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1.
V. A. Kulbachinskii V. G. Kytin P. M. Tarasov N. A. Yuzeeva 《Physics of the Solid State》2010,52(9):1830-1835
The effect of Ga doping on the temperature dependences (5 K ≤ T ≤ 300 K) of the Seebeck coefficient α, electrical conductivity σ, thermal conductivity coefficient κ, and thermoelectric
figure of merit Z of p-(Bi0.5Sb0.5)2Te3 single crystals has been investigated. It has been shown that, upon Ga doping, the hole concentration decreases, the Seebeck
coefficient increases, the electrical conductivity decreases, and the thermoelectric figure of merit increases. The observed
variations in the Seebeck coefficient cannot be completely explained by the decrease in the hole concentration and indicate
a noticeable variation in the density of states due to the Ga doping. 相似文献
2.
V. A. Kulbachinski? V. G. Kytin P. M. Tarasov 《Journal of Experimental and Theoretical Physics》2010,110(4):618-621
The effect of gallium on the temperature dependences (5 K ≤ T ≤ 300 K) of Seebeck coefficient α, electrical conductivity σ, thermal conductivity k, and thermoelectric efficiency Z of mixed p-(Bi0.5Sb0.5)2Te3 semiconductor single crystals is studied. The hole concentration decreases upon gallium doping; that is, gallium causes a
donor effect. The Seebeck coefficient increases anomalously, i.e., much higher than it should be at the detected decrease
in the hole concentration. This leads to an enhancement of the thermoelectric power. The observed changes in the Seebeck coefficient
indicate a noticeable gallium-induced change in the density of states in the valence band. 相似文献
3.
Thin films of Sb-Te of varying compositions have been deposited on glass substrates following the three temperature method.
The dc conductivity (σ), Hall coefficient (R
H) and thermoelectric power (α) of annealed samples have been measured in the temperature range 300–470°K. Films exhibit metallic as well as semiconducting
characteristics withp-type conductivity. The properties are found to be dependent on composition and thickness of the film.
Paper presented at the Int. Conf. and Intensive Tutorial Course on Semiconductor Materials, New Delhi, India, December 8–16,
1988. 相似文献
4.
V S K Balagurusamy S Krishna Prasad S Chandrasekhar Sandeep Kumar M Manickam C V Yelamaggad 《Pramana》1999,53(1):3-11
We have studied the electrical conductivity of well aligned samples of hexahexylthiotriphenylene (HHTT) in the pure as well
as doped states. The dopant used was a small concentration (0.62 mole %) of the electron acceptor trinitrofluorenone (TNF).
In the columnar phases, doping causes the AC(1 kHz) conductivity along the columnar axis (σ
‖) to increase by a factor of 107 or more relative to that in undoped samples; σ
‖ attains a value of 10−2S/m, which was the maximum measurable limit of our experimental set up. On the other hand, in the isotropic phase doping makes
hardly any difference to the conductivity. The frequency dependence of the conductivity has been investigated. The DC conductivity
of doped samples exhibits an enormous anisotropy, σ
‖/σ
⊥ ≥ 1010, which is 7 orders higher than that reported for any liquid crystalline system, and, to our knowledge, the largest observed
in an organic conductor.
We also report the first thermoelectric power studies on these ‘molecular wires’. The sign of the thermoelectric power is
in conformity with the expected nature of the charge carriers, namely, holes. 相似文献
5.
T. S. Kamilov D. K. Kabilov I. S. Samiev Kh. Kh. Khusnutdinova 《Technical Physics》2005,50(10):1370-1373
The possibility of designing thermoelectric sensors based on multielement structures of higher manganese silicide (HMS) polycrystalline
films is considered. Test structures with various configurations are developed for studying electrical and thermoelectric
parameters of polycrystalline HMS films. The geometrical sizes of the elements of test structures are chosen to match the
grain size in polycrystalline HMS films. The test structures are prepared using the planar silicon technology. In these structures,
the current-voltage characteristics, Hall constant, charge carrier concentration, and mobility are measured. The thermopower
(α) and electrical conductivity (σ) are studied in a temperature range of T = 77–600 K, where α > 250 μV/K and electrical conductivity σ ∼ 20 (Ω cm)−1. It is shown that the sensitivity and thermopowers increase upon a decrease in the cross-sectional area of the elements. 相似文献
6.
L. N. Luk’yanova V. A. Kutasov P. P. Konstantinov V. V. Popov 《Physics of the Solid State》2010,52(8):1599-1605
The specific features of the variation in the thermoelectric figure-of merit Z for p-type bismuth- and antimony-chalcogenide-based solid solutions p-(Bi,Sb)2(Te,Se)3 have been analyzed with allowance made for the data amassed in the investigation of thermoelectric and galvanomagnetic properties.
It has been shown that, in the samples with optimum carrier concentrations, the increase in Z in the multicomponent p-Bi2 − x
Sb
x
Te3 − y
Se
y
composition (x = 1.3, y = 0.06) in the temperature range 300–370 K is mediated by the high carrier mobility and the low lattice thermal conductivity.
The higher effective mass of the density of states and the larger slope of the temperature dependence of the mobility as compared
to the other compositions bring about an increase in Z in the p-Bi2 − x
Sb
x
Te3 solid solution for x = 1.6 in the temperature range 370–550 K. The increase in the figure-of merit reached in the compositions under study stems
also from the increasing contraction of constant-energy ellipsoids along the binary and bisector directions and from the change
in the angle θ between the principal axes of the ellipsoids and the crystallographic axes. 相似文献
7.
Solid-polymer-blend electrolyte consisting of chitosan and polyethylene oxide (PEO) in a 1:1 weight ratio and doped with lithium
trifluoromethanesulfonimide (LiTFSI) salt was prepared by solution cast technique. The highest conducting film with conductivity
value of 1.40 × 10-6 S cm−1 at room temperature consists of 30 wt% LiTFSI. The temperature dependence for the highest conducting film obeyed Arrhenius
relationship. From loss tangent–frequency plots at different temperatures, the frequency f
max at which the plot is a maximum was obtained. From this, ln f
max vs 103/T was plotted. The activation energy value obtained from the log σ vs 103/T plot and ln f
max vs 103/T plot is about the same, suggesting that the processes of conductivity and relaxation for the charge carriers are the same.
This paper was presented at the International Conference on Solid State Science and Technology 2006, Kuala Terengganu, Malaysia,
Sept. 4–6, 2006. 相似文献
8.
Results of temperature and frequency dependent a.c. conductivity of pure and nickel-doped a-As2S3 are reported. The a.c. conductivity of pure As2S3 obeys a well-known relationship: σac ∝ω
s. Frequency exponents is found to decrease with increasing temperature. Correlated barrier hopping (CBH) model successfully explains the entire
behaviour of a.c. conductivity with respect to temperature and frequency for pure As2S3. But a different behaviour of a.c. conductivity has been observed for the nickel doped As2S3. At higher temperatures, distinct peaks have been observed in the plots of temperature dependence of a.c. conductivity. The
frequency dependent behaviour of a.c. conductivity (σac ∝ω
s) for nickeldoped As2S3 is similar to pure As2S3 at lower temperatures. But at higher temperatures, ln σac vs lnf curves have been found to deviate from linearity. Such a behaviour has been explained by assuming that nickel doping gives
rise to some neutral defect states (D
0′) in the band gap. Single polaron hopping is expected to occur between theseD
0‘ andD
+ states. Furthermore, allD
+,D
0′ pairs are assumed to be equivalent, having a fixed relaxation time at a given temperature. The contribution of this relaxation
to a.c. conductivity is found to be responsible for the observed peak in the plots of temperature dependence of a.c. conductivity
for nickel-doped As2S3. The entire behaviour of a.c. conductivity with respect to temperature and frequency has been explained by using CBH and
“simple pair” models. Theoretical results obtained by using these models, have been found to be in agreement with the experimental
results. 相似文献
9.
A. V. Shil’nikov V. A. Fedorikhin A. P. Pozdnyakov A. V. Sopit L. A. Shuvalov 《Physics of the Solid State》1999,41(6):977-979
The complex permittivity ɛ* is studied with separate readings for ɛ′ and ɛ″ at low and infralow frequencies and ultraweak fields. The effective conductivity λ is determined. An Arrhenius dependence is observed for ln ɛ′(1/T), ln ɛ″(1/T), and ln λ(1/T), both in the paraphase and in the polar phase. It is proposed that the conductivity of crystalline DTGS in the paraphase
is an ion jump conductivity.
Fiz. Tverd. Tela (St. Petersburg) 41, 1073–1075 (June 1999) 相似文献
10.
The behavior of the thermal conductivity k(T) of bulk faceted fullerite C60 crystals is investigated at temperatures T=8–220 K. The samples are prepared by the gas-transport method from pure C60, containing less than 0.01% impurities. It is found that as the temperature decreases, the thermal conductivity of the crystal
increases, reaches a maximum at T=15–20 K, and drops by a factor of ∼2, proportional to the change in the specific heat, on cooling to 8 K. The effective phonon
mean free path λ
p, estimated from the thermal conductivity and known from the published values of the specific heat of fullerite, is comparable
to the lattice constant of the crystal λ
p∼d=1.4 nm at temperatures T>200 K and reaches values λp∼50d at T<15 K, i.e., the maximum phonon ranges are limited by scattering on defects in the volume of the sample in the simple cubic
phase. In the range T=25−75 K the observed temperature dependence k(T) can be described by the expression k(T)∼exp(Θ/bT), characteristic for the behavior of the thermal conductivity of perfect nonconducting crystals at temperatures below the
Debye temperature Θ (Θ=80 K in fullerite), where umklapp phonon-phonon scattering processes predominate in the volume of the
sample.
Pis’ma Zh. éksp. Teor. Fiz. 65, No. 8, 651–656 (25 April 1997) 相似文献
11.
An expression for the fourth moment of the line profile in terms of several strain derivatives and the possibility of measuring
the ‘wavelength’ of crystal distortions (λ) for any sinusoidally varying component of the strain are available. The experimental means for evaluating such strain derivatives
in the expression for the fourth moment was earlier described. A numerical method for evaluating this wavelength and its subsequent
use to determineλ in several samples ofα-brass is presented here. The data used are taken from the earlier paper of the authors. An attempt has been made to interpret
the values ofλ and their changes with cold working and annealing in terms of lattice strain. 相似文献
12.
The temperature dependence of the electrical conductivity, thermoelectric power and dielectric constant of the antiferromagnetic
CuWO4 have been studied in the temperature range 300–1000 K. The conductivity results can be summarised by the equations σI=6.31 × 10−3 exp (−0.29 eV/kT) ohm−1 cm−1 in the temperature range 300–600 K and σII=3.16 × 105 exp (−1.48 eV/kT) ohm−1 cm−1 between 600 K and 1000 K. The thermoelectric power can be expressed byθ=[− 1.25 (103/T) + 3.9] mV/K. Initially dielectric constant increases slowly but for high temperatures its increase is fast. 相似文献
13.
Alexander S. Bulatov Viktor F. Dolzenko Anatoli V. Kornietz 《Czechoslovak Journal of Physics》1996,46(Z4):2119-2120
Information on the character of the temperature relationships of linear expansion coefficients (αa, αc) and exchange magnetostrictions (λa, λa) of single crystal Ho and Dy, based on temperature dependence of thec- anda-axis lattice constants, were accurately determined by X-ray diffraction from 4,2 to 300 K. In the helical phases we observed
a large anisotropy of expansion coefficients (αa>0, αc<0) and their variations at 24,5, 45 and 96 in Ho and 156 K in Dy. These anomalies were caused by the commensurate transitions.
The Curie transition in Ho is found to be of the 1-st order. 相似文献
14.
Alessandra Iacobucci Frédéric Legoll Stefano Olla Gabriel Stoltz 《Journal of statistical physics》2010,140(2):336-348
We study the thermal conductivity of the one dimensional Toda lattice perturbed by a stochastic dynamics preserving energy
and momentum. The strength of the stochastic noise is controlled by a parameter γ. We show that heat transport is anomalous, and that the thermal conductivity diverges with the length n of the chain according to κ(n)∼n
α
, with 0<α≤1/2. In particular, the ballistic heat conduction of the unperturbed Toda chain is destroyed. Besides, the exponent α of the divergence depends on γ. 相似文献
15.
E. A. Kataeva A. D. Bozhko S. V. Demishev 《Bulletin of the Lebedev Physics Institute》2010,37(11):347-351
The conductivity of carbon films grown by polymethylphenylsiloxane vapor decomposition in stimulated dc discharge plasma was
studied. It is found that the Mott hopping conductivity $
\sigma \left( T \right) = \sigma _0 \left( T \right)\exp \left\{ { - \frac{{T_0 }}
{T}^{{1 \mathord{\left/
{\vphantom {1 4}} \right.
\kern-\nulldelimiterspace} 4}} } \right\}
$
\sigma \left( T \right) = \sigma _0 \left( T \right)\exp \left\{ { - \frac{{T_0 }}
{T}^{{1 \mathord{\left/
{\vphantom {1 4}} \right.
\kern-\nulldelimiterspace} 4}} } \right\}
is characteristic of the samples under study in the temperature range of 80–400 K in the electric field E to 5 · 104 V/cm. An analysis of the pre-exponential factor σ
0(T) = σ
00(T
0)T
α allowed the conclusion that the hopping transport is most adequately described in the model with the exponential energy dependence
of the density of localized states for which α = −1/2 and the universal relation ln σ
00 −T
01/4 0 is valid, which is satisfied in the range where the parameter σ
00 varies by eight orders of magnitude. 相似文献
16.
B. Lalevic N. Fuschillo B. Kuliyev W. Wang 《Applied Physics A: Materials Science & Processing》1974,5(2):127-132
Transport and dielectric properties of polycrystalline CoO films were studied as functions of the applied field, frequency
and temperature. TheI–V plots showed that the Poole-Frenkel field emission mechanism is responsible for conduction at fields>105 V/cm. The ac conductivity σ(ω), the imaginary part of the dielectric constantε
2, and tan δ plots as functions of frequency revealed three dispersion regions. The σ(ω) andε
2 frequency dependence indicates a non-adiabatic hopping of charge carriers at low frequencies and adiabatic hopping at high
frequencies. The activation energy of a dielectric oscillator is 0.15 eV.
Work supported by the Office of Naval Research. 相似文献
17.
The temperature dependences of the Seebeck coefficient α and of the electrical conductivity σ of p-Bi2−x
SbxTe3−y
Sey solid solutions were studied under atomic substitution on the cation (1 ≤ x ≤ 1.5) and anion (0.04 ≤ y ≤ 0.09) bismuth and antimony telluride sublattices within the temperature interval 80–340 K. The effect of variation in the
solid-solution composition on the average effective density-of-states mass (m/m
0) and carrier mobility (μ0, calculated with due account of degeneracy) was studied under the assumption that carrier scattering is isotropic and that
the relaxation time can be approximated by a power-law function
, where r
eff is an effective scattering parameter. It is shown that variations in the pattern of the m/m
0 and μ0 temperature dependences produced in the temperature region under study by properly varying the number of substituted atoms
in the solid solutions may favor an increase in thermoelectric efficiency.
__________
Translated from Fizika Tverdogo Tela, Vol. 47, No. 2, 2005, pp. 224–228.
Original Russian Text Copyright ? 2005 by Luk’yanova, Kutasov, Konstantinov. 相似文献
18.
Y.Z. Pei L.D. Chen X.Y. Zhao W.Q. Zhang X.Y. Li T. Goto 《Applied Physics A: Materials Science & Processing》2006,85(4):451-455
Polycrystalline skutterudite solid solutions, Ba0.3 (IrxCo1-x)4Sb12 (x from 0 to 0.11), have been synthesized by a two-step solid state reaction method and sintered by a spark plasma sintering
(SPS) technique. The influence of Ir substitution on electrical and thermal transport properties has been investigated in
the temperature range of 300–850 K. Through Ir substitution, the lattice thermal conductivity was depressed due to the phonon
scattering by point defects. The thermopower and thermoelectric power factor increased because of the enhancement of carrier
acoustic lattice scattering especially at lower temperatures. Both the dimensionless figure of merit (ZT) and the thermoelectric
compatibility factor (CF), which play very important roles for applications, were improved over the whole temperature region.
PACS 72.15.Eb; 72.15.Jf; 72.20.Pa; 63.20.Mt; 74.25.Fy
An erratum to this article can be found at 相似文献
19.
The thermal conductivity of diamond-paraffin wax composites prepared by infiltration of a hydrocarbon binder with the thermal
conductivity λ
m
= 0.2 W m−1 K−1 into a dense bed of diamond particles (λ
f
∼ 1500 W m−1 K−1) with sizes of 400 and 180 μm has been investigated. The calculations using universally accepted models considering isolated
inclusions in a matrix have demonstrated that the best agreement with the measured values of the thermal conductivity of the
composite λ = 10–12 W m−1 K−1 is achieved with the use of the differential effective medium model, the Maxwell mean field scheme gives a very underestimated
calculated value of λ, and the effective medium theory leads to a very overestimated value. An agreement between the calculation
and the experiment can be provided by constructing thermal conductivity functions. The calculation of the thermal conductivity
at the percolation threshold has shown that the experimental thermal conductivity of the composites is higher than this critical
value. It has been established that, for the composites with closely packed diamond particles (the volume fraction is ∼0.63
for a monodisperse binder), the use of the isolated particle model (Hasselman-Johnson and differential effective medium models)
for calculating the thermal conductivity is not quite correct, because the model does not take into account the percolation
component of the thermal conductivity. In particular, this holds true for the calculation of the heat conductance of diamond-matrix
interfaces in diamond-metal composites with a high thermal conductivity. 相似文献
20.
M. G. Ramazanzade S. A. Aliev N. A. Berdieva A. M. Agaev 《Russian Physics Journal》1981,24(10):919-923
To obtain information on the temperature and concentration dependence of thermoelectric quality factor Z and to clarify the nature of scattering in Ag2Se a study was made of electrical conductivity , thermo-emf , and thermal conductivity in silver selenide over the temperature range T=80–450°K at concentration levels of 2–43·1024 m–3. It is shown that in Ag2Se the Lorentz number L, determined experimentally from the electronic fraction of the thermal conductivity, is less than the Sommerfeld number Lo. Calculation of L/Lo(n) performed with a theory considering inelastic scattering of carriers, shows that the inelasticity is produced by electron interaction. Comparison of experimental data on the temperature dependence of lattice thermal conductivity with theory permits the conclusion that in Ag2Se in range 80–300°K the basic role in phonon scattering is played by three-phonon Umklapp processes. It is shown that with increase in T and decrease in n the thermoelectric quality factor of silver selenide increases. The highest value of Z was achieved in a specimen with electron concentration n=2·1024 m–3 at T=320°K. The rapid decrease in Z upon phase transition is related to discontinuous decrease in and at this point.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 27–31, October, 1981. 相似文献