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Issue 13, 2020
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Charge compensation weakening ionized impurity scattering and assessing the minority carrier contribution to the Seebeck coefficient in Pb-doped Mg3Sb2 compounds

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Abstract

This work reports the electrical and thermal transport processes in p-type Pb-doped Mg3(1+x)Sb2−yPby (0.02 ≤ x ≤ 0.08; 0 ≤ y ≤ 0.02) compounds. Low-energy electron acceptor defects Mg vacancies Image ID:d0cp00266f-t1.gif are easy to form, which can provide holes and make p-type transport in the Mg3Sb2 matrix. However, with an increase in excess Mg, the transport behavior changes from p type to n type as manifested synergistically by both the Hall coefficient and Seebeck coefficient. This indicates the effective role of Mg in tuning carrier type and concentration for a pristine Mg3Sb2 compound. Upon substitution of Sb by Pb, the hole concentration slightly increases, and mobility is greatly improved by 133% at room temperature. The significant increase in mobility is attributed to the weakening ionized impurity scattering, stemming from the decreasing Image ID:d0cp00266f-t2.gif concentration induced by Pb doping. Thus, the power factor is enhanced with a 146% improvement at room temperature. Consequently, the figure of merit ZT of the Pb-doped sample is 1.8 times larger than the pristine one at around 300 K. Moreover, the non-degenerate transport behavior revealed by electrical properties is simply analyzed regarding the effects of minority carriers on the overall Seebeck coefficient. This study proposes a new strategy of charge compensation for improving mobility and a simple way to guide the prediction about the onset of bipolar conduction for Mg3Sb2-based compounds and other potential thermoelectric materials.

Graphical abstract: Charge compensation weakening ionized impurity scattering and assessing the minority carrier contribution to the Seebeck coefficient in Pb-doped Mg3Sb2 compounds

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Article information


Submitted
16 Jan 2020
Accepted
11 Mar 2020
First published
11 Mar 2020

Phys. Chem. Chem. Phys., 2020,22, 7012-7020
Article type
Paper

Charge compensation weakening ionized impurity scattering and assessing the minority carrier contribution to the Seebeck coefficient in Pb-doped Mg3Sb2 compounds

Q. Zhang, J. Hou, J. Fan, S. Chen, W. Fan, H. Zhang, W. Wang, Y. Wu and B. Xu, Phys. Chem. Chem. Phys., 2020, 22, 7012
DOI: 10.1039/D0CP00266F

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