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2020
Journal Article
Titel
Thermoelectric properties of n-type half-Heusler NbCoSn with heavy-element Pt substitution
Abstract
Half-Heusler compounds with a valence electron count of 18, including ZrNiSn, ZrCoSb, and NbFeSb, are good thermoelectric materials owing to favorable electronic structures. Previous computational studies had predicted a high electrical power factor in another half-Heusler compound NbCoSn, but it has not been extensively investigated experimentally. Herein, the synthesis, structural characterization, and thermoelectric properties of the heavy-element Pt-substituted NbCoSn compounds are reported. Pt is found to be an effective substitute enabling the optimization of electrical power factor and simultaneously leading to a strong point defect scattering of phonons and the suppression of lattice thermal conductivity. Post-annealing significantly improves the carrier mobility, which is ascribed to the decreased grain boundary scattering of electrons. As a result, a maximum power factor of ∼3.4 mW m−1 K−2 is obtained at 600 K. In conjunction with the reduced lattice thermal conductivity, a maximum figure of merit zT of ∼0.6 is achieved at 773 K for the post-annealed NbCo0.95Pt0.05Sn, an increase of 100% compared to that of NbCoSn. This work highlights the important roles that the dopant element and microstructure play in the thermoelectric properties of half-Heusler compounds.
Author(s)
Tags
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annealing
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chemical element
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cobalt alloys
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computational studies
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crystal lattices
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electric power factor
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electronic structure
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grain boundary
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grain boundary scattering
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Half-Heusler compound
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hall mobility
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high electrical power
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hole mobility
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iron alloys
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lattice thermal conductivity
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niobium alloy
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platinum compounds
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structural characterization
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ternary alloy
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thermal conductivity
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thermoelectric equipment
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thermo-electric materials
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thermoelectric properties
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thermoelectricity
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tin alloys
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Zircaloy