New insight into the material parameter B to understand the enhanced thermoelectric performance of Mg[subscript 2]S[subscript n1−x−y]Ge[subscript x]Sb[subscript y]
Author(s)Liu, Weishu; Zhou, Jiawei; Jie, Qing; Li, Yang; Kim, Hee Seok; Bao, Jiming; Chen, Gang; Ren, Zhifeng; ... Show more Show less
New insight into the material parameter B to understand the enhanced thermoelectric performance of Mg2Sn1−x−yGexSby
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Historically, a material parameter B incorporating weighted mobility and lattice thermal conductivity has guided the exploration of novel thermoelectric materials. However, the conventional definition of B neglects the bipolar effect which can dramatically change the thermoelectric energy conversion efficiency at high temperatures. In this paper, a generalized material parameter B* is derived, which connects weighted mobility, lattice thermal conductivity, and the band gap. Based on the new parameter B*, we explain the successful tuning of the electron and phonon transport in Mg[subscript 2]S[subscript n1−x−y]Ge[subscript x]Sb[subscript y], with an improved ZT value from 0.6 in Mg[subscript 2]Sn[subscript 0.99]Sb[subscript 0.01] to 1.4 in Mg[subscript 2]Sn[subscript 0.73]Ge[subscript 0.25]Sb[subscript 0.02]. We uncover that the Ge alloying approach simultaneously improves all the key variables in the material parameter B*, with an ∼25% enhancement in the weighted mobility, ∼27% band gap widening, and ∼50% reduction in the lattice thermal conductivity. We show that a higher generalized parameter B* leads to a higher optimized ZT in Mg[subscript 2]Sn[subscript 0.73]Ge[subscript 0.25]Sb[subscript 0.02], and some common thermoelectric materials. The new parameter B* provides a better characterization of material's thermoelectric transport, particularly at high temperatures, and therefore can facilitate the search for good thermoelectric materials.
DepartmentMassachusetts Institute of Technology. Department of Mechanical Engineering
Energy and Environmental Science
Royal Society of Chemistry
Liu, Weishu et al. “New Insight into the Material Parameter B to Understand the Enhanced Thermoelectric Performance of Mg[subscript 2]S[subscript n 1−x−y]Ge[subscript X]Sb]subscript Y].” Energy Environ. Sci. 9.2 (2016): 530–539.
Author's final manuscript