scholarly journals Lattice Thermal Conductivity of mGeTe•nSb2Te3 Phase-Change Materials: A First-Principles Study

Crystals ◽  
2019 ◽  
Vol 9 (3) ◽  
pp. 136 ◽  
Author(s):  
Yuanchun Pan ◽  
Zhen Li ◽  
Zhonglu Guo
Keyword(s):  
Thermal Conductivity ◽  
Phase Change ◽  
Data Storage ◽  
First Principles ◽  
Phase Change Materials ◽  
Lattice Thermal Conductivity ◽  
Transport Theory ◽  
Large Contribution ◽  
Thermal Transport Property ◽  
Boltzmann Transport Theory

As the most promising materials for phase-change data storage, the pseudobinary mGeTe•nSb2Te3 (GST) chalcogenides have been widely investigated. Nevertheless, an in-depth understanding of the thermal-transport property of GST is still lacking, which is important to achieve overall good performance of the memory devices. Herein, by using first-principles calculations and Boltzmann transport theory, we have systematically studied the lattice thermal conductivity along the out of plane direction of both stable hexagonal and meta-stable rock-salt-like phases of GST, and good agreement with available experiments has been observed. It is revealed that with the increase of the n/m ratio, the lattice thermal conductivity of hexagonal GST increases due to the large contribution from the weak Te-Te bonding, while an inverse trend is observed in meta-stable GST, which is due to the increased number of vacancies that results in the decrease of the lattice thermal conductivity. The size effect on thermal conductivity is also discussed. Our results provide useful information to manipulate the thermal property of GST phase-change materials.

scholarly journals Effects of low dimensionality on electronic structure and thermoelectric properties of bismuth

RSC Advances ◽  
2019 ◽  
Vol 9 (69) ◽  
pp. 40670-40680 ◽  
Author(s):  
C. Y. Wu ◽  
L. Sun ◽  
J. C. Han ◽  
H. R. Gong
Keyword(s):  
Thermal Conductivity ◽  
Electronic Structure ◽  
Band Structure ◽  
First Principles ◽  
Lattice Thermal Conductivity ◽  
Transport Theory ◽  
First Principles Calculations ◽  
Boltzmann Transport ◽  
Boltzmann Transport Theory ◽  
Low Dimensionality

First-principles calculations and Boltzmann transport theory have been combined to comparatively investigate the band structure, phonon spectrum, lattice thermal conductivity, and the transport properties of the β-bismuth monolayer and bulk Bi.

Ultralow lattice thermal conductivity at room temperature in 2D KCuSe from first-principles calculations

2021 ◽  
Author(s):  
Zhiyuan Xu ◽  
Cong Wang ◽  
Xuming Wu ◽  
Lei Hu ◽  
Yuqi Liu ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
First Principles ◽  
Figure Of Merit ◽  
Room Temperature ◽  
Lattice Thermal Conductivity ◽  
Transport Theory ◽  
First Principles Calculations ◽  
Boltzmann Transport ◽  
Thermoelectric Figure ◽  
Boltzmann Transport Theory

Ultralow lattice thermal conductivity is crucial to achieve a high thermoelectric figure of merit for thermoelectric applications. In this work, using the first-principles and phonon Boltzmann transport theory, we investigate...

scholarly journals Realizing and Adjusting the Thermoelectric Application of MoO3 Monolayer via Oxygen Vacancies

2019 ◽  
Author(s):  
Wenwen Zheng ◽  
Wei Cao ◽  
Ziyu Wang ◽  
Huixiong Deng ◽  
Jing Shi ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Thermoelectric Properties ◽  
First Principles ◽  
Oxygen Vacancies ◽  
Transport Theory ◽  
Electronic Conductivity ◽  
Boltzmann Transport ◽  
Anisotropic Behavior ◽  
Boltzmann Transport Theory ◽  
Thermoelectric Application

We have investigated the thermoelectric properties of MoO3 monolayer and its defective structures with oxygen vacancies by using first-principles method combined with Boltzmann transport theory. Our results show that the thermoelectric properties of MoO3 monolayer exhibit an anisotropic behavior which is caused by the similar anisotropic phenomenon of electronic conductivity and thermal conductivity. Moreover, the creation of oxygen vacancies proves to be an effective way to enhance the ZT values of MoO3 monolayer which is caused by the sharp peak near the Fermi level in density of states. The increased ZT value can reach 0.84 along x-axis at 300K.

scholarly journals Improvement of the thermoelectric properties of a MoO3 monolayer through oxygen vacancies

2019 ◽  
Vol 10 ◽  
pp. 2031-2038
Author(s):  
Wenwen Zheng ◽  
Wei Cao ◽  
Ziyu Wang ◽  
Huixiong Deng ◽  
Jing Shi ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Thermoelectric Properties ◽  
Density Of States ◽  
First Principles ◽  
Figure Of Merit ◽  
Oxygen Vacancies ◽  
Transport Theory ◽  
Boltzmann Transport ◽  
Anisotropic Behavior ◽  
Boltzmann Transport Theory

We have investigated the thermoelectric properties of a pristine MoO3 monolayer and its defective structures with different oxygen vacancies using first-principles methods combined with Boltzmann transport theory. Our results show that the thermoelectric properties of the MoO3 monolayer exhibit an evident anisotropic behavior which is caused by the similar anisotropy of the electrical and thermal conductivity. The thermoelectric materials figure of merit (ZT) value along the x- and the y-axis is 0.72 and 0.08 at 300 K, respectively. Moreover, the creation of oxygen vacancies leads to a sharp peak near the Fermi level in the density of states. This proves to be an effective way to enhance the ZT values of the MoO3 monolayer. The increased ZT values can reach 0.84 (x-axis) and 0.12 (y-axis) at 300 K.

Thermoelectric performance of XI2 (X = Ge, Sn, Pb) bilayers

2021 ◽  
Author(s):  
Nan Lu ◽  
Jie Guan
Keyword(s):  
Thermal Conductivity ◽  
Figure Of Merit ◽  
Density Functional ◽  
Lattice Thermal Conductivity ◽  
Transport Theory ◽  
Boltzmann Transport ◽  
Functional Theory ◽  
Boltzmann Transport Theory ◽  
Dimensionless Figure Of Merit ◽  
Structure Calculations

Abstract We study the thermal and electronic transport properties as well as the TE performance of three two-dimensional XI2 (X = Ge, Sn, Pb) bilayers using density functional theory and Boltzmann transport theory. We compared the lattice thermal conductivity, electrical conductivity, Seebeck coefficient, and dimensionless figure of merit (ZT) for the XI2 monolayers and bilayers. Our results show that the lattice thermal conductivity at room temperature for the bilayers is as low as ~1.1-1.7 Wm-1K-1, which is about 1.6 times as large as the monolayers for all the three materials. Electronic structure calculations show that all the XI2 bilayers are indirect-gap semiconductors with the band gap values between 1.84 eV and 1.96 eV at PBE level, which is similar as the corresponding monolayers. The calculated results of ZT show that the bilayer structures display much less direction dependent TE efficiency and have much larger n-type ZT values compared with the monolayers. The dramatic difference between the monolayer and bilayer indicates that the inter-layer interaction plays an important role in the TE performance of XI2, which provides the tunability on their TE characteristics.

scholarly journals Phonon Transport and Thermoelectric Properties of Imidazole-Graphyne

Materials ◽  
2021 ◽  
Vol 14 (19) ◽  
pp. 5604
Author(s):  
Yanyan Chen ◽  
Jie Sun ◽  
Wei Kang ◽  
Qian Wang
Keyword(s):  
Thermal Conductivity ◽  
Lattice Thermal Conductivity ◽  
Transport Theory ◽  
Hole Concentration ◽  
Chemical Properties ◽  
Phonon Transport ◽  
Thermoelectric Performance ◽  
Boltzmann Transport ◽  
Boltzmann Transport Theory ◽  
Carbon Based

The pentagon has been proven to be an important structural unit for carbon materials, leading to different physical and chemical properties from those of hexagon-based allotropes. Following the development from graphene to penta-graphene, a breakthrough has very recently been made for graphyne—for example, imidazole-graphyne (ID-GY) was formed by assembling experimentally synthesized pentagonal imidazole molecules and acetylenic linkers. In this work, we study the thermal properties and thermoelectric performance of ID-GY by combining first principle calculations with the Boltzmann transport theory. The calculated lattice thermal conductivity of ID-GY is 10.76 W/mK at 300 K, which is only one tenth of that of γ-graphyne (106.24 W/mK). A detailed analysis of the harmonic and anharmonic properties, including the phonon group velocity, phonon lifetime, atomic displacement parameter, and bond energy curves, reveals that the low lattice thermal conductivity can be attributed to the low Young’s modulus, low Debye temperature, and high Grüneisen parameter. Furthermore, at room temperature, ID-GY can reach a high ZT value of 0.46 with a 5.8 × 1012 cm−2 hole concentration, which is much higher than the value for many other carbon-based materials. This work demonstrates that changing structural units from hexagonal to pentagonal can significantly reduce the lattice thermal conductivity and enhance the thermoelectric performance of carbon-based materials.

Thermal Conductivity Measurements and Modeling of Phase-Change GST Materials

2007 ◽  
Author(s):  
Yizhang Yang ◽  
Taehee Jeong ◽  
Hendrik F. Hamann ◽  
Jimmy Zhu ◽  
Mehdi Asheghi
Keyword(s):  
Thermal Conductivity ◽  
Phase Change ◽  
Data Storage ◽  
Flash Memory ◽  
Performance Optimization ◽  
Phase Change Materials ◽  
Memory Cell ◽  
Data Access ◽  
Optical Recording ◽  
Access Time

Phase-change technology has been widely used in rewritable disks for optical recording applications. Recently, it has also received attention as a candidate for future high storage density non-volatile random access memory, due to its much longer cycle life (∼1013) and fast data access time (∼100ns) compared with the existing Flash memory technology. In this paper, we present thermal conductivity data and models for phase-change GeSbTe material that would be helpful in performance optimization and improvement in the reliability (i.e., enhancement of data rate, cyclability, control of mark-edge jitter) of phase-change-based data storage devices and systems. We perform the thermal characterization of Ge4Sb1Te5 and Ge2Sb2Te5 phase-change materials for the application of optical recording and phase-change memory cell using the techniques of thermoreflectance and electrical resistance thermometry. The limits of lattice and electronic thermal conductivities are investigated to determine their relative contributions as a function of tellurium concentration at different crystalline structures.

scholarly journals Promising Thermoelectric Performance in Two-Dimensional Semiconducting Boron Monolayer

2021 ◽  
Vol 9 ◽  
Author(s):  
Yonglan Hu ◽  
Ding Li ◽  
Rongkun Liu ◽  
Shichang Li ◽  
Chunbao Feng ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Lattice Thermal Conductivity ◽  
Transport Theory ◽  
Thermoelectric Performance ◽  
Two Dimensional ◽  
Boltzmann Transport ◽  
Hole Effective Mass ◽  
Boltzmann Transport Theory ◽  
Special Character ◽  
Type Power

A heavy element is a special character for high thermoelectric performance since it generally guarantees a low lattice thermal conductivity. Here, we unexpectedly found a promising thermoelectric performance in a two-dimensional semiconducting monolayer consisting of a light boron element. Using first-principles combined with the Boltzmann transport theory, we have shown that in contrast to graphene or black phosphorus, the boron monolayer has a low lattice thermal conductivity arising from its complex crystal of hexagonal vacancies. The conduction band with an intrinsic camelback shape leads to the high DOS and a high n-type Seebeck coefficient, while the highly degenerate valence band along with the small hole effective mass contributes to the high p-type power factor. As a result, we obtained the p-type thermoelectric figure of merit up to 0.96 at 300 K, indicating that the boron monolayer is a promising p-type thermoelectric material.

scholarly journals Excellent Room-Temperature Thermoelectricity of 2D GeP3: Mexican-Hat-Shaped Band Dispersion and Ultralow Lattice Thermal Conductivity

Molecules ◽  
2021 ◽  
Vol 26 (21) ◽  
pp. 6376
Author(s):  
Cong Wang ◽  
Zhiyuan Xu ◽  
Ke Xu ◽  
Guoying Gao
Keyword(s):  
Thermal Conductivity ◽  
Power Factor ◽  
Room Temperature ◽  
Lattice Thermal Conductivity ◽  
Transport Theory ◽  
Phonon Scattering ◽  
Quantum Confinement Effect ◽  
Boltzmann Transport Theory ◽  
Mexican Hat ◽  
P Type

Although some atomically thin 2D semiconductors have been found to possess good thermoelectric performance due to the quantum confinement effect, most of their behaviors occur at a higher temperature. Searching for promising thermoelectric materials at room temperature is meaningful and challenging. Inspired by the finding of moderate band gap and high carrier mobility in monolayer GeP3, we investigated the thermoelectric properties by using semi-classical Boltzmann transport theory and first-principles calculations. The results show that the room-temperature lattice thermal conductivity of monolayer GeP3 is only 0.43 Wm−1K−1 because of the low group velocity and the strong anharmonic phonon scattering resulting from the disordered phonon vibrations with out-of-plane and in-plane directions. Simultaneously, the Mexican-hat-shaped dispersion and the orbital degeneracy of the valence bands result in a large p-type power factor. Combining this superior power factor with the ultralow lattice thermal conductivity, a high p-type thermoelectric figure of merit of 3.33 is achieved with a moderate carrier concentration at 300 K. The present work highlights the potential applications of 2D GeP3 as an excellent room-temperature thermoelectric material.

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