Half-Heusler phase TmNiSb under pressure: intrinsic phase separation, thermoelectric performance and structural transition

Half-Heusler phase TmNiSb under pressure: intrinsic phase separation, thermoelectric performance and structural transition

Half-Heusler (HH) phase TmNiSb was obtained by arc-melting combined with high-pressure high-temperature sintering in conditions: p = 5.5 GPa, T HPHT = 20, 250, 500, 750, and 1000  ∘ C. Within pressing temperatures 20–750  ∘ C the samples maintained HH structure, however, we observed intrinsic phase...

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Bibliographic Details
Published in:Scientific reports Vol. 13; no. 1; p. 1592
Main Authors: Ciesielski, Kamil, Synoradzki, Karol, Szymański, Damian, Tobita, Kazuki, Berent, Katarzyna, Obstarczyk, Patryk, Kimura, Kaoru, Kaczorowski, Dariusz
Format: Journal Article
Language:English
Published: London Nature Publishing Group UK 28-01-2023
Nature Publishing Group
Nature Portfolio
Subjects:
639/301
639/301/119/1000
639/301/119/995
Conductivity
Diffraction
Electrical resistivity
Energy
Heat conductivity
High temperature
Humanities and Social Sciences
multidisciplinary
Nickel
Phase transitions
Science
Science (multidisciplinary)
Temperature
Thulium
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Summary:Half-Heusler (HH) phase TmNiSb was obtained by arc-melting combined with high-pressure high-temperature sintering in conditions: p = 5.5 GPa, T HPHT = 20, 250, 500, 750, and 1000  ∘ C. Within pressing temperatures 20–750  ∘ C the samples maintained HH structure, however, we observed intrinsic phase separation. The material divided into three phases: stoichiometric TmNiSb, nickel-deficient phase TmNi 1 - x Sb, and thulium-rich phase Tm(NiSb) 1 - y . For TmNiSb sample sintered at 1000  ∘ C, we report structural transition to LiGaGe-type structure ( P 6 3 mc , a = 4.367(3) Å, c = 7.138(7) Å). Interpretation of the transition is supported by X-ray powder diffraction, electron back-scattered diffraction, ab-initio calculations of Gibbs energy and phonon dispersion relations. Electrical resistivity measured for HH samples with phase separation shown non-degenerate behavior. Obtained energy gaps for HH samples were narrow ( ≤ 260 meV), while the average hole effective masses in range 0.8–2.5 m e . TmNiSb sample pressed at 750  ∘ C achieved the biggest power factor among the series, 13 μ WK - 2 cm - 1 , which proves that the intrinsic phase separation is not detrimental for the electronic transport.
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ISSN:2045-2322
2045-2322
DOI:10.1038/s41598-023-28110-4