화학공학소재연구정보센터
Materials Science Forum, Vol.423-4, 377-379, 2003
Effect of FGMs on thermoelectric cooling properties of bismuth telluride
Every thermoelectric material shows high performance at a specific narrow temperature range. The temperature range with high performance can be expanded by joining the materials with different peak temperature. This is the concept of an FGM. The FGMs for Peltier cooling materials have never been reported though the FGMs for thermoelectric power generation were reported to enhance conversion efficiency. Bismuth telluride is the best material for cooling devices at around room temperature. Then we investigated the thermoelectric cooling properties for bismuth telluride with two steps graded structure FGM. Two kinds of melt-grown materials of p-type bismuth telluride (hereafter, sample 1 and sample 2) were used. The samples 1 and 2 of 3 mm square x 2.5 mm were joined to form an FGM of 3 mm square x 5 mm in length by soldering with ultrasonic vibration. Thermoelectric cooling properties were evaluated by observing the maximum temperature drop to electric current when the high temperature side was kept constant. When the high temperature side is kept at 370 K, the temperature drop of the monolithic sample 1 was 34.6 K, and 39.7 K for sample 2, because of the difference of the carrier density. In the case of the FGM, the temperature drop was 45.2 K when the sample 1 was placed at the high temperature side. On the other hand, the temperature drop was only 27.6 K when the sample 2 was placed at the high temperature side. From these results, it is clear that high performance can be obtained by forming an FGM when the proper material arrangement is performed along the temperature gradient.