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A4: Theory - bulk materials

Study of fluctuation for Ga distribution in Sn clathrate Ba8Ga16Sn30 by Monte-Carlo method 

K. Matsumoto, K. Akai, K. Kishimoto, H. Kurisu, T. Koyanagi, S. Yamamoto
Yamaguchi Univ.

Tin semiconducting clathrate Ba8Ga16Sn30 (BGS) is a candidate of high performance thermoelectric materials with ZT~1 in the middle temperature range. [1,2] The clathrates have a host-guest structure, and then the host structure is composed of Ga and Sn atoms. Those Ga and Sn atoms are randomly positioning in the host lattice, and the randomness in the host lattice causes the alloy scattering for carriers. Therefore lowering of the carrier mobility by the alloy scattering is worried in semiconducting clathrates. In the present study, we calculate the Ga distribution in the host lattice of BGS. It is the first step to discuss the scattering effect of carrier in BGS. To calculate Ga distribution in the lattice, we take accounting of electrostatic forces between Ba, Ga atoms. The calculated result shows that the spatial fluctuation of the number of Ga par unit cells is about one, which is 1/3 for the perfectly random case. But the magnitude is large for carrier transports.

[1] Deng et al. JAP 108 (2010) 073705.

[2] Saiga et al., J. Alloy. Compd. 537(2012) 303.