Insight into the preponderant role of the lattice size in Sn-based colusites for promoting a high power factor

We investigated the feasibility of the co-doping effect of zinc and chromium for copper and vanadium substitution, respectively, and reported the first successful Cr incorporation within the bulk Sn-based colusite structure. We demonstrated that this could be achieved by combining process and lattice engineering to open a small solubility window within this sterically restricted V site. The thermoelectric properties of the colusite Cu25ZnV2-xCrxSn6S32 (x = 0-0.5) have been examined on sintered ingots over the temperature range of 300-700 K. As a result, we achieved the highest average power factor ever reported for Sn-based colusites. For the first time, our findings point out a striking insight related to the lattice size effect and its contribution to the Seebeck coefficient of Sn-based colusites. All the experimental results were rationalized by theoretical calculations. Using this unique finding, we finally optimized the compound by hot-pressing treatment and reported a competitive zT value of 0.8 at 700 K for the sample Cu25ZnV1.75Cr0.25Sn6S32.