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Vol.62, No.10, 796 ~ 803, 2024
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| Title |
| Analysis of Thermoelectric Properties of Hot-deformed Bismuth Telluride Sintered Materials |
| 주성재 Sung-jae Joo , 손지희 Ji-hee Son , 장정인 Jeongin Jang , 민복기 Bok-ki Min , 김봉서 Bong-seo Kim , 홍종간 Jonggan Hong , 이대근 Dae-keun Lee , 김형모 Hyungmo Kim |
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| Abstract |
| Bismuth telluride (Bi2Te3)-based alloys are widely used for thermoelectric cooling and power generation at low temperatures, and they are the only commercially available materials for thermoelectric applications below 500 K. The rhombohedral unit cell with a large c/a lattice constant ratio consisting of - Te-Bi-Te-Bi-Te- stacked layers inevitably brings about a large anisotropy in transport properties, which is why texturing is very important in polycrystalline Bi2Te3 alloys for maximum performance. In this report, p and n-type polycrystalline Bi2Te3 alloys were synthesized and hot-deformed to investigate the effects of texturing on thermoelectric properties. Hot deformation (HD) induces the strong alignment of (00l) orientations along the compression direction, and a remarkable increase in the orientation factor F of (00l) orientations is observed after HD in both p and n-type materials. All of the hot-deformed polycrystalline samples showed increased electrical conductivity (σ), power factor (PF), and thermal conductivity (κ) in the in-plane (IP) direction, and vice versa in the out-of-plane (OOP) direction, which makes the IP direction of the hot-deformed bodies more favorable for module fabrication in terms of power factor, for both p and n-type Bi2Te3-based alloys. However, due to the different degree of anisotropy of κ and σ, the figures of merit (zT) were maximized in the OOP direction in the p-type materials after HD, whereas the zTs of the n-type materials were higher in the IP direction. This occurs because the anisotropy factor of electron conduction is higher than that of hole conduction, which more than offsets the advantage of the smaller κ in the c-direction of n-type Bi2Te3. The maximum zT of 1.33 (OOP) and 0.90 (IP) were obtained after HD from the p and n-type Bi2Te3 alloys, respectively, which were 9.3% and 18.4% higher than those of as-sintered materials. |
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| Key Words |
| thermoelectric, bismuth telluride, hot deformation, texturing, anisotropy |
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