Two-dimensional buckling structure induces the ultra-low thermal conductivity: a comparative study of the group GaX (X = N, P, As)

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Layered LaCuOX (X = S, Se, and Te) have great potential for highperformance photoelectric (PE) applications, while little is known about their mechanical and thermal properties. The lack of this information will hinder understanding their transport mechanisms and applications as high TE/PE energy conversion efficiency devices. This study investigates the electronic, mechanical, and thermal properties of LaCuOX compounds. The investigated tetragonal crystals are all found to be mechanically stable. Besides, the mechanical stability and stiffness of layered LaCuOX weaken from LaCuOS to LaCuOTe, while their shear strain resistances are comparable. All the materials show good ductility and have ionic− covalent bonding. Since the Debye temperature and sound velocity decrease from LaCuOS to LaCuOTe, the thermal conductivity increases following the same order. Due to large Gruneisen parameters caused by strong phonon anharmonicity, ultralow thermal conductivities of LaCuOS, LaCuOSe, and LaCuOTe are found to be 2.58, 2.20, and 1.90 W/m K at 300 K, respectively. This work deepens the understanding of the physical properties of LaCuOX crystals, which may benefit in promoting their potential PE and thermoelectric applications.

Section: Resultssupporting

confidence: 87%

Section: Computational Detailsmentioning

confidence: 99%

Thermal Transport and Mechanical Properties of Layered Oxychalcogenides LaCuOX (X = S, Se, and Te)

Wang

Chen

Sun

et al. 2022

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“…Therefore, Al and I form the polarized covalent bond, which results in the stronger phonon anharmonicity, driving the low κ l of the monolayer Al 2 I 2 Se 2 . Similar phenomena are found in two-dimensional GaX (X = N, P, As) 52 and MSi 2 N 4 (M = Mo, W). 53 Additionally, large anisotropy ratios of κ ly /κ lx (>2) in the lattice thermal conductivity is found for the three monolayers, which originates from the anisotropic group velocities resulting from their layered lattice structures.…”

Section: Thermal Transport Mechanismssupporting

confidence: 78%

High Thermoelectric Performance of Al₂X₂Se₂ (X = Cl, Br, I) Monolayers with Strong Anisotropy in Lattice Thermal Conductivity

Sun

Chen

et al. 2022

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Recently, a class of thermoelectric (TE) materials with a FeOCl-type layered structure have been reported, such as GaOI, InOI, and TaCX (X = Cl, Br, I). These reports simulated further research on screening excellent TE monolayers with FeOCl-type structures. In this work, we carry out a comprehensive study on exploring the thermoelectric properties of Al2X2Se2 (X = Cl, Br, I) monolayers. The heat transport properties of the three monolayers are calculated and compared. Specifically, the thermal conductivities of 7.94 (16.98) W m–1 K–1 and 5.01 (16.15) W m–1 K–1 for the Al2Cl2Se2 and Al2Br2Se2 monolayers in the x direction (y direction) are obtained, respectively, which are more than that (0.29 (0.70) W m–1 K–1) for the Al2I2Se2 monolayer. The significant difference in the lattice thermal conductivity κl of Al2X2Se2 monolayers is attributed to their different phonon anharmonicity. It is also noted that strong anisotropy exists in the κl between the x and y directions. Additionally, the electronic transport parameters (the Seebeck coefficient and electrical conductivity) are figured out. Thus, the optimal ZT values of Al2X2Se2 monolayers from 200 to 700 K are obtained. It is found that the highest ZT value of the Al2I2Se2 monolayer (3.24) in the x direction is almost two times as higher as that (1.78) in the y direction at 700 K. The maximum ZT values of the Al2Cl2Se2 (0.59) and Al2Br2Se2 (0.95) monolayers in the y direction are higher than those of the Al2Cl2Se2 (0.34) and Al2Br2Se2 (0.77) monolayers in the x direction at 700 K, respectively, which are smaller than that of the Al2I2Se2 monolayer along with whether the x-axis (3.37) or the y-axis (1.75). This work reveals that the three monolayers exhibit anisotropies in the κl and ZT. The Al2I2Se2 monolayer has better TE performance than the Al2Cl2Se2 and Al2Br2Se2 monolayers.

“…The κ l of 2D materials has become a research hot spot in recent years since materials with high κ l will solve the heat dissipation problem of nanodevices. , In addition, a low κ l will overcome the traditional low efficiency of thermoelectric materials . Therefore, it is indispensable to study the TE properties of the novel two-dimensional material named Sc 2 I 2 S 2 to tap its potential value for application in heat transport, thermoelectricity, and the energy-related field.…”

Section: Resultsmentioning

confidence: 99%

“…55,56 In addition, a low κ l will overcome the traditional low efficiency of thermoelectric materials. 57 Therefore, it is indispensable to study the TE properties of the novel two-dimensional material named Sc 2 I 2 S 2 to tap its potential value for application in heat transport, thermoelectricity, and the energy-related field. We solved the phonon Boltzmann transport equation by DFT calculation and got the κ l result of Sc 2 I 2 S 2 .…”

Section: Stability Verificationmentioning

confidence: 99%

Monolayer Sc₂I₂S₂: An Excellent n-Type Thermoelectric Material with Significant Anisotropy

Yang

et al. 2022

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In recent years, FeOCl-type monolayers regarded as promising thermoelectrics (TE) have attracted a lot of attention. On the basis of first-principles calculations, this work reports excellent TE performance of two-dimensional (2D) Sc2I2S2 with strong anisotropy. At 700 K, 2D Sc2I2S2 exhibits anisotropic lattice thermal conductivities (κl) of 2.41 (x-direction) and 3.33 (y-direction) W/mK. In addition, high and anisotropic n-type PF values were also found in 2D Sc2I2S2, 20.9 (x-direction) and 0.65 (y-direction) mW m–1 K–2. The ZT value of 2.54 is found to be the largest in the x-direction based on n-type doping, which is 7 times higher than in the y-direction (0.35). The big difference in PF and κl reveals the origin of its anisotropy. Our results suggest that FeOCl-type monolayer Sc2I2S2 has excellent TE performance and exhibits strong anisotropy.