Article Dans Une Revue Journal of Physical Chemistry C Année : 2024

Influence of Disorder in High-Entropy Alloys on Thermoelectric Properties and Phase Stability

Résumé

High-entropy alloys (HEA) are characterized by a multielement composition and extensive atomic mixing. To explore the impact of disorder in PbSnTeSe HEA on its thermoelectric (TE) properties and phase stability, we have built two structurally ordered alloys with the same composition as that of the disordered one. Ordered alloys have been designed by artificially setting the positions of the atoms so that they form a symmetrical structure rather than a completely random structure. The symmetrical alloys have a tetragonal structure and an orthorhombic one. It is found that all the structures are mechanically stable while only the HEA is dynamically stable. The multi-cell Monte Carlo algorithm (MC)2 predicts a single phase of the HEA, which is consistent with the literature experimental results. The analysis of free energy shows that the HEA has the lowest values. These results suggest that HEA is more stable than the two symmetrical structures, emphasizing the role of atomic disorder in the stability of high-entropy alloys. Utilizing first-principles density functional theory (DFT) and Boltzmann transport theory, the thermoelectric transport properties of these symmetrical structures have been analyzed and compared to those of the disordered structure. The results indicate small optimal-value differences in the Seebeck coefficient S. The optimal values of S are approximately 180 μV/K, except for the n-type ORTH, for which S is only 100 μV/K. The electrical conductivity of ORTH and TET increases compared to that of HEA. For a temperature of 300 K and a carrier concentration of 1021 cm–3, the n-type conductivity increases from 75 × 105 S/m for HEA to 110 × 105 S/m and 120 × 105 S/m for ORTH and TET; the p-type conductivity increases from 5.5 × 105 S/m for HEA to 16 × 105 S/m and 17 × 105 S/m for ORTH and TET. The lattice thermal conductivities determined by the Green–Kubo formalism are similar for both the HEA and the two ordered structures. This suggests that the low thermal conductivity in high-entropy alloys primarily stems from multielement composition, with atomic disorder playing a minor role. Based on the electronic and thermal transport coefficients, the figure-of-merit ZT values have been determined. Compared to HEA, the optimal ZT value of the n-type ORTH and TET decreases, but for the p-type doping, the ZT value increases from 0.75 for HEA to 1.1 for both TET and ORTH.

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Dates et versions

hal-04915699 , version 1 (27-01-2025)

Identifiants

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Ming Xia, Marie-Christine Record, Pascal Boulet. Influence of Disorder in High-Entropy Alloys on Thermoelectric Properties and Phase Stability. Journal of Physical Chemistry C, 2024, 128 (29), pp.12010-12022. ⟨10.1021/acs.jpcc.4c02309⟩. ⟨hal-04915699⟩
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