Park Okmin, Lee Se Woong, Park Sang Jeong, Kim Sang-Il
Department of Materials Science and Engineering, University of Seoul, Seoul 02504, Republic of Korea.
Micromachines (Basel). 2022 Nov 25;13(12):2066. doi: 10.3390/mi13122066.
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, FeTe, FeSe and FeS, are narrow bandgap (~1 eV) semiconductors that could be considered as cost-effective thermoelectric materials. Herein, the thermoelectric and electrical transport properties FeSe-FeS system are investigated. A series of polycrystalline samples of the nominal composition of FeSeS ( = 0, 0.2, 0.4, 0.6, and 0.8) samples are synthesized by a conventional solid-state reaction. A single orthorhombic phase of FeSe is successfully synthesized for = 0, 0.2, and 0.4, while secondary phases (FeS or FeS) are identified as well for = 0.6 and 0.8. The lattice parameters gradually decrease gradually with S content increase to = 0.6, suggesting that S atoms are successfully substituted at the Se sites in the FeSe 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/mK at 600 K was seen for = 0.2, which is a 10% increase compared to the pristine FeSe sample. Interestingly, the total thermal conductivity at 300 K of 7.96 W/mK ( = 0) decreases gradually and significantly to 2.58 W/mK for = 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 FeSeS ( = 0.2) sample at 600 K, which is 18% higher than that of the pristine FeSe sample.
由于某些过渡金属二硫属化物具有优异的电子传输特性，有望用作热电材料，因此近年来受到了广泛研究。铁基硫属化物，如FeTe、FeSe和FeS，是窄带隙（约1 eV）半导体，可被视为具有成本效益的热电材料。在此，对FeSe - FeS体系的热电和电输运性质进行了研究。通过传统的固态反应合成了一系列标称组成为FeSeS（x = 0、0.2、0.4、0.6和0.8）的多晶样品。当x = 0、0.2和0.4时，成功合成了单一正交相的FeSe，而当x = 0.6和0.8时，也鉴定出了次生相（FeS或FeS₂）。随着S含量增加到x = 0.6，晶格参数逐渐减小，这表明S原子成功地取代了FeSe正交晶体结构中的Se位点。在300 K时，电导率随S含量逐渐增加，而正塞贝克系数随S含量逐渐减小。对于x = 0.2的样品，在600 K时最大功率因数为0.55 mW/mK²，与原始FeSe样品相比提高了10%。有趣的是，由于S原子在Se位点的部分取代导致点缺陷声子散射，300 K时原始FeSe样品的总热导率7.96 W/mK（x = 0）逐渐显著降低至x = 0.6时的2.58 W/mK。结果，FeSeS（x = 0.2）样品在600 K时获得了最大热电优值0.079，比原始FeSe样品高18%。
