High thermoelectric and mechanical performance in highly dense Cu2−xS bulks prepared by a melt-solidification techniqueElectronic supplementary information (ESI) available: Temperature dependence of power factor (PF) for the fabricated Cu2S and Cu1.97S bulks (Fig. S1); temperature dependence of the specific heat for the fabricated Cu2S and Cu1.97S (Fig. S2); differential scanning calorimeter thermal response plots for the fabricated Cu1.97S bulks (Fig. S3); ideal version of unit cell and primiti

Highly dense Cu 2− x S bulks, fabricated by a melt-solidification technique, show high thermoelectric performance with zT of ∼1.9 at 970 K. The Cu 2− x S bulks show good thermal heat flow and diffusivity stability, and they exhibit excellent mechanical properties, with hardness of ∼1 GPa. Density functional theory calculations indicate that Cu 2− x S is an intrinsic p-type conductor. Highly dense Cu 2− x S bulks, fabricated by a melt-solidification technique, show high thermoelectric performance with zT of ∼1.9 at 970 K.