The effect of simultaneous substitution on the electronic band structure and thermoelectric properties of Se-doped Co3SnInS2 with the Kagome lattice

• Se doped Co3SnInS1−ySey with a Kagome lattice was synthesized using a solid state reaction method.
• The Se doping induces a decrease in resistivity without the suppression of the Seebeck coefficient due to the disordering of the Sn site preference.
• Assuming a strong Sn site preference, DFT calculations indicate that Se doping does not contribute Se orbital levels at the Fermi level.

The thermoelectric properties and electronic band structures for Se-doped Co3SnInS2 were examined. The parent compound of this material (Co3Sn2S2) has two kinds of Sn sites (Sn1 and Sn2 sites). The density functional theory (DFT) calculations show that the indium substitution at the Sn2 site induces a metallic band structure, on the other hand, a semiconducting band structure is obtained from substitution at the Sn1 site. However, according to the previous reports, since the indium atom prefers to replace the tin atom at the Sn1 site rather than the Sn2 site, the resistivity of Co3SnInS2 shows semiconducting-like behavior. In this study we have demonstrated that metallic behavior and a decrease in resistivity for Se-doped Co3SnInS2 occurs without suppression of the Seebeck coefficient. From the DFT calculations, when the selenium content is above 0.5, the total crystallographic energy shows that a higher indium occupancy at Sn2 site is more stable. Therefore, it is suggested that the selenium doping suppress the site preference for indium substitution. This is one of the possible explanations for the metallic conductivity observed in Se-doped Co3SnInS2

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