Synthesis, Structure, and Thermoelectric Properties of Barium Copper Polychalcogenides with Chalcogen-Centered Cu Clusters and Te22– Dumbbells


  • Dedicated to Professor John D. Corbett on the occasion of his 85th birthday


BaCu6–xSTe6 and BaCu6–xSe1–yTe6+y were synthesized from the elements at 663 K. These chalcogenides adopt a new structure type, cubic space group Pmequation image, with a = 6.9680(2) Å in the case of BaCu5.93SeTe6. Therein, the Cu atoms form cubic clusters, centered by Se atoms, where statistically 2.07 corners are unoccupied. All Te atoms are part of Te22– dumbbells, leading to a charge-balanced formula when x = 0: Ba2+(Cu+)6Se2–(Te22–)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 Te22– pairs. Band structure calculations on different BaCu6SeTe6 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 BaCu5.7Se0.6Te6.4.