High thermoelectric performance realized in porous Cu1.8S based composites by Na2S addition

Abstract

Digenite (Cu1.8S), one of superionic conductors, possesses the exceptional electrical transports performance but unsatisfactory thermal transport properties, which desiderates to be improved to become the candidate for use in the field of thermoelectric application. The porous Cu1.8S based composites with Na2S polycrystalline bulk samples were prepared via the incorporation of mechanical alloying (MA) and spark plasma sintering (SPS) technique by employing Na2S·9H2O as a addictive. The hydrate assists to create a porous structure and to refine grains during the fabrication procedure. Benefiting from the strengthened phonons scattering by additional multiscale pores after introducing Na2S, the thermal conductivity was dramatically decreased which results in an overall increased thermoelectric efficiency. The optimal thermoelectric figure of merit (ZT) of 0.78 at 773 K is obtained for Cu1.8S+2 wt % Na2S sample, which is 60% higher than that (0.49) of pristine Cu1.8S.