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A2: Medium temperature materials

Thermoelectric properties of CuFeS2 and Cu9Fe9S16 based alloys with high power factors at room temperature

Naohito Tsujii, Takao Mori, Yukihiro Isoda
National Institute for Materials Science, Tsukuba, Japan

Recently, we have reported that the chalcopyrite-based materials Cu1-xFe1+xS2 and Cu1-xZnxFeS2 exhibit a thermoelectric power factor of 1 mW/K2m at 300-400 K [1,2]. The high power-factor near room temperature is important for thermoelectric generation because a significant part of waste heat resides in this temperature range. Furthermore, the chalcopyrite-based alloys consist of environmentally-friendly and abundant elements. Hence, these alloys are attractive thermoelectric materials. One problem is their relatively high thermal conductivity of about 5-6 W/Km at 400 K [1]. Here we report thermoelectric properties of a related compound, Cu9Fe9S16, known as mooihoekite. The unit cell of Cu9Fe9S16 is twice as large as that of CuFeS2. Hence, a lower thermal conductivity can be expected. We have prepared a sintered sample of Cu9Fe9S16. Thermal conductivity at room temperature was found to be 2-3 W/Km, much smaller than that of chalcopyrite-based alloys. Therefore, the mooihoekite-based alloy can also make a promising thermoelectric material by optimizing carrier concentration.

[1] N. Tsujii and T. Mori, Appl. Phys. Exp. 6 (2013) 043001.

[2] N. Tsujii, T. Mori, and Y. Isoda, J. Elec. Mater. (2014) DOI: 10.1007/s11664-014-3072-y