TY - JOUR
T1 - Low thermal conductivity and promising thermoelectric performance in A: XCoSb (A = V, Nb or Ta) half-Heuslers with inherent vacancies
AU - Ferluccio, Daniella A.
AU - Halpin, John E.
AU - Macintosh, Kathryn L.
AU - Quinn, Robert J.
AU - Don, Eric
AU - Smith, Ronald I.
AU - Maclaren, Donald A.
AU - Bos, Jan Willem G.
N1 - Funding Information:
The EPSRC is acknowledged for funding the research on half-Heusler thermoelectrics and instrumentation (EP/N01717X/1, EP/N017218/1 and EP/P001483/1) and for a studentship for DAF. The STFC is acknowledged for allocation of neutron scattering beamtime at the ISIS facility (RB1810470 and Xpress 1890125). Raw data upon with this publication is based can be accessed at http://dx.doi.org/10.5525/gla.researchdata.753.
Publisher Copyright:
© 2019 The Royal Society of Chemistry.
Open Access Article. This article is licensed under a Creative Commons Attribution 3.0 Unported Licence
The author was not affiliated to SAMS at the time of publication.
PY - 2019/3/13
Y1 - 2019/3/13
N2 - 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.
AB - 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.
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U2 - 10.1039/c9tc00743a
DO - 10.1039/c9tc00743a
M3 - Article
AN - SCOPUS:85066949576
SN - 2050-7534
VL - 7
SP - 6539
EP - 6547
JO - Journal of Materials Chemistry C
JF - Journal of Materials Chemistry C
IS - 22
ER -