Understanding the Intrinsic P-Type Behavior and Phase Stability of Thermoelectric α-Mg3Sb2

Xiaoyu Chong, Pin Wen Guan, Yi Wang, Shun Li Shang, Jorge Paz Soldan Palma, Fivos Drymiotis, Vilupanur A. Ravi, Kurt E. Star, Jean Pierre Fleurial, Zi Kui Liu

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9 Scopus citations

Abstract

α-Mg3Sb2 is an excellent thermoelectric material through excess-Mg addition and n-type impurity doping to overcome its persistent p-type behavior. It is generally believed that the role of excess-Mg is to compensate the single Mg vacancy to realize n-type carrier conduction. In contrary to this belief, the present work indicates that the role of excess-Mg is to compensate the electronic charge of defect complex (VMg(2) + MgI)1-. The Mg solubility in α-Mg3+xSb2 is quite small when only considering a single defect, but it enlarged up to x = 0.011 with the defect complex (VMg(2) + MgI)1-, which is more reasonable as supported by experiments. Under Mg-poor conditions, VMg(1)2- and VMg(2)2- are the dominant defects, and their concentrations can reach (1.05-1.18) × 1019 cm-3 at 1200 K. Under Mg-rich conditions, (VMg(2) + MgI)1- is found to be the dominant reason for strong p-type behavior, and their concentrations can reach as high as 3.5 × 1020 cm-3, which shifts the Fermi level closer to the valence band maximum. The predicted carrier concentrations in the range 1017-1020 cm-3 are in the same range found experimentally for pure p-type α-Mg3Sb2.

Original languageEnglish (US)
Pages (from-to)6600-6608
Number of pages9
JournalACS Applied Energy Materials
Volume1
Issue number11
DOIs
StatePublished - Nov 26 2018

All Science Journal Classification (ASJC) codes

  • Chemical Engineering (miscellaneous)
  • Energy Engineering and Power Technology
  • Electrochemistry
  • Materials Chemistry
  • Electrical and Electronic Engineering

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    Chong, X., Guan, P. W., Wang, Y., Shang, S. L., Paz Soldan Palma, J., Drymiotis, F., Ravi, V. A., Star, K. E., Fleurial, J. P., & Liu, Z. K. (2018). Understanding the Intrinsic P-Type Behavior and Phase Stability of Thermoelectric α-Mg3Sb2. ACS Applied Energy Materials, 1(11), 6600-6608. https://doi.org/10.1021/acsaem.8b01520