Thermal Conductivity of One-Dimensional Silicon-Germanium Alloy Nanowires

2009 ◽  
Author(s):  
Yunki Gwak ◽  
Vinay Narayanunni ◽  
Sang-Won Jee ◽  
Anastassios A. Mavrokefalos ◽  
Michael T. Pettes ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Energy Conversion ◽  
Silicon Germanium ◽  
Figure Of Merit ◽  
Mean Free Path ◽  
Thermoelectric Efficiency ◽  
One Dimensional ◽  
Thermoelectric Energy ◽  
Germanium Alloy ◽  
Alloy Nanowires

Thermal properties of one dimensional nanostructures are of interest for thermoelectric energy conversion. Thermoelectric efficiency is related to non dimensional thermoelectric figure of merit, ZT = (S^2 σT)/k where S, σ, k are the Seebeck coefficient, electrical conductivity and thermal conductivity respectively. These physical properties are interdependent, and hence making ZT of a material high is very challenging work. However, when the size of nanostructure is comparable to the wavelength and mean free path of energy carriers, it is feasible to avoid such interdependence to enhance ZT energy conversion. [1–3]

Thermoelectric Transport in Silicon Germanium Nanocomposite

2008 ◽  
Author(s):  
Hohyun Lee ◽  
Daryoosh Vashaee ◽  
Xiaowei Wang ◽  
Giri Joshi ◽  
Gaohua Zhu ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Energy Conversion ◽  
Silicon Germanium ◽  
Figure Of Merit ◽  
Waste Heat ◽  
Electrical Energy ◽  
Energy Conversion Efficiency ◽  
Thermoelectric Effects ◽  
Thermoelectric Transport ◽  
Potential Applications

Direct energy conversion between heat and electrical energy based on thermoelectric effects is attractive for potential applications in waste heat recovery and environmentally-friendly refrigeration. The energy conversion efficiency depends on the dimensionless figure of merit of thermoelectric materials, ZT, which is proportional to the electrical conductivity, the square of the Seebeck coefficient, and the inverse of the thermal conductivity. Currently, the low ZT values of available materials restrict the applications of this technology. However, significant enhancements in ZT were recently reported in nanostructured materials such as superlattices mainly due to their low thermal conductivities. According to recent studies, the reduced thermal conductivity of nanostructures is attributed to the large number of interfaces at which phonons are scattered. Based on this idea, nanocomposites are expected to have a lower thermal conductivity than their bulk counterparts with low fabrication cost just by mixing nano sized particles. In this work, we will discuss mechanisms of thermoelectric transport via modeling and provide experimental evidence on the enhancement of thermoelectric figure of merit in SiGe-based nanocomposites.

Fundamental insight into control of thermal conductivity in silicon-germanium alloy nanowires

2014 ◽  
Vol 1707 ◽  
Author(s):  
Yongjin Lee ◽  
Gyeong S. Hwang
Keyword(s):  
Thermal Conductivity ◽  
Silicon Germanium ◽  
Nonequilibrium Molecular Dynamics ◽  
Boundary Scattering ◽  
Alloy Scattering ◽  
Scattering Effect ◽  
Germanium Alloy ◽  
Alloy Nanowires ◽  
Fundamental Insight ◽  
Insight Into

ABSTRACTWe present a computational analysis of thermal transport in Silicon-Germanium alloy nanowires (SiGeNWs), particularly focusing on the relative roles of alloy scattering and boundary scattering to the significant reduction of thermal conductivity (κ). Our nonequilibrium molecular dynamics (NEMD) simulations confirm the strong dependence of κ on Si:Ge ratio, as observed in previous experimental studies. Interestingly, as the amount of impurity increases, the difference in κ between SiGe bulk and SiGeNW becomes smaller. Especially, κSiGeNW and κSiGe have similar κ values when the Ge content is 20-80 %. From a nonequilibrium Green’s function (NEGF)-density functional theory (DFT) analysis, it is suggested that the most reduction in transmission channels is attributed to the strong alloy scattering effect for both Si0.8Ge0.2 bulk and Si0.8Ge0.2 NW. The boundary scattering effect in the SiGe alloy system seems to be unimportant as alloy scattering is dominant. The improved understanding provides fundamental insight into how to modify Si-based materials to enhance their thermoelectric (TE) properties through nanostructuring and alloying.

Effect of High Temperature Annealing on the Thermoelectric Properties of GaP Doped SiGe

1987 ◽  
Vol 97 ◽  
Author(s):  
Jan W. Vandersande ◽  
Charles Wood ◽  
Susan Draper
Keyword(s):  
Thermal Conductivity ◽  
Electrical Resistivity ◽  
Power Factor ◽  
Silicon Germanium ◽  
Figure Of Merit ◽  
Annealing Temperature ◽  
High Temperature Annealing ◽  
Rich Phase ◽  
Temperature Range ◽  
Thermoelectric Energy

ABSTRACTSilicon-germanium alloys doped with GaP are used for thermoelectric energy conversion in the temperature range 300°C - 1000°C. The conversion efficiency depends on Z - S2/ρΛ, a material's parameter (the figure of merit), where S is the Seebeck coefficient, ρ is the electrical resistivity and Λ is the thermal conductivity. The annealing of several samples in the temperature range of 1100°C - 1300°C resulted in the power factor P (=S2/ρ) increasing with increased annealing temperature. This increase in P was due to a decrease in ρ which was not completely offset by a drop in S2 suggesting that other changes besides that in the carrier concentration took place. SEM and EDX analysis of the samples indicated the formation of a Ca- P-Ge rich phase as a result of the annealing. It is speculated that this phase is associated with the improved properties. Several reasons which could account for the improvement in the Power factor of annealed GaP doped SiGe are given.

Thermal Resistance of Silicon/Germanium Interfaces From Lattice Dynamics Calculations

2009 ◽  
Author(s):  
E. S. Landry ◽  
A. J. H. McGaughey
Keyword(s):  
Thermal Conductivity ◽  
Thermal Resistance ◽  
Energy Conversion ◽  
Silicon Germanium ◽  
Lattice Dynamics ◽  
Phonon Scattering ◽  
Semiconductor Interfaces ◽  
Thermoelectric Energy ◽  
Interface Scattering ◽  
Computer Chips

Phonon scattering at the interface between two materials results in a thermal resistance, R [1]. An ability to accurately predict the thermal resistance of semiconductor interfaces is important in devices where phonon interface scattering is a significant contributor to the overall thermal resistance (e.g., computer chips with high component density). This ability will also lead to improvements in the design of semiconductor superlattices with low thermal conductivity, desirable in thermoelectric energy conversion applications [2].

Improving the Thermoelectric Properties of the Material and Increasing the Efficiency of Conversion Processes

2021 ◽  
Vol 23 (5) ◽  
pp. 243-246
Author(s):  
D.G. Mustafaeva ◽  
Keyword(s):  
Thermal Conductivity ◽  
Electrical Conductivity ◽  
Thermoelectric Properties ◽  
Figure Of Merit ◽  
Mean Free Path ◽  
Charge Carriers ◽  
Thermoelectric Figure Of Merit ◽  
Thermoelectric Efficiency ◽  
Thermoelectric Figure ◽  
Phonon Component

The area of practical application of thermoelectric materials depends on the value of the thermoelectric figure of merit. The use of semiconductor materials makes it possible to realize the conditions under which the ratio of their parameters ensures the achievement of high values of thermoelectric figure of merit. The achievement of the maximum thermoelectric figure of merit causes an increase in the efficiency of conversion processes due to the improvement of the thermoelectric properties of the material. The position of the maximum value of the thermoelectric figure of merit is predetermined by the scattering parameters and the ratio of the mobilities and effective masses of charge carriers. The nature of the change in electrical conductivity is determined by the behavior of the concentration of charge carriers. Thermal conductivity, like electrical conductivity, is proportional to the concentration of electrons and the mean free path. An increase in thermoelectric efficiency is achieved by optimizing thermoelectric parameters by doping and improving the properties of com¬pounds, which leads to an optimization of the concentration of charge carriers, a change in the density of states, and a decrease in the phonon component of thermal conductivity. The improvement of the thermoelectric properties of the material and the increase in the efficiency of the conversion processes are provided at a certain concentration of charge carriers, which corresponds to the optimal value.

scholarly journals Thermoelectric Efficiency of Silicon–Germanium Alloys in Finite-Time Thermodynamics

Entropy ◽  
2020 ◽  
Vol 22 (10) ◽  
pp. 1116 ◽  
Author(s):  
Patrizia Rogolino ◽  
Vito Antonio Cimmelli
Keyword(s):  
Thermal Conductivity ◽  
Finite Time ◽  
Silicon Germanium ◽  
Finite Time Thermodynamics ◽  
Thermoelectric Efficiency ◽  
Thermoelectric Energy ◽  
Different Temperatures ◽  
Nonlinear Regression Method ◽  
Relationship Of ◽  
The Relationship

We analyze the efficiency in terms of a thermoelectric system of a one-dimensional Silicon–Germanium alloy. The dependency of thermal conductivity on the stoichiometry is pointed out, and the best fit of the experimental data is determined by a nonlinear regression method (NLRM). The thermoelectric efficiency of that system as function of the composition and of the effective temperature gradient is calculated as well. For three different temperatures (T=300 K, T=400 K, T=500 K), we determine the values of composition and thermal conductivity corresponding to the optimal thermoelectric energy conversion. The relationship of our approach with Finite-Time Thermodynamics is pointed out.

scholarly journals Anomalous thermal conductivity enhancement in low dimensional resonant nanostructures due to imperfections

Nanoscale ◽  
2021 ◽  
Author(s):  
Hongying Wang ◽  
Yajuan Cheng ◽  
Zheyong Fan ◽  
Yangyu Guo ◽  
Zhongwei Zhang ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Energy Conversion ◽  
Thermal Conductivity Enhancement ◽  
Heat Management ◽  
Thermoelectric Energy Conversion ◽  
Conductivity Enhancement ◽  
Thermoelectric Energy ◽  
Low Dimensional

Nanophononic metamaterials have broad applications in fields such as heat management, thermoelectric energy conversion, and nanoelectronics. Phonon resonance in pillared low-dimensional structures has been suggested to be a feasible approach...

scholarly journals High thermoelectric performance enabled by convergence of nested conduction bands in Pb7Bi4Se13 with low thermal conductivity

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Lei Hu ◽  
Yue-Wen Fang ◽  
Feiyu Qin ◽  
Xun Cao ◽  
Xiaoxu Zhao ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Waste Heat ◽  
Low Frequency ◽  
Thermoelectric Performance ◽  
Environmental Crisis ◽  
Quality Factors ◽  
Thermoelectric Efficiency ◽  
Low Thermal Conductivity ◽  
Conduction Bands ◽  
Thermoelectric Energy

AbstractThermoelectrics enable waste heat recovery, holding promises in relieving energy and environmental crisis. Lillianite materials have been long-term ignored due to low thermoelectric efficiency. Herein we report the discovery of superior thermoelectric performance in Pb7Bi4Se13 based lillianites, with a peak figure of merit, zT of 1.35 at 800 K and a high average zT of 0.92 (450–800 K). A unique quality factor is established to predict and evaluate thermoelectric performances. It considers both band nonparabolicity and band gaps, commonly negligible in conventional quality factors. Such appealing performance is attributed to the convergence of effectively nested conduction bands, providing a high number of valley degeneracy, and a low thermal conductivity, stemming from large lattice anharmonicity, low-frequency localized Einstein modes and the coexistence of high-density moiré fringes and nanoscale defects. This work rekindles the vision that Pb7Bi4Se13 based lillianites are promising candidates for highly efficient thermoelectric energy conversion.

scholarly journals Термоэлектрические свойства нанокомпозитного Bi-=SUB=-0.45-=/SUB=-Sb-=SUB=-1.55-=/SUB=-Te-=SUB=-2.985-=/SUB=- с микрочастицами SiO-=SUB=-2-=/SUB=-

2019 ◽  
Vol 53 (6) ◽  
pp. 751
Author(s):  
А.А. Шабалдин ◽  
П.П. Константинов ◽  
Д.А. Курдюков ◽  
Л.Н. Лукьянова ◽  
А.Ю. Самунин ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Solid Solution ◽  
Electrical Conductivity ◽  
Wide Temperature Range ◽  
Figure Of Merit ◽  
Nanostructured Material ◽  
Thermoelectric Figure Of Merit ◽  
Thermoelectric Efficiency ◽  
Thermoelectric Figure ◽  
P Type

AbstractNanocomposite thermoelectrics based on Bi_0.45Sb_1.55Te_2.985 solid solution of p -type conductivity are fabricated by the hot pressing of nanopowders of this solid solution with the addition of SiO_2 microparticles. Investigations of the thermoelectric properties show that the thermoelectric power of the nanocomposites increases in a wide temperature range of 80–420 K, while the thermal conductivity considerably decreases at 80–320 K, which, despite a decrease in the electrical conductivity, leads to an increase in the thermoelectric efficiency in the nanostructured material without the SiO_2 addition by almost 50% (at 300 K). When adding SiO_2, the efficiency decreases. The initial thermoelectric fabricated without nanostructuring, in which the maximal thermoelectric figure of merit ZT = 1 at 390 K, is most efficient at temperatures above 350 K.

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