Excellent ZT achieved in Cu1.8S thermoelectric alloys through introducing rare-earth trichlorides

Abstract

Digenite (Cu_1.8S) as a potential p-type thermoelectric (TE) material has attracted extensive attention due to its environmental-friendliness and low toxicity. However, there is always a trade-off between electrical transport properties and thermal conductivity to achieve a higher ZT in this system. In this work, the power factor and thermal conductivity of a series of rare-earth trichloride RECl₃ (RE = Y, La, Pr, Nd, Ce) doped Cu_1.8S samples were synergistically optimized by tailoring the band structure and introducing nanoprecipitates. Both DFT calculations and experimental results reveal that LaCl₃ doping could decrease the carrier concentration and enlarge the band gap to enhance the Seebeck coefficient and introduce LaCu₆ nanoprecipitates to reduce thermal conductivity, thus resulting in an enhanced ZT value of 1.2 in the 2 wt% LaCl₃ doped Cu_1.8S sample at 773 K, which is so far the highest ZT value in thermoelectric sulfides.