posted on 2019-11-14, 14:40authored byIlaria Siloi, Priya Gopal, Stefano Curtarolo, Marco Buongiorno Nardelli, Paz Vaqueiro, Marco Fornari
Synthetic copper sulfides have emerged as promising nontoxic
and
low-cost materials for thermoelectric power generation in low-grade
waste heat recovery systems. Similarly to tetrahedrite and colusite,
mawsonite Cu6Fe2SnS8 exhibits a modified
corner sharing Cu–S tetrahedral network which usually leads
to p-type character and low thermal conductivity. In order to explore
the applicative potential of mawsonite, we studied the band structure,
the phonon dispersions, the electronic and transport coefficients,
as well as the effect of isovalent substitutions of Fe, Sn, and S.
The combined analysis of electronic and vibrational properties highlights
the role of the weakly bonded copper component in achieving a very
low thermal conductivity. We also demonstrate that the Cu–S
bond builds a 2D conductive network where the contribution from other
elements is negligible. Magnetic calculations point to an antiferromagnetic
ground state substantially affected by the covalency of the bonds
with the conductive plane. The chemical substitution of Fe with Ni
leads to nonmagnetic metals whereas Cu6Fe2SnSe8, Cu6Fe2PbS8, and Cu6Fe2GeX8 with X = S, Se, and Te are semiconductors.