Combined effects of indium nanoinclusion and Se-deficiency on thermoelectric performance of n-type indium selenide

Abstract

In 4Se3, a member of the lead free chalcogenide family, is a promising thermoelectric material with layered structure. In this work, we explored the structural and thermoelectric transport properties of In4Se3 and In4Se3-x (0.25 ≤ x ≤ 0.55) with an aim to investigate the presence of Se-vacancy in In4Se3-x material system and its effect in the thermoelectric properties. A collective process of solid state reaction, ball milling and spark plasma sintering was used to prepare the compounds. Se-vacancy along with the presence of indium nanoparticles of 20–50 nm with the main orthorhombic In4Se3 phase was established. The Se-vacancy in In4Se3-x enhanced the power factor by increasing the carrier concentration. A significant reduction in the lattice thermal conductivity in In4Se3-x enhanced the thermoelectric figure of merit with maximum ZT of 1.03 achieved at 699 K for In4Se2.6 among the series of samples. It is found that the position of the Fermi level as a result of the carrier concentration together with a smaller band gap is responsible for a significant increase in power factor.