[15p-A35-1~16] 9.4 Thermoelectric conversion

▲ [15p-A35-12] Synthesis and thermoelectric properties of quaternary Si clathrate K_8-δGa_xZn_ySi_46-x-y

〇(PC)Shiva Kumar Singh¹, Motoharu Imai¹ (1.NIMS, Tsukuba, Japan)

Keywords:Clathrate silicides, Thermoelectric, Intermetallic

Group 14 clathrates have received significant attention as functional materials such as thermoelectric and photovoltaic materials [1-4]. In this study, we synthesized quaternary Si clathrate K₈Ga_xZn_ySi_46-x-y and investigated their thermoelectric properties. By systematically substituting trivalent Ga atom with divalent Zn atom, we change the average valence of Ga_xZn_y in the clathrate cage framework and see its effects on the thermoelectric properties. X-ray diffraction patterns confirm synthesis of clathrate although it contain a trace of secondary phase Si. Spark plasma sintering was carried out to obtain compact specimens for compositional and physical property characterizations. Electron probe micro-analysis confirmed formation of ternary and quaternary phase clathrate. K_7.7Zn_3.2Si_43.0 and K_7.6Ga_5.8Zn_0.8Si_39.6 show metallic conduction and the other samples depict semiconducting conduction. The Seebeck coefficient of all the samples is negative, indicating that dominant carriers are electrons. Maximum ZT obtained for sample K_7.6Ga_5.8Zn_0.8Si_39.6 was 0.01 at 320 K.
References:
[1] The Physics and Chemistry of Inorganic Clathrates, Ed. G.S.Nolas (Springer, Heidelberg, 2014)
[2] T. Takabatake et al., Rev. Mod. Phys. 86, (2014) 669.
[3] S. K. Singh et al. Jpn. J. Appl. Phys. 54 (2015) 091801.
[4] Y. He et al. Energy Environ. Sci. 7 (2014) 2598.