| Autor: |
Ferluccio, Daniella A., Halpin, John E., MacIntosh, Kathryn L., Quinn, Robert J., Don, Eric, Smith, Ronald I., MacLaren, Donald A., Bos, Jan-Willem G. |
| Zdroj: |
Journal of Materials Chemistry C; 6/14/2019, Vol. 7 Issue 22, p6539-6547, 9p |
| Abstrakt: |
Half-Heuslers with vacancies that are stabilised by a semiconducting electron count offer new opportunities for discovering good thermoelectric performance. Here, we present a comparative study of AxCoSb half-Heuslers (A = V, Nb or Ta) with intrinsic vacancies. Structural analysis reveals an increasing vacancy concentration from V (13%) to Nb (15%) to Ta (19%) with evidence for ∼3% V/Co inversion. This decrease in ability to n-type dope these materials is caused by an increase in conduction band dispersion, evident from a decreasing density of states mass from Hall data, leading to a higher cost of populating these antibonding states. V0.87CoSb has an ultralow lattice thermal conductivity, κlat∼ 2.2 W m−1 K−1, which cannot be explained within the Callaway framework. Coupled to a promising power factor, S2/ρ = 2.25 mW m−1 K−2, this results in ZT = 0.6 at 950 K. Nb0.85CoSb has a power factor of S2/ρ = 2.75 mW m−1 K−2 with κ∼ 4.75 W m−1 K−1, yielding a similar ZT = 0.5 at 950 K. Ta0.81CoSb has a microstructure consisting of smaller grains than the other samples, impacting both the carrier and thermal transport, yielding a power factor S2/ρ = 0.75 mW m−1 K−2 and ZT = 0.3 at 950 K. The ultralow κlat for V0.87CoSb may be linked to porosity effects that do not strongly impact on the charge transport, thus affording a new route towards improved performance. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
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