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Materials 2018, 11(5), 773; https://doi.org/10.3390/ma11050773

The Effects of Excess Co on the Phase Composition and Thermoelectric Properties of Half-Heusler NbCoSb

1
Key Laboratory of Fluid and Power Machinery of Ministry of Education, School of Materials Science & Engineering, Xihua University, Chengdu 610039, China
2
Institute for Metallic Materials, IFW-Dresden, 01069 Dresden, Germany
3
Department of Physics and TcSUH, University of Houston, Houston, TX 77204, USA
*
Authors to whom correspondence should be addressed.
Received: 12 April 2018 / Revised: 4 May 2018 / Accepted: 9 May 2018 / Published: 11 May 2018
(This article belongs to the Special Issue Energetic Materials and Processes)
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Abstract

NbCoSb with nominal 19 valence electrons, and is supposed to be metallic, has recently been reported to also exhibit the thermoelectric properties of a heavily doped n-type semiconductor. In this study, we prepared Co-rich NbCo1+xSb samples (x = 0, 0.2, 0.3, 0.4, 0.5), and their phase compositions, microstructures and thermoelectric properties were investigated. The Seebeck coefficient increased a great deal with increasing x, due to decreasing carrier concentration, and the total thermal conductivity reduced mainly because of declining κe. Finally, a peak thermoelectric figure of merit, ZT, was about 0.46 for NbCo1.3Sb at 973 K. This enhancement was mainly attributed to the reduction of electric thermal conductivity and the increase of Seebeck coefficient. The excess Co had effects on the carrier concentration, deformation potential Edef and DOS effective mass m*. Adding an excessive amount of Co leads to a very high Edef, which was detrimental for transport characteristics. View Full-Text
Keywords: half-Heusler; NbCoSb; excess Co; thermoelectric performance half-Heusler; NbCoSb; excess Co; thermoelectric performance
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Huang, L.; Wang, J.; Chen, X.; He, R.; Shuai, J.; Zhang, J.; Zhang, Q.; Ren, Z. The Effects of Excess Co on the Phase Composition and Thermoelectric Properties of Half-Heusler NbCoSb. Materials 2018, 11, 773.

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