Large-scale colloidal synthesis of Cu5FeS4 compounds and their application in thermoelectrics

We report a large-scale colloidal synthesis (CS) of non-stoichiometric Cu5FeS4 powders at different temperatures (493 K, 533 K and 553 K) followed by spark plasma sintering. It is found that the carrier density of the CS samples is four orders of magnitude higher than those of samples synthesized by traditional solid state reaction methods (SS). The higher carrier density in CS non-stoichiometric Cu5FeS4 yields enhanced electrical conductivities and power factors over a wide temperature range. As a result, a zT value of 0.56 is achieved in the Cu5FeS4 compound synthesized through the colloidal synthesis process at 533 K, which is about 47% higher than that of their bulk SS counterparts. Moreover, these CS samples show a better mechanical performance compared to the SS samples, demonstrating the great potential of bornite based compounds for commercial thermoelectric applications.