Toppling the Transport Properties with Cationic Overstoichiometry in Thermoelectric Colusite: [Cu<sub>26</sub>Cr<sub>2</sub>Ge<sub>6</sub>]<sub>1+δ</sub>S<sub>32</sub>
Gabin Guélou, Ventrapati Pavan Kumar, Abdelhamid Bourhim, Pierric Lemoine, B. Raveau, Andrew Supka, Oleg I. Lebedev, Rabih Al Rahal Al Orabi, Marco Fornari, Koichiro Suekuni, Emmanuel Guilmeau
Abstract
The excellent thermoelectric properties of colusite are known to be closely related to the nature of the cations at the core of the tetrahedral–octahedral complexes. Here, we demonstrate that cation overstoichiometry decreases the carrier concentration and also generates structural disorder, which modify the conduction mechanism in a way that resembles the effect of cation-size mismatch. This functionalization of the “Cu26S32” conductive network leads to a high figure of merit of 1.0 at 700 K. This study highlights the importance of the cationic arrangement and furthers our understanding on the fascinating transport properties in colusite.