Thermoelectric properties of superionic Li_0.11Cu_1.89S compound

Copper sulfide is a multifunctional material. Copper sulfides are known to be used in photo-electric converters, in plasmonics, in active electrodes of batteries and supercapacitors, etc. The excellent thermoelectric properties of copper sulfide are well-known too. The purpose of this study is to investigate the thermoelectric performance of nanocomposite copper sulfide contained monoclinic Cu₂S and tetragonal Cu_1.96S phase. According to scanning electron microscopy, the average particle size of the synthesized powder was about 373 nm. The Li_0.11Cu_1.89S sample showed an electronic conductivity of 50-180 S/cm, a Seebeck coefficient of 0.04-0.31 mV/K in the range of 300-700 K, and high power factor 5.8 μW K^-2cm^-1 at 672 K. Total thermal conductivity decreases with increasing temperature from 0.61 to 0.22 W∙K^-1m^-1 in the range of 300-700 K. Such low thermal conductivity and high power factor made it possible to achieve an extremely high dimensionless thermoelectric figure of merit ZT = 1.76 at 672 K, which allows to consider the Li_0.11Cu_1.89S alloy as a promising thermoelectric material.