Thermoelectric performance of indium-rich thiospinels [formula omitted] ([formula omitted] ≈ 0.16, 0.22 and x ≈ 0.1, 0.2).
In: Journal of Alloys & Compounds, Jg. 976 (2024-03-05), S. N.PAG
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Powder x-ray diffraction and Raman spectroscopy studies showed In-rich thiospinels with the chemical formula In 1 − y □ y In 2 S 4 − x Te x (y ≈ 0.16, 0.22 and x ≈ 0.1, 0.2) to be composed of the cubic α -modification [space group (SG) Fd 3 ̅ m ] with a minor admixture of tetragonal β -phase (SG I 4 1 / amd). Tellurium incorporation in the crystal structures is confirmed by Rietveld refinements, energy dispersive x-ray- and Raman spectroscopies. All samples are found to be indirect band gap semiconductors with an E g opt ≈ 2 eV, which decreases with increasing Te-content. The thiospinels with y ≈ 0.16, 0.22 and x ≈ 0.1 revealed by two orders of magnitude enhanced charge carrier concentration (i.e., n ≈ 1018 cm−3) and ≈ 6–9 times larger charge carrier mobilities (μ) than corresponding binary specimens. A kink at 200 K in ρ T is found to originate from a stepper increase of n. The Seebeck coefficient is negative for all samples indicating electrons to be the dominant charge carriers. The total thermal conductivity of the compounds is almost completely phonon (κ ph) mediated. The Debye-Callaway fits of κ ph reveal an enhanced point-defect scattering in the In 2.78 S 4 − x Te x series compared to In 2.84 S 4 − x Te x , in accordance with the higher vacancy concentration (i.e., smaller y). The Balkanski-Klemens analysis of the temperature dependent Raman shifts indicated domination of three-phonon scattering mechanism agreeing with the lowered κ ph values. The appearance of low-energy optical modes confirms the In1-atoms, randomly occupying [In1S 4 ]-tetrahedra, to reveal a 'rattling' motion and thus, to be a probable source of enhanced anharmonic effects limiting κ ph. Te-doping of In-rich thiospinels (y ≈ 0.16, 0.22) results in the improvement of the electrical transport characteristics and simultaneously in an increase of their thermal conductivities due to smaller vacancy concentration. The possible reduction of κ ph and the improvement of the TE performance are discussed. • The In 1 − y □ y In 2 S 4 − x Te x (y ≈ 0.16, 0.22 and x ≈ 0.1, 0.2) thiospinels were synthesized and characterized. • All compounds are indirect band-gap semiconductors with an E g opt ≈ 2 eV. • Te-doping enhances charge carrier concentration and mobilities as well as improves thermoelectric power factors. • Thermal conductivities are related to the vacancy concentration y and is mainly due to three-phonon scattering processes. • All these indicate improved thermoelectric efficiency in comparison with undoped binary In-thiospinels. [ABSTRACT FROM AUTHOR]
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Thermoelectric performance of indium-rich thiospinels [formula omitted] ([formula omitted] ≈ 0.16, 0.22 and x ≈ 0.1, 0.2).
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Autor/in / Beteiligte Person: | Zuñiga-Puelles, Esteban ; Özden, Ayberk ; Pacheco, Vicente ; Akselrud, Lev ; Cardoso-Gil, Raul ; Straßheim, André ; Wyżga, Paweł ; Himcinschi, Cameliu ; Gumeniuk, Roman |
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Zeitschrift: | Journal of Alloys & Compounds, Jg. 976 (2024-03-05), S. N.PAG |
Veröffentlichung: | 2024 |
Medientyp: | academicJournal |
ISSN: | 0925-8388 (print) |
DOI: | 10.1016/j.jallcom.2023.173055 |
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