Mechanochemical synthesis of high thermoelectric performance bulk Cu2X (X = S, Se) materials

We devised a single-step mechanochemical synthesis/densification procedure for Cu2X (X = S, Se) thermoelectric materials via applying a pressure of 3 GPa to a stoichiometric admixture of elemental Cu and X for 3 min at room temperature. The obtained bulk materials were single-phase, nearly stoichiometric structures with a relative packing density of 97% or higher. The structures contained high concentration of atomic scale defects and pores of 20-200 nm diameter. The above attributes gave rise to a high thermoelectric performance: at 873 K, the ZT value of Cu2S reached 1.07, about 2.1 times the value typical of samples grown from the melt. The ZT value of Cu2Se samples reached in excess of 1.2, close to the state-of-the-art value.