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The Cu${}_{2-x}$Hg${}_x$Se (x = 0, 0.05, 0.10 and 0.15) nanopowders were fabricated using the hydrothermal synthesis, and then hot-pressed into bulk alloys. The effects of Hg doping on the thermoelectric (TE) properties of Cu₂Se were investigated. The electrical resistivities of all the doped samples are lower than that of the nondoped sample due to the induced cation vacancies. For the x = 0.10 and x = 0.15 samples, Seebeck coefficients increase slightly compared with the nondoped sample at higher temperature. Except for the sample of x = 0.05, the thermal conductivities of x = 0.10 and x = 0.15 samples are substantially lower than that of the x = 0.00 sample. As an overall result, the maximum value of ZT, which is the dimensionless TE figure of merit, reaches 1.50 at 600${}^{\circ }$C for the x = 0.10 sample.

The ${\mathrm{\text{Cu}}}_2\mathrm{\text{Se}}/x{\mathrm{\text{Ni}}}_{0.85}\mathrm{\text{Se}}$ ($x$ = 0, 0.025, 0.05, 0.075, 0.1, 0.15, 0.2, 0.3, 0.4 and 0.5) nanopowders were synthesized by the hydrothermal method and then were hot-pressed into bulk alloys. The effects of ${\mathrm{\text{Ni}}}_{0.85}\mathrm{\text{Se}}$ secondary phase on the thermoelectric (TE) properties of ${\mathrm{\text{Cu}}}_2\mathrm{\text{Se}}$ were investigated. For $x=0.025$ and $x=0.05$, both their electrical resistivity and Seebeck coefficients increase. While for $x\ge 0.075$, they decrease instead. The samples for $x\le 0.075$ have lower thermal conductivity. However, for $x\ge 0.1$, the thermal conductivity rises remarkably. As an overall result, the maximum value of dimensionless TE figure of merit (ZT) reaches 1.52 at 873 K for the sample of $x=0.05$, 36.5% higher than for the sample without ${\mathrm{\text{Ni}}}_{0.85}\mathrm{\text{Se}}$.