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Phase Formation Behavior and Thermoelectric Transport Properties of S-Doped FeSe2−xSx Polycrystalline Alloys

Authors :
Okmin Park
Se Woong Lee
Sang Jeong Park
Sang-il Kim
Source :
Micromachines, Vol 13, Iss 12, p 2066 (2022)
Publication Year :
2022
Publisher :
MDPI AG, 2022.

Abstract

Some transition-metal dichalcogenides have been actively studied recently owing to their potential for use as thermoelectric materials due to their superior electronic transport properties. Iron-based chalcogenides, FeTe2, FeSe2 and FeS2, are narrow bandgap (~1 eV) semiconductors that could be considered as cost-effective thermoelectric materials. Herein, the thermoelectric and electrical transport properties FeSe2–FeS2 system are investigated. A series of polycrystalline samples of the nominal composition of FeSe2−xSx (x = 0, 0.2, 0.4, 0.6, and 0.8) samples are synthesized by a conventional solid-state reaction. A single orthorhombic phase of FeSe2 is successfully synthesized for x = 0, 0.2, and 0.4, while secondary phases (Fe7S8 or FeS2) are identified as well for x = 0.6 and 0.8. The lattice parameters gradually decrease gradually with S content increase to x = 0.6, suggesting that S atoms are successfully substituted at the Se sites in the FeSe2 orthorhombic crystal structure. The electrical conductivity increases gradually with the S content, whereas the positive Seebeck coefficient decreases gradually with the S content at 300 K. The maximum power factor of 0.55 mW/mK2 at 600 K was seen for x = 0.2, which is a 10% increase compared to the pristine FeSe2 sample. Interestingly, the total thermal conductivity at 300 K of 7.96 W/mK (x = 0) decreases gradually and significantly to 2.58 W/mK for x = 0.6 owing to the point-defect phonon scattering by the partial substitution of S atoms at the Se site. As a result, a maximum thermoelectric figure of merit of 0.079 is obtained for the FeSe1.8S0.2 (x = 0.2) sample at 600 K, which is 18% higher than that of the pristine FeSe2 sample.

Details

Language :
English
ISSN :
2072666X
Volume :
13
Issue :
12
Database :
Directory of Open Access Journals
Journal :
Micromachines
Publication Type :
Academic Journal
Accession number :
edsdoj.9ac12552125943fcbe86f8b980bf53b3
Document Type :
article
Full Text :
https://doi.org/10.3390/mi13122066