Toppling the Transport Properties with Cationic Overstoichiometry in Thermoelectric Colusite: [Cu 26 Cr 2 Ge 6 ] 1+δ S 32

International audienceThe 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