Synthesis, Structure, and Thermoelectric Properties of Barium Copper Polychalcogenides with Chalcogen‐Centered Cu Clusters and Te₂^2– Dumbbells

Abstract

Abstract BaCu 6– x STe 6 and BaCu 6– x Se 1– y Te 6+ y were synthesized from the elements at 663 K. These chalcogenides adopt a new structure type, cubic space group Pm $\bar {3}$ , with a = 6.9680(2) Å in the case of BaCu 5.93 SeTe 6 . Therein, the Cu atoms form cubic clusters, centered by Se atoms, where statistically 2.07 corners are unoccupied. All Te atoms are part of Te 2 2– dumbbells, leading to a charge‐balanced formula when x = 0: Ba 2+ (Cu + ) 6 Se 2– (Te 2 2– ) 3 . While Te atoms can be incorporated on the Se site, no evidence was found for the ability of Se atoms to replace Te in the Te 2 2– pairs. Band structure calculations on different BaCu 6 SeTe 6 models revealed a very small band gap at the Fermi level; all these chalcogenides with x > 0 should thus be p ‐doped semiconductors, which we experimentally confirmed for BaCu 5.7 Se 0.6 Te 6.4 .