Study of thermoelectric properties of InGaN/GaN superlattice

2011 ◽  
Vol 1329 ◽  
Author(s):  
Hung-Hsun Huang ◽  
Yuh-Renn Wu
Keyword(s):  
Thermal Conductivity ◽  
Electrical Properties ◽  
Figure Of Merit ◽  
Phonon Dispersion ◽  
Boltzmann Transport ◽  
Superlattice Structure ◽  
Operation Temperature ◽  
Relaxation Time Approximation ◽  
Thermal And Electrical Properties ◽  
Callaway Model

ABSTRACTAs many reports show that the superlattice structure could greatly enhance the figure of merit ZT value for the thermoelectric application. We studied the thermal and electrical properties of the InGaN/GaN superlattice structure, and further analyze the thermoelectric features with different superlattice period, doping concentration, and operation temperature. The elastic continuum model and Callaway model have been applied to calculate the phonon dispersion relation and the thermal conductivity, respectively. The electrical properties are obtained by the Boltzmann transport equation with the relaxation time approximation. Simulation results indicate that both the reduced thermal conductivity and enhanced power factor would have the contribution to the enhancement of the figure of merit ZT.

scholarly journals Highly Anisotropic Thermal Transport in LiCoO2

2019 ◽  
Author(s):  
Hui Yang ◽  
Jia-Yue Yang ◽  
Christopher Savory ◽  
Jonathan Skelton ◽  
Benjamin Morgan ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Lithium Ion Batteries ◽  
Phonon Dispersion ◽  
Lithium Ion ◽  
Boltzmann Transport ◽  
Heat Management ◽  
Positive Electrodes ◽  
Anharmonic Lattice ◽  
Anharmonic Interactions ◽  
The Impact

<div>LiCoO<sub>2</sub> is the prototype cathode in lithium ion batteries. It adopts a crystal structure with alternating Li<sup>+</sup> and CoO<sub>2</sub><sup>-</sup> layers along the hexagonal <0001> axis. It is well established that ionic and electronic conduction is highly anisotropic; however, little is known regarding heat transport. We analyse the phonon dispersion and lifetimes of LiCoO<sub>2</sub> using anharmonic lattice dynamics based on quantum chemical force constants. Around room temperature, the thermal conductivity in the hexagonal ab plane of the layered cathode is ≈ 6 times higher than that along the c axis based on the phonon Boltzmann transport. The low thermal conductivity (< 10Wm<sup>-1</sup>K<sup>-1</sup>) originates from a combination of short phonon lifetimes associated with anharmonic interactions between the octahedral face-sharing CoO<sub>2</sub><sup>-</sup> networks, as well as grain boundary scattering. The impact on heat management and thermal processes in lithium ion batteries based on layered positive electrodes is discussed.</div>

Thermal Diffusivity and Conductivity of La0.7Ca0.3-xSrxMnO3 (x=0 to 0.10)

2012 ◽  
Vol 501 ◽  
pp. 319-323
Author(s):  
Hasan A. Alwi ◽  
Lay S. Ewe ◽  
Zahari Ibrahim ◽  
Noor B. Ibrahim ◽  
Roslan Abd-Shukor
Keyword(s):  
Thermal Conductivity ◽  
Electrical Conductivity ◽  
Grain Size ◽  
Transition Temperature ◽  
Thermal Diffusivity ◽  
Electrical Properties ◽  
Room Temperature ◽  
Electronic Contribution ◽  
Insulator Metal Transition ◽  
Thermal And Electrical Properties

We report the room temperature thermal conductivity κ and thermal diffusivity α of polycrystalline La0.7Ca0.3-xSrxMnO3 for x = 0 to 0.1. The samples were prepared by heating at 1220 and 1320oC. The insulator-metal transition temperature, TIM and thermal diffusivity increased with Sr content. Phonon was the dominant contributor to thermal conductivity and the electronic contribution was less than 1%. Enhancement of electrical conductivity σ and thermal diffusivity for x ≥ 0.08 was observed in both series of samples. The grain size of the samples (28 to 46 µm) does not show any affect on the thermal and electrical properties.

Increasing Efficiencies of Thermoelectric Devices Through Angular Interface Geometries

2009 ◽  
Author(s):  
D. P. Sellan ◽  
C. H. Amon
Keyword(s):  
Thermal Conductivity ◽  
Figure Of Merit ◽  
Equation Model ◽  
Boltzmann Transport ◽  
Thermoelectric Efficiency ◽  
Thermoelectric Figure ◽  
Subsequent Increase ◽  
Acoustic Mismatch ◽  
Out Of Plane ◽  
Plane Direction

The phonon Boltzmann transport equation model is used to evaluate the reduction of out-of-plane thermal conductivity and subsequent increase in thermoelectric figure of merit when an angular interface is patterned between a germanium thin-film and silicon substrate. According to the acoustic mismatch model, the angular structure reduces the out-of-plane thermal conductivity by spatially redistributing phonons traveling in the out-of-plane direction. Simulation results demonstrate a 43% reduction in out-of-plane thermal conductivity when operating in the fully ballistic regime. This decrease in phononic thermal conductivity would result in an increase of intrinsic thermoelectric efficiency by a factor of 1.75.

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.

Thermal Annealing Effect on the Thermal and Electrical Properties of Organic Semiconductor Thin Films

MRS Advances ◽  
2016 ◽  
Vol 1 (22) ◽  
pp. 1637-1643 ◽  
Author(s):  
Xinyu Wang ◽  
Boyu Peng ◽  
Paddy Chan
Keyword(s):  
Thermal Conductivity ◽  
Electrical Properties ◽  
Thermal Annealing ◽  
Organic Semiconductor ◽  
Field Effect ◽  
Annealing Temperature ◽  
Waste Heat ◽  
Annealing Effect ◽  
Field Effect Mobility ◽  
Thermal And Electrical Properties

ABSTRACTThe thermal and electrical properties of organic semiconductor are playing critical roles in the device applications especially on the devices with large area. Although the effect may be minor in a single device like field effect transistors, the unwanted waste heat would cause much more severe problems in large-scale devices as the power density will go up significantly. The waste heat would lead to performance degradation or even failure of the devices, and thus a more detailed study on the thermal conductivity and carrier mobility of the organic thin film would be beneficial to predict the limits of the device or design a thermally stable device. Here we explore the thermal annealing effect on the thermal and electrical properties of the small molecule organic semiconductor, dinaphtho[2,3-b:2’,3’-f]thieno[3,2-b]thiophene (DNTT). After the post deposition thermal annealing, the grain size of the film increases and in-plane crystallinity improves while cross-plane crystallinity keeps relatively constant. We demonstrated the cross-plane thermal conductivity is independent of the thermal annealing temperature and high annealing temperature will reduce the space-charge-limited current (SCLC) mobility. When the annealing temperature increase from 24 °C to 140 °C, the field effect mobility shows a gradual increase while the threshold voltage shifts from positive to negative. The different dependence of the SCLC mobility and field effect mobility on the annealing temperature suggest the improvement of the film crystallinity after thermal annealing is not the only dominating effect. Our investigation provides the constructive information to tune the thermal and electrical properties of organic semiconductors.

Expanded Chlorinated Rubber

1937 ◽  
Vol 10 (4) ◽  
pp. 798-800
Author(s):  
P. Schidrowitz ◽  
C. A. Redfarn
Keyword(s):  
Thermal Conductivity ◽  
Thermal Properties ◽  
Electrical Properties ◽  
Electric Heating ◽  
Research Association ◽  
British Patent ◽  
Rubber Material ◽  
Insulating Material ◽  
Thermal And Electrical Properties ◽  
Aluminum Plates

Abstract In a previous publication (J. Soc. Chem. Ind., 54, 263T–267T (1935); Rubber Chem. and Tech., 8, 613 (1935)) some particulars were given regarding the production and development of a hard spongy material from chlorinated rubber (British Patent No. 424,561). Thermal and Electrical Properties Some preliminary tests on the thermal and electrical properties of the material have now been carried out, and these serve to confirm the view that expanded chlorinated rubber should prove to be a very good insulating material. Thermal Conductivity.—The details given herewith are taken from a report by the Research Association of British Rubber Manufacturers. The thermal conductivity was determined by comparison with cork, a good insulating material of which the thermal properties are fairly well known. The method used consisted in placing slabs of cellular rubber and of cork each between a pair of aluminum plates, and then interposing between the two sets of plates an electric heating plate made of wire enclosed between sheets of mica. The plates, heater, and sheets of expanded chlorinated rubber material and cork were all of the same size, namely, 20.3 by 10.25 cm. The aluminum plates were 0.625 cm. thick.

scholarly journals Highly Anisotropic Thermal Transport in LiCoO2

2019 ◽  
Author(s):  
Hui Yang ◽  
Jia-Yue Yang ◽  
Christopher Savory ◽  
Jonathan Skelton ◽  
Benjamin Morgan ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Lithium Ion Batteries ◽  
Phonon Dispersion ◽  
Lithium Ion ◽  
Boltzmann Transport ◽  
Heat Management ◽  
Positive Electrodes ◽  
Anharmonic Lattice ◽  
Anharmonic Interactions ◽  
The Impact

<div>LiCoO<sub>2</sub> is the prototype cathode in lithium ion batteries. It adopts a crystal structure with alternating Li<sup>+</sup> and CoO<sub>2</sub><sup>-</sup> layers along the hexagonal <0001> axis. It is well established that ionic and electronic conduction is highly anisotropic; however, little is known regarding heat transport. We analyse the phonon dispersion and lifetimes of LiCoO<sub>2</sub> using anharmonic lattice dynamics based on quantum chemical force constants. Around room temperature, the thermal conductivity in the hexagonal ab plane of the layered cathode is ≈ 6 times higher than that along the c axis based on the phonon Boltzmann transport. The low thermal conductivity (< 10Wm<sup>-1</sup>K<sup>-1</sup>) originates from a combination of short phonon lifetimes associated with anharmonic interactions between the octahedral face-sharing CoO<sub>2</sub><sup>-</sup> networks, as well as grain boundary scattering. The impact on heat management and thermal processes in lithium ion batteries based on layered positive electrodes is discussed.</div>

Synthesis and Thermoelectric Properties of WO3/Cu2SnSe3 Composites

2018 ◽  
Vol 913 ◽  
pp. 811-817 ◽  
Author(s):  
Di Wu ◽  
Ji Ai Ning ◽  
De Gang Zhao ◽  
Xue Zhen Wang ◽  
Na Liu
Keyword(s):  
Thermal Conductivity ◽  
Electrical Conductivity ◽  
Electrical Properties ◽  
Grain Boundary ◽  
Figure Of Merit ◽  
Milling Process ◽  
Thermoelectric Figure Of Merit ◽  
Thermoelectric Figure ◽  
Plasma Sintering ◽  
Spark Plasma

In this study, nanometer WO3 powder was uniformly dispersed into the Cu2SnSe3 powder by ball milling process, and the WO3/Cu2SnSe3 thermoelectric composite was prepared by spark plasma sintering (SPS). The results showed that the nano-WO3 particles were mainly distributed in the grain boundary of Cu2SnSe3 matrix, and the grain growth of Cu2SnSe3 was inhibited. The addition of nano-WO3 could enhance the electrical conductivity of Cu2SnSe3, and while the Seebeck coefficient increased slightly for the 0.4% WO3/Cu2SnSe3 composite. The thermal conductivity was not decreased until the content of WO3 exceeded 1.6%. The highest thermoelectric figure of merit ZT of 0.177 was achieved at 700 K for 0.4% WO3/Cu2SnSe3 composite. The enhancement of ZT value of WO3/Cu2SnSe3 thermoelectric material was mainly attributed to the improvement of the electrical properties.

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