First‐Principles Study on Electronic and Thermal Transport Properties of FeRuTiX Quaternary Heusler Compounds (X=Si, Ge, Sn)

Abstract

The structural, electronic, thermal and lattice thermal transport properties of the three hypothetical quaternary Heusler alloys FeRuTiX (X=Si, Ge, Sn) were investigated with the aid of first‐principles calculations. All compounds were found to be semiconducting with a small indirect band gap. Flat bands near the conduction band edge and degenerate multi‐bands near the valance band edge suggest that these systems should exhibit both large Seebeck coefficients and good electrical conductivity. The analysis of the calculated vibrational spectra showed that the three compounds are thermodynamically stable. The computed lattice thermal conductivity indicates that among the three compounds that of FeRuTiSn is rather low at high temperature. Indeed, a low lattice thermal conductivity (∼3.5 Wm−1 K−1 at 1000 K) together with a small electronic band gap (0.51 eV) with an appropriate electronic structure (disperse and flat bands) render FeRuTiSn a promising candidate as a high‐temperature thermoelectric material.

Monolayer 1T-Ag6S2 with Excellent Thermoelectric Properties

“…66,67 Figure 10 illustrates the variation of κ l with temperature, and the κ l of 1T-Ag 6 S 2 along the x (y) axis is as low as 0.33 (0.27) W/mK at 300 K. This result is notably lower compared to the majority of 1T phase TMD materials and typical highperformance TE materials, such as 1T-ZrS 2 (the κ l is 2.39 W/ mK at 300 K), 1T-SnSe 2 (the κ l is 3.27 W/mK at 300 K), 1T-HfSe 2 (the κ l is 1.8 W/mK at 300 K), 56,68,69 Bi 2 Te 3 (the κ l is 1.5 W/mK at 300 K), Bi 2 TeSe 2 (the κ l is 0.81 W/mK at 300 substitution of Ag 6 clusters, which leads to a decrease in phonon group velocity and therefore significantly reduces its κ l . 30,54 As shown in Figure 3, since the substitution of Ag 6 reduces their overall frequency to 10 THz (the maximum phonon vibration frequency of most materials is much greater than 10 THz 71,72 ) and the frequency of the acoustic branch is also significantly reduced, as well as the degeneracy and phonon softening of the acoustic and optical branches in the lowfrequency region, 1T-Ag 6 S 2 will have lower phonon group velocity and greater anharmonics. Moreover, Hirata et al 73 incorporated Se elements to substitute S in Ag 2 S, yielding Ag 2 S 1−x Se x with remarkably low κ l values.…”

“…As shown in Figure , since the substitution of Ag 6 reduces their overall frequency to 10 THz (the maximum phonon vibration frequency of most materials is much greater than 10 THz , ) and the frequency of the acoustic branch is also significantly reduced, as well as the degeneracy and phonon softening of the acoustic and optical branches in the low-frequency region, 1T-Ag 6 S 2 will have lower phonon group velocity and greater anharmonics. Moreover, Hirata et al incorporated Se elements to substitute S in Ag 2 S, yielding Ag 2 S 1– x Se x with remarkably low κ l values.…”

First-principles screening of XSbF3 (X = Ba and Ra) fluoroperovskites: an insight into structural, optoelectronic and thermal properties

“…Furthermore, we have presented the energy versus volume (E-V) plots for both study compounds in figure 2. This optimization mechanism involved fitting the results to the Birch-Murnaghan equation of state (EOS) [64].…”