Mg Deficiency in Grain Boundaries of n-Type Mg3Sb2 Identified by Atom Probe Tomography

Jimmy Jiahong Kuo, Yuan Yu, Stephen Dongmin Kang, Oana Cojocaru-Mirédin, Matthias Wuttig, G. Jeffrey Snyder*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

26 Scopus citations

Abstract

Highly resistive grain boundaries significantly reduce the electrical conductivity that compromises the thermoelectric figure-of-merit zT in n-type polycrystalline Mg3Sb2. In this work, discovered is a Mg deficiency near grain boundaries using atom-probe tomography. Approximately 5 at% of Mg deficiency is observed uniformly in a 10 nm region along the grain boundary without any evidence of a stable secondary or impurity phase. The off-stoichiometry can prevent n-type dopants from providing electrons, lowering the local carrier concentration near the grain boundary and thus the local conductivity. This observation explains how nanometer scale compositional variations can dramatically determine thermoelectric zT, and provides concrete strategies to reduce grain-boundary resistance and increase zT in Mg3Sb2-based materials.

Original languageEnglish (US)
Article number1900429
JournalAdvanced Materials Interfaces
Volume6
Issue number13
DOIs
StatePublished - Jul 9 2019

Keywords

  • atom-probe tomography
  • grain boundary
  • thermoelectrics

ASJC Scopus subject areas

  • Mechanics of Materials
  • Mechanical Engineering

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