結果發現在480K，x=0.5時有熱電優質係數0.79相較於無參雜的Bi0.5Sb1.5Te3提高了11%的熱電轉換效率。 藉由相同方法利用硒取代N型熱電材料Bi1.5Sb0.5Te3-xSex系統中之碲，並且發現熱傳導隨著硒的取代量增加而顯著的降低，因此我們成功的藉由熔煉與SPS燒結製作之樣品在500 K時將熱電優質係數由Bi1.5Sb0.5Te3 的0.13提高至Bi1.5Sb0.5TeSe2的0.55。

Bismuth telluride (Bi2Te3) and its alloys are the most well-known thermoelectric (TE) materials for heat-electricity conversion application in the temperature range 200-500 K. Their figure of merit ZT maximum can be tuned to higher or lower temperature by changing doping level or composition. With an attempt to tune ZT maximum to higher temperatures for waste heat recovery. We used selenium to substitute tellurium in Bi0.5Sb1.5Te3-xSex system. As selenium content increases, all the electrical, Seebeck coefficient, and thermal conductivity change systematically. ZT maximum of P-type Bi0.5Sb1.5Te3-xSex with x=0.5 is 0.79 at 480 K, the value is about 11% larger than that of pure Bi0.5Sb1.5Te3 at same temperature. Following this approach, the selenium substitution in N-type Bi1.5Sb0.5Te3 was also demonstrated. Thermal conductivity of Bi1.5Sb0.5Te3-xSex significantly decreases with the Se content increase. Consequently the ZT maximum increases from 0.13 of Bi1.5Sb0.5Te3 to 0.55 of Bi1.5Sb0.5TeSe2 at 500 K by combining melting and spark plasma sintering fabrications.