Chalcopyrite ZnSnSb_2: A Promising Thermoelectric Material

Abstract

Ternary compounds with a tetragonal chalcopyrite structure, such as CuGaTe2, are promising thermoelectric (TE) materials. It has been demonstrated in various chalcopyrite systems, including compounds with quaternary chalcopyrite-like structures, that the lattice parameter ratio, c/a, being exactly 2.00 to have a pseudo-cubic structure is key to increase the degeneracy at the valence band edge and ultimately achieve high TE performance. Considering the fact that ZnSnSb_2 with a chalcopyrite structure is reported to have c/a close to 2.00, it is expected to have multiple valence bands leading to a high p-type zT. However, there are no complete investigations on the high temperature TE properties of ZnSnSb_2 mainly because of the difficulty of obtaining a single-phase ZnSnSb_2. In the present study, pure ZnSnSb_2 samples with no impurities are synthesized successfully using a Sn flux-based method and TE properties are characterized up to 585 K. Transport properties and thermal analysis indicate that the structure of ZnSnSb_2 remains chalcopyrite with no order–disorder transition and clearly show that ZnSnSb_2 can be made to exhibit a high zT in the low-to-mid temperature range through further optimization.