Preparation and thermoelectric properties of sintered iodine-containing clathrate compounds Ge_(38)Sb_8I_8 and Sn_(38)Sb_8I_8

摘要

The iodine-containing cationic type-Ⅰ clathrates Ge_(38)Sb_8I_8 and Sn_(38)Sb_8I_8 were prepared and their thermodynamic properties as well as their thermoelectric properties were investigated. Their atomic displacement parameters were as large as those of anionic clathrates such as Ba_8Ga_(16)Ge_(30) and Cs_8Cd_4Sn_(42). The room temperature thermal conductivities of Ge_(38)Sb_8I_8 and Sn_(38)Sb_8I_8 were 7 and 12 mW cm~(-1) K~(-1), respectively; these values were as low as that of the above anionic clathrates. Both cationic clathrates had negative Seebeck coefficients; the band gap energies of Ge_(38)Sb_8I_8 and Sn_(38)Sb_8I_8 were 1.16 and 0.80 eV, respectively.