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<p>N-type Mg<sub>3</sub>(Sb,Bi)<sub>2</sub> materials are promising for low-temperature thermoelectric applications, and their constituent elements are abundant and less expensive than tellurium. Mg<sub>3</sub>(Sb,Bi)<sub>2</sub>-based prototype modules have been recently reported by many groups, where the Mg<sub>3</sub>(Sb,Bi)<sub>2</sub> legs were mostly metallized by one-step monobloc sintering of Mg<sub>3</sub>(Sb,Bi)<sub>2</sub> and contact metal powders. However, monobloc sintering is unsuitable for industrial production. In this report, we present a new, simple method for the metallization of sintered n-type Mg<sub>3</sub>(Sb,Bi)<sub>2</sub>, which involves solid-state direct bonding (SSDB) of Mg/Cu double metal foils at an elevated temperature. Using foils, the formation of contacts with flat interfaces and constant thicknesses is easily achievable. Mg was chosen for contact to prevent Mg deficiency in the interfacial Mg<sub>3</sub>(Sb,Bi)<sub>2</sub> region, and a Cu layer was wrapped around the Mg for conventional soldering. SSDB at an optimum temperature of 723&#xa0;K produces structurally perfect ohmic contacts with a low resistivity of approximately 53.8 μΩ cm<sup>2</sup> in the pristine sample, and the thermoelectric properties of Mg<sub>3</sub>(Sb,Bi)<sub>2</sub> are not deteriorated by this process. Temperature is a critical parameter for successful SSDB, and foil delamination or the loss of liquefied Mg occurs outside a narrow temperature window. The stability of Mg contacts was tested at 473&#xa0;K in an ambient air-filled oven for up to 7&#xa0;days, and oxidation-induced problems were not detected; rather, the contact resistivity decreased after aging test. Using SSDB, a product-sized thermoelectric generator (50&#xa0;mm × 50&#xa0;mm footprint) containing 127 pairs of Mg<sub>3</sub>(Sb,Bi)<sub>2</sub>–(Bi,Sb)<sub>2</sub>Te<sub>3</sub> legs was successfully fabricated. The maximum power of this module is approximately 3.8 W when a temperature gradient of 150&#xa0;K is applied. As a result, the applicability of SSDB using Mg/Cu foils was demonstrated at the module level, and we speculate that it is compatible with mass fabrication.</p>

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A large-area thermoelectric generator fabricated by direct bonding of Mg/Cu double metal foils on sintered Mg3(Sb,Bi)2

  • 期刊论文

  • 发表日期：

    2025年8月11日

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  • Sung-Jae Joo,
  • Ji-Hee Son,
  • Jeongin Jang,
  • JongHo Park,
  • Bong-Seo Kim

摘要

N-type Mg3(Sb,Bi)2 materials are promising for low-temperature thermoelectric applications, and their constituent elements are abundant and less expensive than tellurium. Mg3(Sb,Bi)2-based prototype modules have been recently reported by many groups, where the Mg3(Sb,Bi)2 legs were mostly metallized by one-step monobloc sintering of Mg3(Sb,Bi)2 and contact metal powders. However, monobloc sintering is unsuitable for industrial production. In this report, we present a new, simple method for the metallization of sintered n-type Mg3(Sb,Bi)2, which involves solid-state direct bonding (SSDB) of Mg/Cu double metal foils at an elevated temperature. Using foils, the formation of contacts with flat interfaces and constant thicknesses is easily achievable. Mg was chosen for contact to prevent Mg deficiency in the interfacial Mg3(Sb,Bi)2 region, and a Cu layer was wrapped around the Mg for conventional soldering. SSDB at an optimum temperature of 723 K produces structurally perfect ohmic contacts with a low resistivity of approximately 53.8 μΩ cm2 in the pristine sample, and the thermoelectric properties of Mg3(Sb,Bi)2 are not deteriorated by this process. Temperature is a critical parameter for successful SSDB, and foil delamination or the loss of liquefied Mg occurs outside a narrow temperature window. The stability of Mg contacts was tested at 473 K in an ambient air-filled oven for up to 7 days, and oxidation-induced problems were not detected; rather, the contact resistivity decreased after aging test. Using SSDB, a product-sized thermoelectric generator (50 mm × 50 mm footprint) containing 127 pairs of Mg3(Sb,Bi)2–(Bi,Sb)2Te3 legs was successfully fabricated. The maximum power of this module is approximately 3.8 W when a temperature gradient of 150 K is applied. As a result, the applicability of SSDB using Mg/Cu foils was demonstrated at the module level, and we speculate that it is compatible with mass fabrication.