Thermoelectric Properties of Two-Phases Alloys of Type-I Ge clathrates

Type-I Ge clathrate 2상 합금의 열전특성

Thermoelectric properties and microstructures of $Sr_{8-x}Ba_xGA_{16}Ge_{30}$ alloys fabricated by the arc-melting method were investigated. The alloys with the nominal composition of $Sr_8Ga_{16}Ge_{30}$ and $Ba_8Ga_{16}Ge_{30}$ were the single-phase alloys, while those of $Sr_4Ba_4Ga_{16}Ge_{30}$ and $Sr_2Ba_6Ga_{16}Ge_{30}$ were two-phases alloys. Electrical resistivity and the Seebeck coefficient for both two-phases alloys were higher in magnitude than those of the single-phase alloys between room temperature and 873K The thermal conductivities for both two-phase alloys were reduced with respect to those of the single-phase alloys in the whole temperature range. The maximum values of ZT for $Sr_4Ba_4Ga_{16}Ge_{30}$ and $Sr_2Ba_6Ga_{16}Ge_{30}$ were achieved with the values of 0.69 at 753K and 0.51 at 754K, respectively, while those of $Sr_8Ga_{16}Ge_{30}$ and $Ba_8Ga_{16}Ge_{30}$ were 0.86 at 758K and 0.76 at 943K, respectively.