1211.4467 (Masaya Fujioka et al.)

The effect of simultaneous substitution for thermoelectric property of
shandite-type Co3Sn2-xInxS2-ySey    [PDF]

Masaya Fujioka, Taizo Sibuya, Junya Nakai, Keigo Yoshiyasu, Yoshihiko Takano, Yoichi Kamihara, Masanori Matoba

Thermoelectric properties and electronic band structures are examined for In- and Se-substituted shandite-type Co3Sn2S2 (Co3Sn2-xInxS2-ySey) focusing on x = 1. Thermoelectric properties of Co3SnInS2-ySey are gradually increased with increasing y, and dimensionless figure of merit for thermoelectric devices (ZT) reaches to 0.07 at 300 K for Co3SnInS1.2Se0.8. While temperature (T) dependences of resistivity ({\rho}) of Co3SnInS2-ySey changes from d{\rho}/dT < 0 (semiconducting) to d{\rho}/dT > 0 (metallic) between y = 0.4-0.6. In this material, two kinds of Sn sites have different In occupancies in accordance with the site preference. Whether Co3Sn2-xInxS2-ySey behaves as metallic or semiconducting depends on its In occupancy in two Sn sites. Density functional theory (DFT) calculations show that Se substitution induces the gradual disordering of the site preference. The behavior of resistivity changes to metallic over y > 0.6 are probably due to the disordering. The enhancement of the thermoelectric properties of Co3Sn2-xInxS2-ySey is caused by this indirect effect of Se substitution.

View original: http://arxiv.org/abs/1211.4467