Inhibiting Mg Diffusion and Evaporation by Forming Mg‐Rich Reservoir at Grain Boundaries Improves the Thermal Stability of N‐Type Mg3Sb2 Thermoelectrics

Author:

Geng Yang1,Li Zerong1,Lin Zehao1,Liu Yali1,Lai Qiangwen1,Wu Xuelian1,Hu Lipeng1,Liu Fusheng1,Yu Yuan2,Zhang Chaohua1ORCID

Affiliation:

1. College of Materials Science and Engineering Shenzhen Key Laboratory of Special Functional Materials Shenzhen Engineering Laboratory for Advanced Technology of Ceramics Guangdong Research Center for Interfacial Engineering of Functional Materials Institute of Deep Underground Sciences and Green Energy Shenzhen University Shenzhen 518060 P. R. China

2. Institute of Physics (IA) RWTH Aachen University 52056 Aachen Germany

Abstract

AbstractN‐type Mg3Sb2‐based thermoelectric materials show great promise in power generation due to their mechanical robustness, low cost of Mg, and high figure of merit (ZT) over a wide range of temperatures. However, their poor thermal stability hinders their practical applications. Here, MgB2 is introduced to improve the thermal stability of n‐type Mg3Sb2. Enabled by MgB2 decomposition, extra Mg can be released into the matrix for Mg compensation thermodynamically, and secondary phases of Mg─B compounds can kinetically prevent Mg diffusion along grain boundaries. These synergetic effects inhibit the formation of Mg vacancies at elevated temperatures, thereby enhancing the thermal stability of n‐type Mg3Sb2. Consequently, the Mg3.05(Sb0.75Bi0.25)1.99Te0.01(MgB2)0.03 sample exhibits negligible variation in thermoelectric performance during the 120‐hour continuous measurement at 673 K. Moreover, the ZT of n‐type Mg3Sb2 can be maintained by adding MgB2, reaching a high average ZT of ≈1.1 within 300–723 K. An eight‐pair Mg3Sb2‐GeTe‐based thermoelectric device is also fabricated, achieving an energy conversion efficiency of ≈5.7% at a temperature difference of 438 K with good thermal stability. This work paves a new way to enhance the long‐term thermal stability of n‐type Mg3Sb2‐based alloys and other thermoelectrics for practical applications.

Funder

Science, Technology and Innovation Commission of Shenzhen Municipality

National Basic Research Program of China

Publisher

Wiley

Subject

Biomaterials,Biotechnology,General Materials Science,General Chemistry

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