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

Digenite (Cu1.8S) 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 Cu1.8S 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 Cu1.8S sample at 773 K, which is so far the highest ZT value in thermoelectric sulfides.