Abstract

In this thesis, we have conducted a study of the structural, electronic, mechanical, and thermoelectric properties of the layered compounds CdSbS3 and CdSbSe3, which are two new members of the MAX3 family. To achieve our objective, we used an ab initio calculation approach based on density functional theory (DFT), taking into account an empirical van der Waals (vdW) correction. In this work, we used the Vienna Ab-initio Simulation Package (VASP). And the semi-classical Boltzmann transport theory to calculate the thermoelectric properties.
In the first step, the structural, electronic, and mechanical properties of the compounds were studied. The results obtained show that these compounds are narrow bandgap semiconductors. The analysis of the electronic structure indicates that the character of the valence band maximum mainly comes from the p states of the S and Se atoms. In addition, they exhibit mechanical, dynamic, and thermodynamic stability. The results show that their interlayer distances are wider than those of most transition metal dichalcogenide compounds. Furthermore, regarding the average mobilities, they are reasonably high for electrons and holes, but a considerable anisotropy is observed. In the in-plane directions, the electron mobility is higher than the out-of-plane mobility (z direction) in both compounds.
In a second step, this work focuses on the thermoelectric properties. We discuss in detail the effect of temperature on these properties. We report that the lattice thermal conductivity κl, at room temperature, is 0.53 Wm-1K-1 for CdSbS3 and 0.13 Wm-1K-1 for CdSbSe3. The latter value is similar to that of ZnPSe3, which has been found to be lower than all other 2D materials. More remarkably, the thermoelectric figure of merit of CdSbS3 reaches 2.34 at 1400 K and 2.68 for CdSbSe3 at 850 K, which is a very high record at this temperature. Moreover, their thermoelectric figure of merit exceeds unity above room temperature.

Keywords: CdSbS3, CdSbSe3, MAX3, DFT, van der Waals, electronic properties, mechanical properties, thermoelectric properties, lattice thermal conductivity, figure of merit.

Information

Item Type:	Thesis
Divisions:	» Laboratory of Physics for Matter and Radiation » Faculty of Science and Technology
ePrint ID:	5412
Date Deposited:	2025-06-03
Further Information:	Google Scholar
URI:	https://www.univ-soukahras.dz/en/publication/article/5412

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