| Summary: | 碩士 === 國立臺灣師範大學 === 物理學系 === 101 === 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.
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