TY - JOUR
T1 - Nb-Mediated Grain Growth and Grain-Boundary Engineering in Mg3Sb2-Based Thermoelectric Materials
AU - Luo, Ting
AU - Kuo, Jimmy J.
AU - Griffith, Kent J.
AU - Imasato, Kazuki
AU - Cojocaru-Mirédin, Oana
AU - Wuttig, Matthias
AU - Gault, Baptiste
AU - Yu, Yuan
AU - Snyder, G. Jeffrey
N1 - Funding Information:
T.L. and J.J.K. contributed equally to this work. TL acknowledges the financial support from the Alexander von Humboldt Foundation. YY, OCM, MW acknowledge the financial support of DFG (German Science Foundation) within the project SFB 917 nanoswitches. G.J.S., K.I., K.J.G., and J.J.K. acknowledge the support of award 70NANB19H005 from U.S. Department of Commerce, National Institute of Standards and Technology as part of the Center for Hierarchical Materials Design (CHiMaD). This work made use of the IMSERC X‐ray and NMR facilities at Northwestern University, which have received support from the Soft and Hybrid Nanotechnology Experimental (SHyNE) Resource (NSF ECCS‐2025633), Int. Institute of Nanotechnology, and Northwestern University. This research used resources of the Advanced Photon Source, a U.S. Department of Energy (DOE) Office of Science User Facility, operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE‐AC02‐06CH11357. The authors thank Dr. Mahalingam Balasubramanian for assistance with XAS measurements at beamline 20‐BM at the Advanced Photon Source, Argonne National Laboratory.
Funding Information:
T.L. and J.J.K. contributed equally to this work. TL acknowledges the financial support from the Alexander von Humboldt Foundation. YY, OCM, MW acknowledge the financial support of DFG (German Science Foundation) within the project SFB 917 nanoswitches. G.J.S., K.I., K.J.G., and J.J.K. acknowledge the support of award 70NANB19H005 from U.S. Department of Commerce, National Institute of Standards and Technology as part of the Center for Hierarchical Materials Design (CHiMaD). This work made use of the IMSERC X-ray and NMR facilities at Northwestern University, which have received support from the Soft and Hybrid Nanotechnology Experimental (SHyNE) Resource (NSF ECCS-2025633), Int. Institute of Nanotechnology, and Northwestern University. This research used resources of the Advanced Photon Source, a U.S. Department of Energy (DOE) Office of Science User Facility, operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357. The authors thank Dr. Mahalingam Balasubramanian for assistance with XAS measurements at beamline 20-BM at the Advanced Photon Source, Argonne National Laboratory. Open access funding enabled and organized by Projekt DEAL.
Publisher Copyright:
© 2021 The Authors. Advanced Functional Materials published by Wiley-VCH GmbH.
PY - 2021/7/9
Y1 - 2021/7/9
N2 - The poor carrier mobility of polycrystalline Mg3Sb2 at low temperatures strongly degrades the thermoelectric performance. Ionized impurities are initially thought to dominate charge carrier scattering at low temperatures. Accordingly, the increased electrical conductivity by replacing Mg with metals such as Nb is also attributed to reduced ionized impurity scattering. Recent experimental and theoretical studies challenge this view and favor the grain boundary (GB) scattering mechanism. A reduction of GB scattering improves the low-temperature performance of Mg3(Sb, Bi)2 alloys. However, it is still elusive how these metal additions reduce the GB resistivity. In this study, Nb-free and Nb-added Mg3Sb2 are studied through diffraction, X-ray absorption spectroscopy, solid-state nuclear magnetic resonance spectroscopy, and atom probe tomography. It is shown that Nb does not enter the Mg3Sb2 matrix and remains in the metallic state. Besides, Nb diffuses along the GB forming a wetting layer, which modifies the interfacial energy and accelerates grain growth. The GB resistivity appears to be reduced by Nb-enrichment, as evidenced by modeling the electrical transport properties. This study not only confirms the GB scattering in Mg3Sb2 but also reveals the hitherto hidden role of metallic additives on enhancing grain growth and reducing the GB resistivity.
AB - The poor carrier mobility of polycrystalline Mg3Sb2 at low temperatures strongly degrades the thermoelectric performance. Ionized impurities are initially thought to dominate charge carrier scattering at low temperatures. Accordingly, the increased electrical conductivity by replacing Mg with metals such as Nb is also attributed to reduced ionized impurity scattering. Recent experimental and theoretical studies challenge this view and favor the grain boundary (GB) scattering mechanism. A reduction of GB scattering improves the low-temperature performance of Mg3(Sb, Bi)2 alloys. However, it is still elusive how these metal additions reduce the GB resistivity. In this study, Nb-free and Nb-added Mg3Sb2 are studied through diffraction, X-ray absorption spectroscopy, solid-state nuclear magnetic resonance spectroscopy, and atom probe tomography. It is shown that Nb does not enter the Mg3Sb2 matrix and remains in the metallic state. Besides, Nb diffuses along the GB forming a wetting layer, which modifies the interfacial energy and accelerates grain growth. The GB resistivity appears to be reduced by Nb-enrichment, as evidenced by modeling the electrical transport properties. This study not only confirms the GB scattering in Mg3Sb2 but also reveals the hitherto hidden role of metallic additives on enhancing grain growth and reducing the GB resistivity.
KW - Mg Sb
KW - comprehensive microscopy
KW - grain boundary scattering
KW - ionized impurity scattering
KW - thermoelectric
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U2 - 10.1002/adfm.202100258
DO - 10.1002/adfm.202100258
M3 - Article
AN - SCOPUS:85105132459
VL - 31
JO - Advanced Functional Materials
JF - Advanced Functional Materials
SN - 1616-301X
IS - 28
M1 - 2100258
ER -