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Vol.59, No.12, 904 ~ 911, 2021
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| Title |
| Synthesis of Nb0.8Hf0.2FeSb0.98Sn0.02 and Hf0.25Zr0.25Ti0.5NiSn0.98Sb0.02 Half-Heusler Materials and Fabrication of Thermoelectric Generators |
| Sung-jae Joo , Ji-hee Son , Jeongin Jang , Bong-seo Kim , Bok-ki Min |
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| Abstract |
| In this study, half-Heusler (HH) thermoelectric materials Nb0.8Hf0.2FeSb0.98Sn0.02 (p-type) and Hf0.25Zr0.25Ti0.5NiSn0.98Sb0.02 (n-type) were synthesized using induction melting and spark plasma sintering. For alloying, a conventional induction melting technique was employed rather than arc melting, for mass production compatibility, and the thermoelectric properties of the materials were analyzed. The maximum dimensionless figures of merit (zTmax) were 0.75 and 0.82 for the p- and n-type material at 650 ℃ and 600 ℃, respectively. These materials were then used to fabricate generator modules, wherein two pairs of p- and nlegs without interfacial metal layers were brazed on direct bonded copper (DBC)/Al2O3 substrates using a Zrbased alloy. A maximum power of 0.57 W was obtained from the module by applying a temperature gradient of 476 ℃, which corresponds to a maximum power density of 1.58W cm -2 when normalized by the area of the material. The maximum electrical conversion efficiency of the module was 3.22% at 476 ℃ temperature gradient. This value was negatively affected by the non-negligible contact resistivity of the brazed interfaces, which ranged from 6.63 × 10 -9 Ω ㎡ to 7.54 × 10 -9 Ω ㎡ at hot-side temperatures of 190 ℃ and 517 ℃, respectively. The low electrical resistivity of the HH materials makes it especially important to develop a brazing technique for ultralow resistance contacts.
(Received August 11 2021; Accepted August 31, 2021) |
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| Key Words |
| thermoelectric, half-Heusler, module, brazing, contact resistivity |
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