Development and Analysis of Improved Thermoelectric Materials
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Publisher:The Ohio State University
Series/Report no.:The Ohio State University. Department of Mechanical and Aerospace Engineering Honors Theses; 2018
Thermoelectric cooling devices, also called Peltier coolers, are devices based on the thermoelectric effect of materials and act in cooling mode. By adding an electrical potential on two sides of the material, a temperature gradient will be created. Thermoelectric cooling devices have many advantages, when compared to the commonly used compression-used refrigerators. For example, refrigerant-free, vibration free and compact. However, a vital disadvantage of thermoelectric cooling device is that it has a much lower device efficiency, comparing to compressor-based refrigerators. Thermoelectric coolers offer around 10-15% efficiency of ideal Carnot cycle, while compressor-based refrigerators provide 40-60% efficiency ideal Carnot cycle. The efficiency of thermoelectric cooler is influenced by the performance of thermoelectric used. Therefore, the purpose of this project was to improve the thermoelectric performance of Bi-Sb alloy. Bi-Sb alloys are of interest for thermoelectric cooling devices and it is believed that their heat pump efficiency can be enhanced by using CuBr resonant impurities. This project involves the synthesis of polycrystalline Bi-Sb alloys with different amounts of CuBr prepared via ingot casting. A concentrated master sample, with 0.5% CuBr, was developed first. Then, 2 times, 5 times and 10 times diluted samples was developed by diluting the master sample. After measurement, the master sample was found to have best thermoelectric performance, with a ZT of 0.27. The second step was to develop a single-crystalline sample via zone melting with the master sample mentioned above. The single-crystalline sample was found to have huge enhancement in thermoelectric performance, the ZT value of it was found to be 0.41. The results prove that CuBr dopant does enhanced the heat pump efficiency of Bi-Sb alloy. However, it is not as much as expected. Further effort can be done to improve the efficiency even more.
Academic Major: Mechanical Engineering