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

Abstract

Chemical substitution in Co₃Sn_2−xIn_xS₂ (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 μW cm⁻¹ K⁻²) is found for x = 0.85, which corresponds to ZT ≈ 0.2 at 300 K.