Enhanced Thermoelectric Performance in Hf-Free p-Type (Ti, Zr)CoSb Half-Heusler Alloys

Chauhan, Nagendra S.; Bathula, Sivaiah; Gahtori, Bhasker; Kolen’ko, Yury V.

doi:10.1007/s11664-019-07486-y

Cited by 32 publications

(25 citation statements)

References 39 publications

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“…Interestingly, κ is significantly lower and varies marginally in the measured temperature range, which can be ascribed to the defect chemistry and alloy scattering supplemented by mass and strain fluctuation, all of which synergistically enhance phonon scattering. The measured values for pristine VCoSb − and TiCoSb − HH alloys are comparable to previous reports. Upon annealing, the occurrence of spinodal decompositions further lowers the κ significantly for a wide temperature range, which is comparable to the κ obtained in bulk nanostructured ternary HH alloys.…”

Section: Resultssupporting

confidence: 90%

Low Lattice Thermal Conductivity in a Wider Temperature Range for Biphasic-Quaternary (Ti,V)CoSb Half-Heusler Alloys

Chauhan

Bhattacharjee

Maiti

et al. 2022

ACS Appl. Mater. Interfaces

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Intrinsically high lattice thermal conductivity has remained a major bottleneck for achieving a high thermoelectric figure of merit (zT) in state-of-the-art ternary half-Heusler (HH) alloys. In this work, we report a stable n-type biphasic-quaternary (Ti,V)CoSb HH alloy with a low lattice thermal conductivity κL ≈ 2 W m–1 K–1 within a wide temperature range (300–873 K), which is comparable to the reported nanostructured HH alloys. A solid-state transformation driven by spinodal decomposition upon annealing is observed in Ti0.5V0.5CoSb HH alloy, which remarkably enhances phonon scattering, while electrical properties correlate well with the altering electronic band structure and valence electron count (VEC). A maximum zT ≈ 0.4 (±0.05) at 873 K was attained by substantial lowering of κL and synergistic enhancement of the power factor. We perform first-principles density functional theory calculations to investigate the structure, stability, electronic structure, and transport properties of the synthesized alloy, which rationalize the reduction in the lattice thermal conductivity to the increase in anharmonicity due to the alloying. This study upholds the new possibilities of finding biphasic-quaternary HH compositions with intrinsically reduced κL for prospective thermoelectric applications.

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Section: Resultssupporting

confidence: 90%

Low Lattice Thermal Conductivity in a Wider Temperature Range for Biphasic-Quaternary (Ti,V)CoSb Half-Heusler Alloys

Chauhan

Bhattacharjee

Maiti

et al. 2022

ACS Appl. Mater. Interfaces

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“…However, their intrinsically high lattice thermal conductivity (κ L ) limits the ZT, thus hindering their commercial viability. To date, the highest TE figure-of-merit (ZT) of ∼ 1.5 at 700 K has been reported in the n-type HH alloy, Sb-doped Hf 0.25 Zr 0.25 Ti 0.5 NiSn. , Since then, efforts aimed toward ZT enhancement in HH alloys have attained only a minimal success, as ZT > 1 was realized only in a few studies − and remained limited to < 1 for most of the HH alloys reported to date. − …”

Section: Introductionmentioning

confidence: 99%

Defect Engineering for Enhancement of Thermoelectric Performance of (Zr, Hf)NiSn-Based n-type Half-Heusler Alloys

et al. 2020

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Defect engineering of thermoelectric (TE) materials enables the alteration of their crystal lattice by creating an atomic-scale disorder, which can facilitate a synergistic modulation of the electrical and phonon transport, leading to the enhancement of their TE properties. This work employs a compositional nonstoichiometry strategy for manipulation of Nivacancies and Ni-interstitials through Ni-deficient and Ni-excess compositions of (Zr, Hf)Ni 1±x Sn-based half-Heusler (HH) alloys to realize a stateof-the-art TE figure-of-merit (ZT) of ∼1.4 at 873 K in 4 atomic % Ni-excess HH composition, which corresponds to a remarkable TE conversion efficiency of ∼12%, estimated using the cumulative temperature dependence model. These alloys are synthesized employing arc-melting followed by spark plasma sintering and are characterized for their phase, morphology, structure, and composition along with electrical and thermal transport properties to examine the implication of Niexcess and Ni-deficiency on the TE properties of the synthesized Zr 0.6 Hf 0.4 NiSn HH alloy. A significant enhancement (∼30%) of ZT is observed in the low doping limit of Ni-excess HH compositions over their stoichiometric counterpart due to Ni-interstitials and in situ full-Heusler precipitation, which enable a strong phonon scattering for a drastic reduction in lattice thermal conductivity and lead to an enhancement of ZT. However, Ni-deficient HH compositions exhibit a deterioration in the TE properties owing to the vacancy-induced bipolarity. The defect-mediated optimization of electrical and thermal transport, thus, opens up promising avenues for boosting the TE performance of HH alloys.

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“…[17][18][19][20][21][22][23] This is due to the remarkable electronic transport with high power factors exhibited by many of these 18 VEC alloys, which desirably can be formed with constituents within the realm of earth-abundant materials. [24][25][26][27][28][29][30][31] Having a ternary equiatomic XYZ composition, most HH alloys crystallize into a cubic crystal system [space group F% 43m (no. 216)] and host a rich variety of 3d, 4d, and 5d transition metal elements.…”

Section: Introductionmentioning

confidence: 99%

A mechanistic view of defect engineered VFeSb half-Heusler alloys

Chauhan

Miyazaki

2022

Mater. Adv.

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Enhanced Thermoelectric Performance in Hf-Free p-Type (Ti, Zr)CoSb Half-Heusler Alloys

Cited by 32 publications

References 39 publications

Low Lattice Thermal Conductivity in a Wider Temperature Range for Biphasic-Quaternary (Ti,V)CoSb Half-Heusler Alloys

Low Lattice Thermal Conductivity in a Wider Temperature Range for Biphasic-Quaternary (Ti,V)CoSb Half-Heusler Alloys

Defect Engineering for Enhancement of Thermoelectric Performance of (Zr, Hf)NiSn-Based n-type Half-Heusler Alloys

A mechanistic view of defect engineered VFeSb half-Heusler alloys

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