Mechanical Compatibility between Mg3(Sb,Bi)2 and MgAgSb in Thermoelectric Modules

Yifan Sun; Jiahui Fu; Yuji Ohishi; Keita Toh; Koichiro Suekuni; Kunihiro Kihou; Ushin Anazawa; Chul-Ho Lee; Ken Kurosaki

doi:10.1021/acsami.3c02544

Mechanical Compatibility between Mg₃(Sb,Bi)₂ and MgAgSb in Thermoelectric Modules

ACS Appl Mater Interfaces. 2023 May 17;15(19):23246-23254. doi: 10.1021/acsami.3c02544. Epub 2023 May 5.

Authors

Yifan Sun¹, Jiahui Fu², Yuji Ohishi², Keita Toh³, Koichiro Suekuni³, Kunihiro Kihou⁴, Ushin Anazawa⁴, Chul-Ho Lee⁴, Ken Kurosaki¹

Affiliations

¹ Institute for Integrated Radiation and Nuclear Science, Kyoto University, 2, Asashiro-Nishi, Kumatori, Sennan-gun 590-0494 Osaka, Japan.
² Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita 565-0871, Osaka, Japan.
³ Department of Applied Science for Electronics and Materials, Interdisciplinary Graduate School of Engineering Sciences, Kyushu University, Kasuga 816-8580, Fukuoka, Japan.
⁴ National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Umezono, Tsukuba 305-8568, Ibaraki, Japan.

PMID: 37144778
DOI: 10.1021/acsami.3c02544

Abstract

Thermoelectric (TE) modules are exposed to temperature gradients and repeated thermal cycles during their operation; therefore, mechanically robust n- and p-type legs are required to ensure their structural integrity. The difference in the coefficients of thermal expansion (CTEs) of the two legs of a TE module can cause stress buildup and the deterioration of performance with frequent thermal cycles. Recently, n-type Mg₃Sb₂ and p-type MgAgSb have become two promising components of low-temperature TE modules because of to their high TE performance, nontoxicity, and abundance. However, the CTEs of n-Mg₃Sb₂ and p-MgAgSb differ by approximately 10%. Furthermore, the oxidation resistances of these materials at increased temperatures are unclear. This work manipulates the thermal expansion of Mg₃Sb₂ by alloying it with Mg₃Bi₂. The addition of Bi to Mg₃Sb₂ reduces the coefficient of linear thermal expansion from 22.6 × 10^-6 to 21.2 × 10^-6 K^-1 for Mg₃Sb_1.5Bi_0.5, which is in excellent agreement with that of MgAgSb (21 × 10^-6 K^-1). Furthermore, thermogravimetric data indicate that both Mg₃Sb_1.5Bi_0.5 and MgAgSb are stable in air and Ar at temperatures below ∼570 K. The results suggest the compatibility and robustness of Mg₃Sb_1.5Bi_0.5 and MgAgSb as a pair of thermoelectric legs for low-temperature TE modules.

Keywords: Mg3Sb2; MgAgSb; mechanical properties; stability; thermal expansion; thermoelectric.