Thermoelectric Properties of Mixed Rhenium Chalcogenides Re6Te15-x Sex (0 ≤ × ≤ 8)

1998 ◽  
Vol 545 ◽  
Author(s):  
S. Kilibarda Dalafave ◽  
J. Ziegler ◽  
H. Mcallister
Keyword(s):  
Thermoelectric Power ◽  
Thermoelectric Properties ◽  
Power Factor ◽  
Room Temperature ◽  
Energy Gap ◽  
Selenium Concentration ◽  
X Ray ◽  
Tetragonal Lattice ◽  
Factor Α ◽  
Volume Decrease

AbstractReported are the temperature dependencies of the thermoelectric power and electrical resistivity of mixed rhenium chalcogenides Re6Te15-x,Sex (0 ≤ x ≤ 8) in the range 90–420 K. Influence of the partial chalcogen exchange on thermoelectric properties of these compounds is discussed. The samples are prepared by sintering elemental powders inside evacuated and sealed quartz ampoules at 1150 K for 170 hours. X-ray analysis reveals an orthorhombic lattice for samples with x < 8 and a tetragonal lattice for the Re6Te7Se8. sample. The lattice parameters and the unit cell volume decrease with increasing selenium concentration.The measurements indicate p-type semiconducting behavior for all samples. The presence of the energy gap is observed at higher temperatures (T ≥ 180–220 K) for all x. Data suggest hopping conduction at lower temperatures. Room temperature resistivities increase non-linearly from 6.9 to 20.4 Ω m with the increasing selenium content. Initially, the thermoelectric power a increases with temperature for all samples, with the fastest increase in Re6Se8 Te7 and the slowest in Re6Te15. The temperature at which a reaches maximum decreases with the increasing Se content. Above this temperature, a decreases uniformly as the temperature increases, the slowest increase being for Re6Se8Te7 and the fastest for Re6Te15. Such α(T) dependence is also discussed. The temperature dependence of the power factor, α2/ρ, is presented. Comparison of ρ, α, and the power factor in Re6SexTe15-x with currently used state-of-the-art materials is given.

Thermoelectric Properties of Doped Rhenium Chalcogenides Re6MxTe15 (x = 0, 1, 2; M = Ga, In, Ag)

1998 ◽  
Vol 545 ◽  
Author(s):  
S. Kilibarda Dalafave ◽  
H. Barcena ◽  
D. Henningsen
Keyword(s):  
Electrical Resistivity ◽  
Thermoelectric Power ◽  
Power Factor ◽  
Figure Of Merit ◽  
Energy Gap ◽  
Hopping Conduction ◽  
Theoretical Discussion ◽  
Local Maxima ◽  
Factor Α ◽  
Semiconducting Behavior

AbstractTemperature dependencies of the electrical resistivity, ρ, and the thermoelectric power, α, are reported for Re6 MxTe15 (M = Ga, In, Ag; x = 0, 1, 2) between 90–380 K. Theoretical discussion of the results is presented. The materials, synthesized by filling large voids in the Re6Te15 cluster system, may have potential thermoelectric applications around and below room temperatures. The samples are prepared by reacting 99.99% pure elemental powders in evacuated and sealed quartz ampoules at 1070 K for 170 hours. The resistivity data indicate semiconducting behavior for all samples. Possible hopping conduction is present at lower temperatures. The energy gap is observed at higher temperatures in all the samples.Positive values of α in Re6(Ga,In)x Te15 (x = 0, 1, 2) indicate p-type semiconducting behavior in the studied temperature range. For these samples α increases initially with temperature, then levels off to a nearly constant value. The positions of the sharp peaks in a, observed at lower temperatures for x = 1, 2 only, depend on the Ga (In) concentration. High values of a (∼ 300 μV/K) are measured at room temperatures. In Re6AgTe15 α has small positive values (∼ 20–40 μV/K) between 185 K and 270 K. Outside this range α is negative. It reaches local maxima of -340 μV/K at 105 K and -350 μV/K at 370 K. In Re6Ag2Te15 α changes from positive to negative values above 295 K. A maximum positive value of +350 μV/K is reached at 250 K and maximum negative of -250 μV/K at 330 K. The power factor, α2/ρ, increases with temperature for all studied samples. Theoretical fits to α(T) for all samples are discussed. Also discussed is the effect of filling the voids in the rhenium-telluride system on the figure of merit.

Synthesis and thermoelectric power factor of LSCO perovskites

2005 ◽  
Vol 886 ◽  
Author(s):  
Julio E. Rodriguez
Keyword(s):  
Electrical Resistivity ◽  
Seebeck Coefficient ◽  
Thermoelectric Power ◽  
Power Factor ◽  
Room Temperature ◽  
Morphological Properties ◽  
Measured Temperature ◽  
X Ray Diffraction ◽  
Thermoelectric Power Factor ◽  
X Ray

ABSTRACTMeasurements of Seebeck coefficient, S(T) and electrical resistivity, ρ(T) on polycrystalline La2−xSrxCuO4+d(LSCO) (0<x≤0.2) samples are reported. The Seebeck coefficient is positive in whole measured temperature range (77K and 300K) and it decreases with Sr content. At room temperature S(T) changes from 400 μ/K for the samples with the lowest levels of Sr to 30 μV/K for the samples with the highest Sr levels. The behavior of S(T) fits to Heikes model, which describes the behavior of Seebeck coefficient in systems where the correlated hopping is present. With the Sr content, the electrical resistivity changes its behavior from semiconducting to metallic and it took values from 2.4 to 10−3Ωcm. From S(T) and rho(T) measurements the thermoelectric power factor, PF was obtained. The maximum values for PF were about 5 μW/K2cm in the samples where x= 0.03, which are comparable to the typical values for conventional thermoelectric semiconductors. The structural and morphological properties of the samples were studied by x-ray diffraction analysis and Scanning Electron Microscopy (SEM) respectively. The behavior of transport properties opens de possibility of considering this family of perovskite-compounds as a thermoelectric material which works below room temperature.

scholarly journals Impact of the iron substitution on the thermoelectric properties of Co 1− x Fe x S 2 ( x  ≤ 0.30)

2019 ◽  
Vol 377 (2152) ◽  
pp. 20180337 ◽  
Author(s):  
Ulises Acevedo Salas ◽  
Ismail Fourati ◽  
Jean Juraszek ◽  
Fabienne Richomme ◽  
Denis Pelloquin ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Thermal Properties ◽  
Thermoelectric Properties ◽  
Thermoelectric Material ◽  
Power Factor ◽  
Room Temperature ◽  
Low Carbon ◽  
Energy Materials ◽  
Work Samples ◽  
Lattice Part

The strong interplay between magnetism and transport can tune the thermoelectric properties in chalcogenides and oxides. In the case of ferromagnetic CoS 2 pyrite, it was previously shown that the power factor is large at room temperature, reaching 1 mW m −1  K −2 and abruptly increases for temperatures below the Curie transition ( T C ), an increase potentially due to a magnonic effect on the Seebeck ( S ) coefficient. The too large thermal conductivity approximately equal to 10.5 W m −1  K −1 at room temperature prevents this pyrite from being a good thermoelectric material. In this work, samples belonging to the Co 1− x Fe x S 2 pyrite family ( x  = 0, 0.15 and 0.30) have thus been investigated in order to modify the thermal properties by the introduction of disorder on the Co site. We show here that the thermal conductivity can indeed be reduced by such a substitution, but that this substitution predominantly induces a reduction of the electronic part of the thermal conductivity and not of the lattice part. Interestingly, the magnonic contribution to S below T C disappears as x increases, while at high T , S tends to a very similar value (close to −42 µV K −1 ) for all the samples investigated. This article is part of a discussion meeting issue ‘Energy materials for a low carbon future’.

scholarly journals Annealing Effect on the Thermoelectric Properties of Bi2Te3Thin Films Prepared by Thermal Evaporation Method

2013 ◽  
Vol 2013 ◽  
pp. 1-6 ◽  
Author(s):  
Jyun-Min Lin ◽  
Ying-Chung Chen ◽  
Chi-Pi Lin
Keyword(s):  
Thin Films ◽  
Seebeck Coefficient ◽  
Thermoelectric Properties ◽  
Power Factor ◽  
Room Temperature ◽  
Annealing Temperature ◽  
Thermal Evaporation ◽  
Thermal Evaporation Method ◽  
Si Substrates ◽  
Seebeck Coefficients

Bismuth telluride-based compounds are known to be the best thermoelectric materials within room temperature region, which exhibit potential applications in cooler or power generation. In this paper, thermal evaporation processes were adopted to fabricate the n-type Bi2Te3thin films on SiO2/Si substrates. The influence of thermal annealing on the microstructures and thermoelectric properties of Bi2Te3thin films was investigated in temperature range 100–250°C. The crystalline structures and morphologies were characterized by X-ray diffraction and field emission scanning electron microscope analyses. The Seebeck coefficients, electrical conductivity, and power factor were measured at room temperature. The experimental results showed that both the Seebeck coefficient and power factor were enhanced as the annealing temperature increased. When the annealing temperature increased to 250°C for 30 min, the Seebeck coefficient and power factor of n-type Bi2Te3-based thin films were found to be about −132.02 μV/K and 6.05 μW/cm·K2, respectively.

Substitutional Effects on the Thermoelectric Properties of Transition Metal Pentatellurides

1998 ◽  
Vol 545 ◽  
Author(s):  
R. T. Littleton ◽  
J. W. Kolis ◽  
C. R. Feger ◽  
Terry M. Tritt
Keyword(s):  
Thermoelectric Properties ◽  
Room Temperature ◽  
Parent Compound ◽  
Substantial Reduction ◽  
Large Degree ◽  
Parent Materials ◽  
Se Doping ◽  
Low Dimensional ◽  
Ti Substitution ◽  
Factor Α

AbstractThe thermoelectric properties (resistivity and thermopower) of single crystals of the low-dimensional pentatelluride materials, Hffe5 and ZrTe5, have been measured as a function of temperature from 10K < T < 320K. Both parent materials exhibit a resistive transition peak, Tp ≈ 80K for HfTe5 and Tp ≈ 145K for ZrTe5. Each display a large positive (p-type) thermopower (α ≥ +125μV/K) around room temperature, which undergoes a change to a large negative (n-type) thermopower (α≤-125μV/K) below the peak temperature. The magnitude of this resistive anomaly is typically 3–7 times the room temperature value of ≈ 1 mΩ•cm. Through isoelectronic substitution of Zr for Hf (Hf1-xZrxTe5), a systematic shift is observed in Tp as the Zr concentration increases. Small Ti substitution for Hf and Zr affects the electronic properties strongly, producing a substantial reduction in Tp for either parent compound. However, the large values of thermopower and the magnitude of the resistive peak remain essentially unchanged. Substitutions of Se or Sb on the Te sites greatly affects the electronic behavior of the parent materials. Se doping increases the thermopower values by ≈20% while decreasing the resistivity by as much as 25%. These effects double the power factor, α2σT, of the parent materials. Small Sb substitutions appear to completely suppress the resistive anomaly. These features in the resistivity and thermopower signal a large degree of tunability in the temperature range of operation. The potential of these materials as candidates for low temperature thermoelectric applications will be discussed.

Optical energy gap variation in GaxIn1−x As alloys

1968 ◽  
Vol 46 (2) ◽  
pp. 157-159 ◽  
Author(s):  
John C. Woolley ◽  
Mathew B. Thomas ◽  
Alan G. Thompson
Keyword(s):  
Thermoelectric Power ◽  
Fermi Energy ◽  
Room Temperature ◽  
Energy Gap ◽  
Empirical Equations ◽  
Optical Energy Gap ◽  
Optical Energy ◽  
Good Agreement ◽  
Gap Values

Room-temperature optical energy-gap values have been determined for GaxIn1−x As alloys, and have been corrected, where necessary, for the Burstein effect by finding Fermi energy values from thermoelectric power data. The results show good agreement with the empirical equations given previously for mixed III–V alloys.

Improving the thermoelectric power factor of CNT/PEDOT:PSS nanocomposite films by ethylene glycol treatment

RSC Advances ◽  
2016 ◽  
Vol 6 (58) ◽  
pp. 53339-53344 ◽  
Author(s):  
Woohwa Lee ◽  
Young Hun Kang ◽  
Jun Young Lee ◽  
Kwang-Suk Jang ◽  
Song Yun Cho
Keyword(s):  
Ethylene Glycol ◽  
Thermoelectric Power ◽  
Thermoelectric Properties ◽  
Power Factor ◽  
Treatment Method ◽  
Nanocomposite Films ◽  
Thermoelectric Power Factor

This study investigates a treatment method with ethylene glycol for improving the thermoelectric properties of CNT/PEDOT:PSS nanocomposite films.

Thermoelectric Power Factor of Polycrystalline La0.75Sr0.25Co1-xMnxO3-δCeramics

2009 ◽  
Vol 1166 ◽  
Author(s):  
Julio E. Rodríguez ◽  
J. A. Niño
Keyword(s):  
Transport Properties ◽  
Thermoelectric Power ◽  
Power Factor ◽  
Figure Of Merit ◽  
Room Temperature ◽  
Manganese Content ◽  
Solid State Reaction Method ◽  
Measured Temperature ◽  
Thermoelectric Power Factor ◽  
Temperature Range

AbstractThermoelectric properties of polycrystalline La0.75Sr0.25Co1-xMnxO3-δ(0<x<0.08) (LSCoO-Mn) compounds have been studied. The samples were grown by solid-state reaction method; their transport properties were studied in the temperature range between 100 and 290K, as a function of temperature and the manganese content. The Seebeck coefficient (S) is positive over the measured temperature range and its magnitude increases with the manganese content up to values close to 160 μV/K. The electrical resistivity (ρ) goes from metallic to semiconducting behavior as the Mn level increases, at room temperature, ρ(T) exhibit values less than 4mΩ-cm. From S(T), ρ(T) and κ(T) data, the thermoelectric power factor and the figure of merit were determined. These performance parameters reach maximum values around 18 μW/K2-cm and 0.2, respectively. The observed behavior in the transport properties become these compounds potential thermoelectric materials, which could be used in thermoelectric applications.

Enhancement of thermoelectric power factor in CrSi2 film via Si:B addition

2015 ◽  
Vol 29 (27) ◽  
pp. 1550189
Author(s):  
Q. R. Hou ◽  
B. F. Gu ◽  
Y. B. Chen
Keyword(s):  
Electrical Resistivity ◽  
Thermoelectric Power ◽  
Raman Spectra ◽  
Power Factor ◽  
Low Temperatures ◽  
X Ray Diffraction ◽  
Thermoelectric Power Factor ◽  
X Ray ◽  
Large Enhancement ◽  
Diffraction Patterns

In this paper, we report a large enhancement in the thermoelectric power factor in CrSi2 film via Si:B (1 at.% B content) addition. The Si:B-enriched CrSi2 films are prepared by co-sputtering CrSi2 and heavily B-doped Si targets. Both X-ray diffraction patterns and Raman spectra confirm the formation of the crystalline phase CrSi2. Raman spectra also indicate the crystallization of the added Si:B. With the addition of Si:B, the electrical resistivity [Formula: see text] decreases especially at low temperatures while the Seebeck coefficient [Formula: see text] increases above 533 K. As a result, the thermoelectric power factor, [Formula: see text], is greatly enhanced and can reach [Formula: see text] at 583 K, which is much larger than that of the pure CrSi2 film.

scholarly journals The Effect of Thickness on the Physical Properties of Fe2O3 Thin Films Prepared by DC Magnetron Sputtering

2017 ◽  
Vol 28 (1) ◽  
pp. 149
Author(s):  
Baha'a A. Al-Hilli
Keyword(s):  
Film Thickness ◽  
Physical Properties ◽  
Room Temperature ◽  
Optical Constants ◽  
Energy Gap ◽  
Nano Particle ◽  
X Ray Diffraction ◽  
Thin Film Thickness ◽  
X Ray ◽  
Deposition Parameters

The objective of this study is to assess the influence of nano-particle Fe2O3 thin film thickness on some physical properties which were prepared by magnetron DC- sputtering on glass substrate at room temperature. The structure was tested with X-Ray diffraction and it was to be amorphous and to become single crystal with recognized peak in (003) after annealing at temperature 500oC. The physical properties as a function of deposition parameters and then film thickness were studied. The optical properties such as absorbance, energy gap and some optical constants are measured and found that of about (3eV) energy gap.

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