Structural and Thermoelectric Properties of Solid–Liquid In 4 Se 3 -In Composite

The aim of our work was to investigate thermoelectric properties of a composite of solid In 4 Se 3 and solid or liquid indium. Polycrystalline In 4 Se 3 -In composites were prepared by a direct reaction of elements, powdering of products and sintering powders by pulsed electric current sintering technique. Microstructural and structural properties of obtained composites were analyzed using SEM + EDX and XRD techniques. Electrical transport properties and thermal conductivity were measured over a temperature range of 323 K ≤ T ≤ 673 K. Results show that the electrical conductivity of composite increases about four times in comparison with that of pristine In 4 Se 3 . The thermal conductivity decreases in a systematic way with the increase of In content and reaches a value of about 0.44 W m −1 K −1 . As a result, the addition of indium enhances the thermoelectric figure of merit ZT from 0.8 to 1.2 at 673 K. However, we found that the melting of indium at about 430 K has no significant influence on thermoelectric properties of composites. We assume that the improvement of electrical properties is mainly due to the formation of point defects in In 4 Se 3 phase and metallic properties of the In phase. To analyze formation energies of possible defects in In 4 Se 3 structure, DFT calculations within the molecular cluster model were carried out. It was found that the In interstitial atoms are energetically more favorable than the formation of Se vacancy in In 4 Se 3 structure.