Precious metal nanoparticles dispersing toward highly enhanced mechanical and thermoelectric properties of copper sulfides

Cu_1.8S (digenite), a copper sulfide with natural Cu deficiencies, possesses excellent conductivity, low-cost, as well as environmentally friendly features. It has thus recently attracted heightened attention. However, the thermoelectric performance of pristine Cu_1.8S is poor, and the related mechanical properties have not been deeply investigated, which hinders this material from becoming a candidate for commercial applications. This work proposes an effective approach to synergistically improve the comprehensive performance of polycrystalline Cu_1.8S-based bulk materials for use in practical applications. Cu_1.8S-xRu (x = 0.005, 0.01, 0.02) bulk composites were successfully fabricated by combining mechanical alloying and spark plasma sintering technology. Benefiting from the overall optimized power factor and thermal conductivity by the regulated carrier concentration and enhanced phonon scattering effect from the incorporation of multiscale lattice defects, a peak figure of merit of 1.0 at 773 K was achieved in the Cu_1.8S-1% Ru bulk specimen. In addition, the introduction of ruthenium could enhance the thermal stability of Cu_1.8S materials by suppress the Cu ions motion. A conversion efficiency of 1.0% at a temperature difference of 480 K was obtained for the single-leg TE module. Finally, the excellent average Vickers hardness of 1.22 GPa for the Cu_1.8S-1%Ru bulk composite was higher than that of other state-of-art TE materials. Compositing with ruthenium might be an approach worth promoting to synergistically improve the thermoelectric and mechanical performance of other materials.