Microstructure and Thermoelectric Properties of B4C+TiB2 Composite by Hot Pressed Sintering

2014 ◽  
Vol 602-603 ◽  
pp. 910-915
Author(s):  
Zhen Ye Zhu ◽  
Xing Hong Zhang ◽  
Jie Cai Han
Keyword(s):  
Composite Material ◽  
Composite Materials ◽  
Thermoelectric Properties ◽  
Figure Of Merit ◽  
Milling Process ◽  
X Ray Diffraction ◽  
Thermoelectric Figure ◽  
Conductivity Increase ◽  
Thermal Conductivity Increase ◽  
Pressing Technology

TiB2 doped B4C composite whichTiB2 contents were 12.4% and 25.4% have been fabricated by the combination of the ball milling process and hot pressing technology. The phase analysis and microstructure of the composite materials are investigated through X-ray diffraction and scan electron microscope, respectively. In addition, thermoelectric properties of the composite materials are studied. The results show that the microcracks are easy to form in the interface between B4C and TiB2. It is also found that, the electrical and thermal conductivity increase wi2. Edit Paperth the increase of TiB2 doping, while the Seebeck coefficient decreases with the increase of TiB2 doping. The thermoelectric figure of merit of the B4C+25.4%TiB2 composite material is 50% higher than that of B4C at 573K, while the ZT of B4C+25.4% TiB2 composite material is lower than that of B4C at 873K.

Enhancement of thermoelectric figure of merit by incorporation of large single crystals in Ca3Co4O9 bulk materials

2003 ◽  
Vol 18 (7) ◽  
pp. 1646-1651 ◽  
Author(s):  
Ryoji Funahashi ◽  
Saori Urata ◽  
Toyohide Sano ◽  
Masaaki Kitawaki
Keyword(s):  
Electrical Conductivity ◽  
Composite Material ◽  
Single Crystals ◽  
Thermoelectric Properties ◽  
Figure Of Merit ◽  
Thermoelectric Figure Of Merit ◽  
Bulk Materials ◽  
Flux Method ◽  
Thermoelectric Figure ◽  
Grain Alignment

Having recently succeeded in synthesizing large single crystals of (Ca2CoO3)CoO2 (Co-349) with superior thermoelectric properties using a modified flux method, we have prepared a composite material of Co-349 powder and single crystals and examined its thermoelectric properties. The electrical conductivity σ of this composite, which contained 20 wt.% single crystals, was higher than that of a sample without the single crystals. While the achievable effect has yet to be fully realized, improved grain alignment and the effect of current bypassing grain boundaries through the large single crystals in the composite are thought to cause the increasing σ, which consequently results in an enhanced thermoelectric figure of merit of about 0.56 at 973 K in air.

scholarly journals Ba substitution for enhancement of the thermoelectric properties of LaCoO3 ceramics (0⩽x⩽0.75)

2019 ◽  
Vol 8 (4) ◽  
pp. 519-526 ◽  
Author(s):  
Mohamed Ali Bousnina ◽  
Fabien Giovannelli ◽  
Loïc Perriere ◽  
Guillaume Guegan ◽  
Fabian Delorme
Keyword(s):  
Thermoelectric Properties ◽  
Figure Of Merit ◽  
A Value ◽  
Best Value ◽  
Conductivity Increase ◽  
Thermal Conductivity Increase ◽  
Conventional Sintering ◽  
Increasing Temperature ◽  
P Type ◽  
Ba Substitution

AbstractIn the present work, dense perovskite ceramics were successfully prepared from a series of La1–xBaxCoO3 solid solutions in the range of substitution 0 ⩽ x ⩽ 0.75 using solid state reaction and conventional sintering. Structural properties of La1–xBaxCoO3 were systematically investigated and thermoelectric properties were measured in the temperature range of 330–1000 K. The results show that the thermoelectric properties of Ba-substituted LaCoO3 depend on x. Indeed, at 330 K, electrical conductivity presents an optimum value for x = 0.25 with a value of σmax ≈ 2.2×105 S·m−1 whereas the Seebeck coefficient decreases when x and/or the temperature increases. The Ba-substituted LaCoO3 samples exhibit p-type semiconducting behaviour. The best power factor value found is 3.4×10−4 W·m−1·K−2 at 330 K for x = 0.075, which is 10% higher than the optimum value measured in La1–xSrxCoO3 for x = 0.05. The thermal diffusivity and thermal conductivity increase with increasing temperature and Ba concentration. La1–xBaxCoO3 shows a maximum figure of merit (ZT = 0.048) for x = 0.05 at 330 K, 25% higher than the best value in La1−xSrxCoO3 compounds.

The Enhanced Thermoelectric Properties of Ba0.4Co4Sb11.7Te0.3 Prepared by the High-Pressure and High-Temperature Method

2014 ◽  
Vol 33 (1) ◽  
pp. 59-63
Author(s):  
Song Hao ◽  
Hong An Ma ◽  
Le Deng ◽  
Kai Kai Jie ◽  
Zhe Liu ◽  
...  
Keyword(s):  
High Pressure ◽  
High Temperature ◽  
Thermoelectric Properties ◽  
Figure Of Merit ◽  
Thermoelectric Figure Of Merit ◽  
X Ray Diffraction ◽  
Thermoelectric Figure ◽  
Seebeck Coefficients ◽  
Temperature Method ◽  
Increasing Temperature

AbstractPolycrystalline skutterudite Ba0.4Co4Sb11.7Te0.3 with a bcc crystal structure was prepared by the High-Pressure and High-Temperature (HPHT) method. The study explored a chemical method for introducing Ba atoms into the voids of CoSb3 to optimize the thermoelectric figure of merit ZT in the system of Ba0.4Co4Sb11.7Te0.3. The samples were characterized by X-ray diffraction, electron microprobe analysis, and thermoelectric properties measurement. The electrical resistivity, Seebeck coefficients and thermal conductivities of the samples were measured in the temperature range of 300–743 K. The power factor and the figure of merit, ZT, of the samples all increased with the increasing temperature. A dimensionless thermoelectric figure of merit of 0.87 at 743 K was achieved for n-type Ba0.4Co4Sb11.7Te0.3 at last. The results indicated Ba-filled CoSb3 prepared by HPHT method is an effective method to greatly enhance the thermoelectric properties of skutterudite compounds.

Effects of indium-filling and synthesis pressure on the thermoelectric properties of CoSb3

2014 ◽  
Vol 28 (15) ◽  
pp. 1450118 ◽  
Author(s):  
Le Deng ◽  
Li Bin Wang ◽  
Jie Ming Qin ◽  
Tao Zheng ◽  
Xiao Peng Jia ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Thermoelectric Properties ◽  
Figure Of Merit ◽  
Processing Time ◽  
Room Temperature ◽  
Thermoelectric Figure Of Merit ◽  
X Ray Diffraction ◽  
Thermoelectric Figure ◽  
X Ray ◽  
Scanning Electron

In x Co 4 Sb 12 skutterudite compounds have been prepared successfully at different synthesis pressures by high pressure and high temperature (HPHT) method, the processing time has been reduced from a few days to half an hour. In addition, the effect of synthesis pressure on the thermoelectric properties of In 0.4 Co 4 Sb 12 compounds has been investigated in this paper. The structure of In 0.4 Co 4 Sb 12 samples was evaluated by means of X-ray diffraction and scanning electron microscopy (SEM). The Seebeck coefficient, electrical resistivity and thermal conductivity were all measured in the temperature range of room temperature to 673 K. The sample synthesized at 2.0 GPa showed the highest power factor of 29.3 μWcm-1K-2 at 373 K. A dimensionless thermoelectric figure of merit (ZT) of 0.51 at 673 K was achieved for n-type In 0.4 Co 4 Sb 12 prepared at 1.3 GPa, which was significantly enhanced in comparison with pure CoSb 3.

Influence of multi-sintering on the thermoelectric properties of Bi2Sr2Co2Oy ceramics

2019 ◽  
Vol 34 (02) ◽  
pp. 2050019 ◽  
Author(s):  
Y. Zhang ◽  
M. M. Fan ◽  
C. C. Ruan ◽  
Y. W. Zhang ◽  
X.-J. Li ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Thermoelectric Properties ◽  
Figure Of Merit ◽  
Phonon Scattering ◽  
Sintered Sample ◽  
Thermoelectric Figure Of Merit ◽  
Thermoelectric Figure ◽  
The Third ◽  
Ceramic Samples ◽  
Optimum Formula

[Formula: see text] ceramic samples have a structure similar to phonon glass electronic crystals, and their thermoelectric properties can be effectively adjusted through repeated grinding and sintering. The results show that multi-sintering can make their grain refined and increase their grain boundary, which will effectively increase density and phonon scattering. Finally, multi-sintering can reduce the resistivity and thermal conductivity, thus obviously improve thermoelectric figure of merit [Formula: see text] of [Formula: see text]. The optimum [Formula: see text] value of 0.26 is achieved at 923 K by the third sintered sample.

Effects of Ce filling fraction and Fe content on the thermoelectric properties of Co-rich CeyFexCo4−xSb12

2001 ◽  
Vol 16 (3) ◽  
pp. 837-843 ◽  
Author(s):  
Xinfeng Tang ◽  
Lidong Chen ◽  
Takashi Goto ◽  
Toshio Hirai
Keyword(s):  
Thermal Conductivity ◽  
Thermoelectric Properties ◽  
Figure Of Merit ◽  
Single Phase ◽  
Lattice Thermal Conductivity ◽  
Hole Concentration ◽  
Thermoelectric Figure Of Merit ◽  
Thermoelectric Figure ◽  
Filling Fraction ◽  
Fe Content

Single-phase filled skutterudite compounds, CeyFexCo4−xSb12 (x = 0 to 3.0, y = 0 to 0.74), were synthesized by a melting method. The effects of Fe content and Ce filling fraction on the thermoelectric properties of CeyFexCo4−xSb12 were investigated. The lattice thermal conductivity of Ce-saturated CeyFexCo4−xSb12, y being at the maximum corresponding to x, decreased with increasing Fe content (x) and reached its minimum at about x = 1.5. When x was 1.5, lattice thermal conductivity decreased with increasing Ce filling fraction till y = 0.3 and then began to increase after reaching the minimum at y = 0.3. Hole concentration and electrical conductivity of Cey Fe1.5Co2.5Sb12 decreased with increasing Ce filling fraction. The Seebeck coefficient increased with increasing Ce filling fraction. The greatest dimensionless thermoelectric figure of merit T value of 1.1 was obtained at 750 K for the composition of Ce0.28Fe1.52Co2.48Sb12.

Stokes’ first problem for an electro-conducting micropolar fluid with thermoelectric properties

2010 ◽  
Vol 88 (1) ◽  
pp. 35-48 ◽  
Author(s):  
Magdy A. Ezzat ◽  
Hamdy M. Youssef
Keyword(s):  
Thermoelectric Properties ◽  
Micropolar Fluid ◽  
Inversion Formula ◽  
Figure Of Merit ◽  
Fourier Expansion ◽  
Fourier Transforms ◽  
Heat Sources ◽  
Layer Model ◽  
Thermoelectric Figure ◽  
Coupled Equations

This work is related to the flow of an electro-conducting micropolar fluid presenting thermoelectric properties effect in the presence of a magnetic field. The electro-conducting thermofluid equation of heat transfer with one relaxation time is derived. The flow of an electro-conducting micropolar fluid over a plate that is moved suddenly is considered. The governing coupled equations in the frame of the boundary-layer model are applied to Stokes' first problem with heat sources. Laplace-transform and Fourier-transform techniques are used to obtain the solution. The inverses of the Fourier transforms are obtained analytically. The Laplace transforms are obtained using the complex inversion formula of the transform together with Fourier-expansion techniques. Numerical results for the temperature distribution, the velocity, and the microrotation components are represented graphically. Thermoelectric figure-of-merit, Seebeck and Peltier effects on a micropolar fluid are studied.

Epitaxial Growth and Thermoelectric Properties of Bi2Te3 Based Low Dimensional Structures

2000 ◽  
Vol 626 ◽  
Author(s):  
Joachim Nurnus ◽  
Harald Beyer ◽  
Armin Lambrecht ◽  
Harald Böttner
Keyword(s):  
Thermoelectric Properties ◽  
Figure Of Merit ◽  
Lattice Mismatch ◽  
Structural Performance ◽  
Lead Chalcogenide ◽  
Thermoelectric Figure ◽  
Barrier Materials ◽  
Superlattice Structures ◽  
Low Dimensional ◽  
Secondary Ion

ABSTRACTBi2Te3 based low dimensional structures are interesting material systems to increase the thermoelectric figure of merit ZT by either the expected reduction of the thermal conductivity or by a possible power factor enhancement due to quantum confinement. Due to low lattice mismatch Bi2(Te1-xSex)3, PbSe1-xTex, as well as Pb1-xSrxTe, and BaF2 are suitable for Bi2Te3 based low dimensional structures. Especially due to their significantly enhanced band gap lead chalcogenide compounds like Pb1-xSrxTe (Pb0.87Sr0.13Te: 0.6 eV) are well-suited barrier materials in MQW structures. Alternatively the insulator BaF2 can be used for that purpose.Here we report mainly on results of different superlattice structures mentioned above grown by molecular beam epitaxy (MBE) on BaF2(111). The structural properties of these layers were investigated by X-ray diffractometry (XRD), scanning electron microscopy (SEM) and secondary ion mass spectroscopy (SIMS). Structural performance and thermoelectric properties of different Bi2Te3 based superlattices were reported and compared with regard to their superlattice parameters.

Influence of Encapsulation of Fullerenes on Optical and Thermoelectric Properties of Carbon Nanotubes

2021 ◽  
Vol 26 (2) ◽  
pp. 123-131
Author(s):  
E.V. Morozova ◽  
◽  
D.A. Timkaeva ◽  
Keyword(s):  
Thermal Conductivity ◽  
Carbon Nanotubes ◽  
Thermoelectric Properties ◽  
Figure Of Merit ◽  
C60 Fullerene ◽  
Zone Structure ◽  
Thermoelectric Figure ◽  
High Frequencies ◽  
The One ◽  
Coefficients Of Absorption

The hybrid systems based on the carbon nanotubes (CNT) and fullerenes (nanopipodes) are promising for applications in nanoelectronics. With insignificant variation of the CNT diameter the change of the fullerenes geometry takes place. The periodically located inside fullerenes represent a set of quantum points in the one-dimensional super-lattice. Using the variation of inside fullerenes it is possible to modulate the zone structure of the CNT – fullerene system and to control the electronic and phonon characteristics of nanopipodes. In the work the optical and thermoelectric properties of CNT with encapsulated molecules of C60 fullerene have been investigated. Using the first-principle methods the coefficients of absorption, optical conductivi-ty, thermal conductivity, thermoelectric figure of merit for CNT with fullerenes, periodically lo-cated inside the nanotubes at different distances from each other, have been calculated. It has been shown that with decreasing the distance between fullerenes the optical conductivity of CNT – C60 is suppressed at high frequencies. It has been determined that the conductance of the structures with fullerenes is less than the conductance of a clean tube, and approximately equal for considered distances (12.3 and 19.7 Å) between fullerenes. The CNT thermal conductivity due to the encapsulation of fullerenes considerably (3–4 times) decreases for the considered CNT (8.8) – C60 systems.

THERMAL CONDUCTIVITY AND THERMAL AGING PERFORMANCE OF Sn WITH 0.7 wt.% Cu and VARIOUS GRAPHENE ADDITIONS

2019 ◽  
Vol 27 (06) ◽  
pp. 1950161
Author(s):  
CAIXIA SUN ◽  
FENGYUN ZHANG ◽  
HONGXIA ZHANG ◽  
NIANLONG ZHANG ◽  
SHOUYING LI ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Composite Material ◽  
Composite Materials ◽  
Thermal Aging ◽  
X Ray Diffraction ◽  
Diffraction Intensity ◽  
A Value ◽  
Aging Test ◽  
Accelerated Thermal Aging ◽  
Aging Performance

The effect of graphene content (0.08, 0.16 and 0.33[Formula: see text]wt.%) on the thermal conductivity and thermal aging performance of an Sn based composite material with 0.7[Formula: see text]wt.% Cu and various graphene additions was investigated via X-ray diffraction (XRD), scanning electron microscope (SEM) and accelerated thermal aging test. The XRD results showed that the graphene diffraction intensity was weak (approximately 10∘) due to little content and distribution of the graphene on the surface of the composite materials. After thermal aging testing the diffraction intensity on some crystal planes of the composite materials was enhanced, proving that preferential growth occurs on the crystal plane. SEM results showed that before aging testing no whiskers were generated on the surface of the composite materials. After the accelerated thermal aging at 100∘C for 24[Formula: see text]h, whisker growth became apparent in the composite materials. All the whiskers were located in the grains rather than on the grain boundaries of the composite materials. The highest thermal conductivity was obtained at 0.16[Formula: see text]wt.% graphene addition (indicated as 0.16[Formula: see text]wt.% graphene–0.7[Formula: see text]wt.% Cu/Sn). After the accelerated thermal aging at 100∘C for 24[Formula: see text]h, the bamboo-shaped whiskers with a low aspect ratio grew in large quantities on the surface of the 0.16[Formula: see text]wt.% graphene–0.7[Formula: see text]wt.% Cu/Sn composite material, while when the aging was at 100∘C for 366[Formula: see text]h the thermal conductivity decreased from 67[Formula: see text]W[Formula: see text][Formula: see text][Formula: see text][Formula: see text] to 52[Formula: see text]W[Formula: see text][Formula: see text][Formula: see text][Formula: see text]. When the graphene addition was 0.33[Formula: see text]wt.% (indicated as 0.33[Formula: see text]wt.% graphene–0.7[Formula: see text]wt.% Cu/Sn) the thermal conductivity maintains a value above 59[Formula: see text]W[Formula: see text][Formula: see text][Formula: see text][Formula: see text] after the accelerated thermal aging.

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