Thermoelectric properties of dense bulk polycrystalline ${\mathrm{In}}_4{\mathrm{Se}}_{3-x}$ ($x$ $=$ 0, 0.25, 0.5, 0.65, and 0.8) compounds are investigated. A peak dimensionless thermoelectric figure of merit ($\mathit{ZT}$) of about 1 is achieved for $x$ $=$ 0.65 and 0.8. The peak $\mathit{ZT}$ is about 50% higher than the previously reported highest value for polycrystalline ${\mathrm{In}}_4{\mathrm{Se}}_{3-x}$ compounds. Our ${\mathrm{In}}_4{\mathrm{Se}}_{3-x}$ samples were prepared by ball milling and hot pressing. We show that it is possible to effectively control the electrical conductivity and thermal conductivity by controlling selenium (Se) deficiency $x$. The $\mathit{ZT}$ enhancement is mainly attributed to the thermal conductivity reduction due to the increased phonon scattering by Se deficiency, defects, and nanoscale inclusions in the ball-milled and hot-pressed dense bulk ${\mathrm{In}}_4{\mathrm{Se}}_{3-x}$ samples.

• Received 22 November 2010

DOI:https://doi.org/10.1103/PhysRevB.83.115201