Enhancement of thermoelectric properties in the Nb–Co–Sn half-Heusler/Heusler system through spontaneous inclusion of a coherent second phase

Journal Article · Sun Aug 21 00:00:00 EDT 2016 · Journal of Applied Physics

DOI:https://doi.org/10.1063/1.4961215· OSTI ID:22598866

Buffon, Malinda L. C.,; Verma, Nisha; Lamontagne, Leo; Pollock, Tresa M. ^[1]; Laurita, Geneva ^[2]; Ghadbeigi, Leila; Sparks, Taylor D. ^[3]; Lloyd, Demetrious L. ^[2]; Seshadri, Ram ^[1]

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1. Materials Department, University of California, Santa Barbara, California 93106 (United States)
2. Materials Research Laboratory, University of California, Santa Barbara, California 93106 (United States)
3. Materials Science and Engineering, University of Utah, Salt Lake City, Utah 84112 (United States)

Half-Heusler XYZ compounds with an 18 valence electron count are promising thermoelectric materials, being thermally and chemically stable, deriving from relatively earth-abundant components, and possessing appropriate electrical transport properties. The typical drawback with this family of compounds is their high thermal conductivity. A strategy for reducing thermal conductivity is through the inclusion of secondary phases designed to minimize negative impact on other properties. Here, we achieve this through the addition of excess Co to half-Heusler NbCoSn, which introduces precipitates of a semi-coherent NbCo{sub 2}Sn Heusler phase. A series of NbCo{sub 1+x}Sn materials are characterized here using X-ray and neutron diffraction studies and electron microscopy. Electrical and thermal transport measurements and electronic structure calculations are used to understand property evolution. We find that annealing has an important role to play in determining antisite ordering and properties. Antisite disorder in the as-prepared samples improves thermoelectric performance through the reduction of thermal conductivity, but annealing during the measurement degrades properties to resemble those of the annealed samples. Similar to the more widely studied TiNi{sub 1+x}Sn system, Co addition to the NbCoSn phase results in improved thermoelectric performance through a decrease in thermal conductivity which results in a 20% improvement in the thermoelectric figure of merit, zT.

• OSTI ID: 22598866
• Journal Information: Journal of Applied Physics, Vol. 120, Issue 7; Other Information: (c) 2016 Author(s); Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-8979
• Country of Publication: United States
• Language: English

Related Subjects

75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ANNEALING
ELECTRON MICROSCOPY
ELECTRONIC STRUCTURE
ELECTRONS
HEUSLER ALLOYS
NEUTRON DIFFRACTION
NEUTRONS
PERFORMANCE
PRECIPITATION
THERMAL CONDUCTIVITY
THERMOELECTRIC MATERIALS
THERMOELECTRIC PROPERTIES
VALENCE
X RADIATION
X-RAY DIFFRACTION