Co3M2S2 (M = Sn, In) shandites as tellurium-free thermoelectrics

Chemical substitution in Co3Sn2-xInxS2 (0 <= x <= 2) enables tuning of the Fermi level within narrow bands of Co d-states. This results in a compositionally induced double metal-semiconductor-metal transition and manipulation of the thermoelectric power factor. The maximum power factor (14 mu W cm(-1) K-2) is found for x = 0.85, which corresponds to ZT approximate to 0.2 at 300 K.