Effect of selenium deficiency on the thermoelectric properties of n-type In4Se3-x compounds

Thermoelectric properties of dense bulk polycrystalline In4Se3-x (x = 0, 0.25, 0.5, 0.65, and 0.8) compounds are investigated. A peak dimensionless thermoelectric figure of merit (ZT) of about 1 is achieved for x = 0.65 and 0.8. The peak ZT is about 50% higher than the previously reported highest value for polycrystalline In4Se3-x compounds. Our In4Se3-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 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 In4Se3-x samples.