High thermoelectric performance of Ba3Cu16-x(S,Te)11

Inspired by the high figure-of-merit, zT, of -Cu2Se at elevated temperatures, the thermoelectric properties of the hot-pressed sulphide-tellurides Ba3Cu16-x(S,Te)(11) were studied. These materials crystallize in a rhombohedral structure, space group R3m. Hot-pressed Ba3Cu15.3S7.5Te3.5 has the highest power factor, 4.6 W cm(-1) K-2, which is almost 50% higher than that of the best cold-pressed sample, Ba3Cu16S9Te2 with 2.4 W cm(-1) K-2 at 700 K. These quaternary sulphide-tellurides are bestowed with an extraordinarily low total thermal conductivity, which is below 0.6 W m(-1) K-1 throughout the entire studied temperature range. In addition, their higher stability at elevated temperatures compared to Cu2S and -Cu2Se with high zT values renders them more feasible for thermoelectric devices. Among the three studied materials, the one with the highest Te content, Ba3Cu15.3S7.5Te3.5, exhibits the lowest thermal conductivity and the highest electrical conductivity, which results in zT = 0.88 at 745 K.