Phase Boundary Mapping to Obtain n-type Mg3Sb2-Based Thermoelectrics

Prashun Gorai, Eric Toberer, Saneyuki Ohno, Kazuki Imasato, Shashwat Anand, Hiromasa Tamaki, Stephen Kang, Hiroki Sato, Tsutomu Kanno, G. Snyder

Research output: Contribution to journalArticlepeer-review

270 Scopus Citations

Abstract

Zintl compounds make excellent thermoelectrics with many opportunities for chemically tuning their electronic and thermal transport properties. However, the majority of Zintl compounds are persistently p-type even though computation predicts superior properties when n-type. Surprisingly, n-type Mg3Sb2-based thermoelectrics have been recently found with exceptionally high figure of merit. Excess Mg is required to make the material n-type, prompting the suspicion that interstitial Mg is responsible. Here we explore the defect chemistry of Mg3Sb2 both theoretically and experimentally to explain why there are two distinct thermodynamic states for Mg3Sb2 (Mg-excess and Sb-excess) and why only one can become n-type. This work emphasizes the importance of exploring all of the multiple thermodynamic states in a nominally single-phase semiconductor. This understanding of the existence of multiple inherently distinct different thermodynamic states of the same nominal compound will vastly multiply the number of new complex semiconductors to be discovered for high zT thermoelectrics or other applications.
Original languageAmerican English
Pages (from-to)141-154
Number of pages14
JournalJoule
Volume2
Issue number1
DOIs
StatePublished - 2018

NREL Publication Number

  • NREL/JA-5K00-75995

Keywords

  • defects
  • semiconductors
  • thermodynamics
  • thermoelectrics

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