Investigating Power Factor of CaMnO3 Added Carbon Nanotubes

2016 ◽  
Vol 675-676 ◽  
pp. 171-174 ◽  
Author(s):  
Meena Rittiruam ◽  
Arthorn Vora-Ud ◽  
Tosawat Seetawan
Keyword(s):  
Carbon Nanotubes ◽  
Electrical Resistivity ◽  
Electronic Structure ◽  
Energy Level ◽  
Seebeck Coefficient ◽  
Power Factor ◽  
Energy Gap ◽  
Boltzmann Distribution ◽  
Density Of State ◽  
High Electrical Resistivity

CaMnO3 (CMO) thermoelectric material is large Seebeck coefficient but high electrical resistivity. To reduce electrical resistivity by adding carbon nanotubes (CNTs) in CMO material and may be decreased Seebeck coefficient. In this work, we simulated electronic structure of CMO and CNTs-added CMO by DV-Xα method to investigation of power factor and enhance the thermoelectric performance. The Seebeck coefficient and electrical resistivity were calculated by Maxwell-Boltzmann distribution and Mott’s law to investigate power factor. The DV-Xa calculated show the energy level and density of state (DOS) of CMO and CNTs-added CMO demonstrated that the energy gap reduces from 3.33 eV to 0.19 eV affect to enhance the power factor of CMO with Seebeck coefficient and electrical resistivity are decreases. The power factor of CNTs-added CMO was increased with increasing CNTs content.

Carbon nanotubes enhanced Seebeck coefficient and power factor of rutile TiO2

2015 ◽  
Vol 17 (12) ◽  
pp. 8120-8124 ◽  
Author(s):  
Yao-Cheng Lai ◽  
Hsin-Jung Tsai ◽  
Chia-I Hung ◽  
Hiroyuki Fujishiro ◽  
Tomoyuki Naito ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Electrical Conductivity ◽  
Seebeck Coefficient ◽  
Power Factor ◽  
Filling Fraction ◽  
Rutile Tio2

Ti–C substitution occurs when carbon nanotubes were thermally dispersed in rutile TiO2 and the electrical conductivity as well as Seebeck coefficient were simultaneously promoted at a low filling fraction of tubes.

Thermoelectric Module of P-Type Ca-Co-O/N-Type ZnO Thin Films

2012 ◽  
Vol 622-623 ◽  
pp. 726-733 ◽  
Author(s):  
Weerasak Somkhunthot ◽  
Nuwat Pimpabute ◽  
Tosawat Seetawan
Keyword(s):  
Thin Films ◽  
Electrical Resistivity ◽  
Seebeck Coefficient ◽  
Power Factor ◽  
Electrical Power ◽  
Thermoelectric Module ◽  
Preliminary Test ◽  
Internal Resistance ◽  
Open Circuit ◽  
P Type

Thin films thermoelectric module fabricated by pulsed-dc magnetron sputtering system using Ca3Co4O9(p-type) and ZnO (n-type) targets of 60 mm diameter and 2.5 mm thickness, which were made from powder precursor, and obtained by solid state reaction. Thin films of p-Ca-Co-O (Seebeck coefficient = 143.85 µV/K, electrical resistivity = 4.80 mΩm, power factor = 4.31 µW/m K2) and n-ZnO (Seebeck coefficient =229.24 µV/K, electrical resistivity = 5.93 mΩm, power factor = 8.86 µW/m K2) were used to make a thermoelectric module, which consist of four pairs of legs connected by copper electrodes (0.5 mm thickness, 3.0 mm width, and 3.0-8.0 mm length). Each leg is 3.0 mm width, 20.0 mm length, and 0.44 µm thickness on a glass substrate of 1.0 mm thickness in dimension 25.0x50.0 mm2. For preliminary test, a module was used to thermoelectric power generation. It was found that the open circuit voltage increased with increasing temperature difference from 3 mV at 5 K up to 20 mV at 78 K. The internal resistance of a module reached a value of 14.52 MΩ. This test indicated that a module can be generated the electrical power. Therefore, it can be used as an important platform for further thin films thermoelectric module research.

PREPARATION OF N-TYPE HIGHER MANGANESE SILICIDE FILMS BY MAGNETRON SPUTTERING

2009 ◽  
Vol 23 (16) ◽  
pp. 3331-3348 ◽  
Author(s):  
Q. R. HOU ◽  
W. ZHAO ◽  
Y. B. CHEN ◽  
Y. J. HE
Keyword(s):  
Electrical Resistivity ◽  
Magnetron Sputtering ◽  
Seebeck Coefficient ◽  
Power Factor ◽  
Intermediate Layer ◽  
Activation Energies ◽  
Carbon Doping ◽  
Higher Manganese Silicide ◽  
Cap Layer ◽  
Manganese Silicide

N-type polycrystalline higher manganese silicide ( MnSi 1.7) films are prepared on thermally oxidized silicon substrates by magnetron sputtering. MnSi 1.85, Si , and carbon targets are used in the experiments. By co-sputtering of the MnSi 1.85 and Si targets, n-type MnSi 1.7 films are directly obtained. By increasing the Si content to the deposited films, both the Seebeck coefficient and electrical resistivity increase to high values. A Si intermediate layer between the MnSi 1.7 film and substrate plays an important role on the electrical properties of the films. Without the interlayer, the Seebeck coefficient is not stable and the electrical resistivity is higher. For preparation of MnSi 1.7 films by solid phase reaction, a sandwich structure Si / MnSi x/ Si (x < 1.7) and thermal annealing are used. A carbon cap layer is used as a doping source. With the carbon doping, the electrical resistivity of the MnSi 1.7 film decreases, while the Seebeck coefficient increases slightly. For reactive deposition, the MnSi x (x < 1.7) film is directly deposited on the heated substrate with a Si intermediate layer. By using a Si cap layer, a MnSi 1.7 film with a Seebeck coefficient of -292 μ V/K and electrical resistivity of 23 × 10-3 Ω- cm at room temperature is obtained. The power factor reaches 1636 μW/mK2 at 483 K. With such a high power factor, the n-type MnSi 1.7 material may be superior to p-type MnSi 1.7 material for the development of thermoelectric generators. Several smaller (0.036 - 0.099 eV ) and intermediate (0.10 - 0.28 eV ) activation energies are observed from the curves of logarithm of the resistivity versus reciprocal temperature. The larger activation energies (0.35 - 1.1 eV ) are consistent with the reported energy band gaps for higher manganese silicides.

Study Ratio Between the CuO and Eu2O3 Concentrations on Electrical Resistivity, Seebeck Coefficient and Power Factor of CuEu2O4

2021 ◽  
Vol 222 (1) ◽  
pp. 38-43
Author(s):  
P. Yamchumporn ◽  
K. Boonin ◽  
K. Singsoog ◽  
T. Seetawan ◽  
J. Kaewkho
Keyword(s):  
Electrical Resistivity ◽  
Seebeck Coefficient ◽  
Power Factor

Thermoelectric Properties of Carbon Nanotubes Added n-type CoSb3 Compound

2011 ◽  
Vol 1314 ◽  
Author(s):  
Takashi Itoh ◽  
Masashi Tachikawa
Keyword(s):  
Thermal Conductivity ◽  
Carbon Nanotubes ◽  
Electrical Resistivity ◽  
Seebeck Coefficient ◽  
Thermoelectric Properties ◽  
Phonon Scattering ◽  
Pulse Discharge ◽  
Molar Ratios ◽  
Performance Reduction ◽  
Compound Matrix

ABSTRACTCobalt triantimonide compounds are well known as materials with good thermoelectric properties over temperature range of 550-900 K. For further improving thermoelectric performance, reduction of thermal conductivity is required. In this study, we attempted to disperse carbon nanotubes (CNTs) homogeneously into the n-type CoSb3 compound for lowering lattice thermal conductivity by the phonon scattering. Powders of Co, Ni, Sb and Te were blended with molar ratios of n-type Co0.92Ni0.08Sb2.96Te0.04 compound, and the compound was synthesized through a pulse discharge sintering (PDS) process. After coarsely grinding the synthesized compound, CNTs were mixed with the compound powder at different mass% (0, 0.01, 0.05 and 0.1 mass%). Then, the mixture was mechanically ground with a planetary ball milling equipment. The ground composite powder was compacted and sintered by PDS. Thermoelectric properties (Seebeck coefficient, electrical resistivity and thermal conductivity) of the sintered samples were measured. It was confirmed that the fibrous CNTs existed homogeneously in the compound matrix. The absolute value of Seebeck coefficient slightly decreased with increase of CNT content. The minimum thermal conductivity was obtained at addition of 0.01mass%CNT, and the electrical resistivity was a little increased with CNT content. The maximum ZT of 0.98 was achieved at 853 K in the 0.01mass%CNT-added sample.

PHONON-DRAG EFFECT OF ULTRA-THIN FeSi2 AND MnSi1.7/FeSi2 FILMS

2011 ◽  
Vol 25 (22) ◽  
pp. 1829-1838 ◽  
Author(s):  
Q. R. HOU ◽  
B. F. GU ◽  
Y. B. CHEN ◽  
Y. J. HE
Keyword(s):  
Electrical Resistivity ◽  
Seebeck Coefficient ◽  
Single Crystals ◽  
Thermoelectric Power ◽  
Power Factor ◽  
Low Temperatures ◽  
Room Temperature ◽  
Phonon Drag ◽  
Drag Effect ◽  
Thermoelectric Power Factor

Phonon-drag effect usually occurs in single crystals at very low temperatures (10–200 K). Strong phonon-drag effect is observed in ultra-thin β- FeSi 2 films at around room temperature. The Seebeck coefficient of a 23 nm-thick β- FeSi 2 film can reach -1.375 mV/K at 343 K. However, the thermoelectric power factor of the film is still small, only 0.42×10-3 W/m-K2, due to its large electrical resistivity. When a 27 nm-thick MnSi 1.7 film with low electrical resistivity is grown on it, the thermoelectric power factor of the MnSi 1.7 film can reach 1.5×10-3 W/m-K2 at around room temperature. This value is larger than that of bulk MnSi 1.7 material in the same temperature range.

ELECTRONIC STRUCTURE AND QUANTUM PHASE TRANSITION IN MULTI-WALL CARBON NANOTUBES

2007 ◽  
Vol 21 (25) ◽  
pp. 4377-4386 ◽  
Author(s):  
SHI-DONG LIANG
Keyword(s):  
Phase Transition ◽  
Carbon Nanotubes ◽  
Electronic Structure ◽  
Quantum Phase Transition ◽  
Essential Role ◽  
Energy Gap ◽  
Tight Binding ◽  
Quantum Phase ◽  
Multi Wall Carbon Nanotubes ◽  
Structure Characteristics

The electronic structure of the multi-wall carbon nanotubes (MWCN) is studied theoretically by the tight-binding approach. The interwall coupling between layers plays an essential role in the electronic structure. With an increase of the interwall coupling, the energy gap of the semiconducting MWCNs will decrease and eventually vanish, giving rise to the semiconductor–metal quantum phase transition. The metallic layer in the MWCN dominates the electronic structure characteristics near the Fermi level (gapless).

Enhanced thermoelectric performance of SWNT/organic small molecule (OSM) hybrid materials by tuning of the energy level of OSMs

2020 ◽  
Vol 8 (37) ◽  
pp. 12795-12799
Author(s):  
Tae-hoon Kim ◽  
Jae Gyu Jang ◽  
Jong-In Hong
Keyword(s):  
Energy Level ◽  
Seebeck Coefficient ◽  
Hybrid Materials ◽  
Small Molecule ◽  
Power Factor ◽  
Thermoelectric Performance

The SWNT/dmBT hybrid with a low barrier of 0.06 eV between SWNT and dmBT showed a maximum Seebeck coefficient of 78.5 μV K−1 and a power factor of 183.9 μW m−1 K−1, 1.5 and 4.6 times higher compared to the SWNT/dCNBT with a high barrier of 0.64 eV.

Thermoelectric Properties of the Pseudogap Fe2VAl System

2004 ◽  
Vol 449-452 ◽  
pp. 909-912 ◽  
Author(s):  
Yoichi Nishino
Keyword(s):  
Electrical Resistivity ◽  
Electronic Structure ◽  
Low Temperature ◽  
Seebeck Coefficient ◽  
Room Temperature ◽  
Sharp Decrease ◽  
Large Power ◽  
Large Enhancement ◽  
Level Shifts ◽  
Temperature Resistivity

While the Heusler-type Fe2VAl compound exhibits a semiconductor-like behavior in electrical resistivity, doping of quaternary elements causes a sharp decrease in the low-temperature resistivity ρ and a large enhancement in the Seebeck coefficient S. Substantial enhancement in S can be explained on the basis of the electronic structure where the Fermi level shifts slightly from the center of a pseudogap either up- or downward depending on doping. In particular, a slight substitution of Si for Al leads to a large power factor (P = S2/ρ) of 5.5×10-3W/m K2at around room temperature.

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