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Published July 9, 2019 | Supplemental Material
Journal Article Open

Mg Deficiency in Grain Boundaries of n-Type Mg_3Sb_2 Identified by Atom Probe Tomography

Abstract

Highly resistive grain boundaries significantly reduce the electrical conductivity that compromises the thermoelectric figure‐of‐merit zT in n‐type polycrystalline Mg_3Sb_2. 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 Mg_3Sb_2‐based materials.

Additional Information

© 2019 Wiley-‐VCH Verlag GmbH & Co. KGaA, Weinheim. Version of Record online: 15 May 2019; Manuscript revised: 08 March 2019; Manuscript received: 19 April 2019. Funding Information: DPG. Grant Number: SFB 917; NSF DMREF. Grant Numbers: 1334713, 1334351, 1333335, DMR‐0420532; ONR‐DURIP. Grant Numbers: N00014‐0400798, N00014‐0610539, N00014‐0910781, N00014‐1712870; MRSEC. Grant Number: NSF DMR‐1720139; Soft and Hybrid Nanotechnology Experimental. Grant Number: NSF ECCS‐1542205.

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Created:
August 22, 2023
Modified:
October 20, 2023