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

Abstract

Inspired by the high figure-of-merit, zT, of β-Cu₂Se at elevated temperatures, the thermoelectric properties of the hot-pressed sulphide–tellurides Ba₃Cu_16−x(S,Te)₁₁ were studied. These materials crystallize in a rhombohedral structure, space group Rm. Hot-pressed Ba₃Cu_15.3S_7.5Te_3.5 has the highest power factor, 4.6 μW cm⁻¹ K⁻², which is almost 50% higher than that of the best cold-pressed sample, Ba₃Cu₁₆S₉Te₂ with 2.4 μW 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 β-Cu₂Se with high zT values renders them more feasible for thermoelectric devices. Among the three studied materials, the one with the highest Te content, Ba₃Cu_15.3S_7.5Te_3.5, exhibits the lowest thermal conductivity and the highest electrical conductivity, which results in zT = 0.88 at 745 K.