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Mg Deficiency in Grain Boundaries of n‐Type Mg 3 Sb 2 Identified by Atom Probe Tomography
Author(s) -
Kuo Jimmy Jiahong,
Yu Yuan,
Kang Stephen Dongmin,
CojocaruMirédin Oana,
Wuttig Matthias,
Snyder G. Jeffrey
Publication year - 2019
Publication title -
advanced materials interfaces
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.671
H-Index - 65
ISSN - 2196-7350
DOI - 10.1002/admi.201900429
Subject(s) - grain boundary , materials science , atom probe , impurity , crystallite , thermoelectric effect , condensed matter physics , conductivity , dopant , electrical resistivity and conductivity , thermoelectric materials , atom (system on chip) , analytical chemistry (journal) , doping , metallurgy , thermal conductivity , microstructure , composite material , optoelectronics , thermodynamics , chemistry , electrical engineering , physics , organic chemistry , chromatography , computer science , embedded system , engineering
Highly resistive grain boundaries significantly reduce the electrical conductivity that compromises the thermoelectric figure‐of‐merit zT in n‐type polycrystalline Mg 3 Sb 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 3 Sb 2 ‐based materials.