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▲ [19p-P13-6] Synthesis of clathrate K8Gax-yAlySi46-x-y with enhanced thermoelectric property
キーワード：Silicides,Clathrate,Thermoelectric
Inorganic clathrates are excellent candidate for high-performance functional materials in various applications such as thermoelectrics and photovoltaics [1-3]. We report here synthesis and thermoelectric properties of polycrystalline clathrates K8Gax-yAlySi46-x-y. X-ray diffraction patterns indicated that the products are the target phases and contain only a trace level of secondary phase. Spark plasma sintering was carried out to obtain dense specimens for compositional and physical property characterizations. Chemical compositions of the spark plasma sintered products determined using electron probe micro-analysis were found to be K7.6(1)Ga7.9(4)Si39.9(6) (KGaSi), K7.6(1)Ga4.9(1)Al3.0(8)Si39.4(8) (KGaAlSi), and K7.6(1)Al7.0(4)Si39.3(2) (KAlSi). Electrical conductivity measurement below 320 K indicated semiconducting behavior for KGaSi and KGaAlSi samples and metallic behavior for KAlSi sample. Seebeck coefficient measurement confirmed n-type conduction for all the samples. Compared with the end phases KGaSi and KAlSi, almost two-fold enhanced value of figure of merit (ZT) was obtained for the intermediate compound KGaAlSi. With respect to KGaSi, improved electrical conductivity and reduced thermal conductivity along with slightly decreased Seebeck coefficient are responsible for the enhancement of the ZT in KGaAlSi.