Showing papers on "Seebeck coefficient published in 1985"
TL;DR: A new oxygen defect perovskite BaLa4Cu5O13.4, characterized by a mixed valence of copper has been isolated; the parameters of the tetragonal cell are closely related to that of the cubic perovsite:a = 8.644(4) A = a p 5√ and c = 3.867(3) A= a p as discussed by the authors.
149 citations
TL;DR: In this article, the metal-insulator transition upon pH variation has been investigated in polyaniline samples equilibrated at different pH levels, and it has been shown that the metal insulator becomes metal-conductivity, thermoelectric power, spin concentration and spin dynamics changes with pH variation.
Abstract: Conductivity, thermoelectric power, spin concentration and spin dynamics has been measured in polyaniline samples equilibrated at different pH. Data provide evidence for Metal-Insulator transition upon pH variation.
140 citations
TL;DR: In this paper, the Seebeck coefficient was measured using an analog subtraction circuit on an X-Y recorder, and the results showed that the error of measurements of the seebeck coefficient is less than + or - 1 percent.
Abstract: A high-temperature (1900 K) Seebeck coefficient apparatus is described in which small thermal gradients are generated in a sample by light pulses transmitted via light pipes. By employing an analog subtraction circuit, the Seebeck coefficient is displayed directly on an X-Y recorder. This technique presents a convenient, accurate, and rapid method for measuring the Seebeck coefficient in highly doped semiconductors as a function of temperature. The nature of the resulting display (X-Y recording) is a valuable tool in determining validity of the data. A straight line results (i.e., a minimum of hysteresis) only if all potential experimental errors are minimized. Under these conditions, the error of measurements of the Seebeck coefficient is estimated to be less than + or - 1 percent.
139 citations
TL;DR: In this article, electrical conductivity and thermoelectric power are studied in electrochemically prepared and doped polythiophene films, and the contribution of Pauli-paramagnetism to the spin sensitivity and the positive thermoeðric power is observed at heavily doped region.
Abstract: Electron spin resonance (ESR), electrical conductivity and thermoelectric power are studied in electrochemically prepared and doped polythiophene films. The ESR spin density increases by two orders of magnitude up to dopant concentration of ca. 3 mol%, then decreases, while the conductivity increases drastically by more than ten orders of magnitude until this doping level, followed by a rather mild increase. The ESR linewidth decreases sharply from 9 G to 0.4 G upon slight doping with shape change from Gaussian to Lorenzian. The contribution of Pauli-paramagnetism to the spin succeptibility and the positive thermoelectric power of ca. 20 µV/K which depends linearly on the temperature are observed at heavily doped region. These results are discussed in terms of shallow and deep polarons, and formation of bipolaron up to intermediate doping levels and the hole conduction at the metallic regime.
132 citations
TL;DR: In this article, the resistivity and thermoelectric power of intermediate valent CeNi x intermetallic compounds and their La homologs were determined in the temperature ranges 1.5 to 350 K and 1000 K, respectively.
103 citations
TL;DR: In this paper, thin films of bismuth telluride have been prepared by the reactive evaporation method and their properties such as conductivity, Hall effect, and thermoelectric power were studied in the temperature range from liquid nitrogen to 350 K. The films were of n-type with a carrier concentration of 1.25 x 10 20 at room temperature.
67 citations
TL;DR: In this article, the Thomson coefficient of platinum and tungsten was measured from 900 to 1600 K and the absolute thermopower of each wire was calculated using an optical pyrometer.
Abstract: We have measured the Thomson coefficient μ of platinum and tungsten from 900 to 1600 K and calculated the absolute thermopower S of each We describe a numerical technique for evaluating the temperature profile of a wire which is undergoing self-heating by direct current and discuss the experimental design problems associated with measuring μ at high temperatures We develop a method in which the direction of the current through the specimen is reversed about once per second and observe the rates of heating and cooling at different places with an optical pyrometer By changing the magnitude of the current at the same time as its reversal the change in the Joule heating is balanced with the change in the Thomson heating We describe a technique for calibrating the pyrometer, report measurements of μPL and μW, calculate S Pt and S w, and test the results according to Kelvin's relation, S = f μ/T dT The difference between our S Pt, and that given by Cusack and Kendall (1958) varies from −0·7μV K−1
64 citations
TL;DR: In this paper, the Seebeck coefficient, electrical resistivity, thermal conductivity, and Hall effect have been studied in gamma-phase La(3-x)S4(LaS/y/) for compositions with x in the range from 0.04 to 0.0005 per K at a composition x = 0.3, y = 1.48 (LaS /1.48/) was obtained.
Abstract: The Seebeck coefficient, electrical resistivity, thermal conductivity, and Hall effect have been studied in gamma-phase La(3-x)S4(LaS/y/) for compositions with x in the range from 0.04 to 0.3 (y in the range from 1.35 to 1.48) in order to ascertain its suitability for high-temperature (300 to 1400 K) thermoelectric energy conversion. In this temperature and composition range the material behaves as an extrinsic semiconductor whose degenerate carrier concentration is controlled by the stoichiometric ratio of La to S. A maximum figure-of-merit (Z) of approximately 0.0005 per K at a composition x = 0.3, y = 1.48 (LaS/1.48/) was obtained.
64 citations
TL;DR: In this article, the electrical properties of polycrystalline Na x WO3 thin films in the range 0
Abstract: Measurements of the electrical properties of polycrystalline Na x WO3 thin films in the range 0
58 citations
TL;DR: In this article, specific heat, resistivity, thermal conductivity and thermoelectric power measurements are reported for the normal and superconducting regimes of the heavy-fermion superconductor UPt3.
Abstract: Specific heat, resistivity, thermal conductivity and thermoelectric power measurements are reported for the normal and superconducting regimes of the heavy-fermion superconductor UPt3. A comparison is made with uranium-based spin-fluctuation and cerium-based Kondo-lattice compounds.
58 citations
TL;DR: In this article, the authors present a model in which equilibrium transport in amorphous semiconductors is ordinarily dominated by contributions from localized states in the band tails, independent of the position of the Fermi energy.
Abstract: We present a model in which equilibrium transport in amorphous semiconductors is ordinarily dominated by contributions from localized states in the band tails, independent of the position of the Fermi energy. This results in carrier mobilities that appear to be thermally activated, due to the temperature dependence of the energy at which most of the transport occurs. The model resolves the problem of the observed differences between the activation energies of the electrical conductivity and the thermoelectric power in a natural way.
TL;DR: In this article, the electrical resistivity and absolute thermoelectric power of the dense Kondo compound CeCu2Si2 were measured under very high pressures and the results indicate a transition in the normal-state electronic properties around 20-30 kbar, from a strongly correlated Fermi-liquid regime (the so-called heavy-fermion state) into an IV phase.
TL;DR: In this paper, the conductivity of the Fe3O4 CoFe2O4 from 600 to 1300°C was calculated from high-temperature thermopower measurements on oxygen-stoichiometric specimens.
TL;DR: In this article, the electrical resistivity ϱ and the thermoelectric power of CeCu6 single crystals are strongly anisotropic and the inverse of the temperature of the Kondo resistivity maximum roughly scales the linear temperature coefficient B of ϱ as well as the residual value (ϱ0 ÷ B ÷ 1/Tmax).
TL;DR: In this paper, pressure-assisted reaction sintering (PARS) was used to prepare thermoelectric elements of the γ-phase lanthanum sesquisulfide solid solution alloys which exist over a wide homogeneity range: LaSy (1.33
Abstract: The pressure‐assisted reaction sintering (PARS) method was used to prepare thermoelectric elements of the γ‐phase lanthanum sesquisulfide solid solution alloys which exist over a wide homogeneity range: LaSy (1.33
TL;DR: In this paper, the effects of the starting material Ce and the crucible on the Kondo lattice formation of CeCu 6 have been studied through the measurements of the electrical resistivity, thermoelectric power, negative magnetoresistance and magnetic susceptibility.
Abstract: Impurity effects of the starting material Ce and the crucible on the Kondo lattice formation of CeCu 6 have been studied through the measurements of the electrical resistivity, thermoelectric power, negative magnetoresistance and magnetic susceptibility.
TL;DR: In this article, the effect of electron-electron interactions on the thermoelectric power for hopping transport in two and three dimensions is calculated in the low-temperature limit.
Abstract: The effect of electron-electron interactions on the thermoelectric power for hopping transport in two and three dimensions is calculated in the low-temperature limit. While the conductivity requires a very precise measurement to extract a temperature exponent with enough precision to determine the role of the interactions, it is shown that the thermopower behaviour will reflect the presence of interactions in an unambiguous manner. In contrast to a Mott variable-range hopping model where the thermopower decreases to zero as the temperature decreases (S=0 at T=0), the thermopower in an Efros interaction mode, should approach a non-zero constant as T to 0.
TL;DR: In this paper, the low-temperature behavior of the resistivity, thermal conductivity and thermoelectric power (TEP) was compared for three Kondo lattices, i.e. antiferromagnetic CeAl2, enhanced Pauli paramagnetic CCA3 and superconducting CCA2Si2, and they showed that coherence leads to a hitherto not observed change of sign in the TEP below T = 0.5 K.
TL;DR: In this article, the thermoelectric power of magnetic (cubic) metals taking into account the inelastic scattering of electrons by phonons and by localized spins was investigated.
TL;DR: In this article, the authors reported electrical transport studies of rare-earth vanadates (RVO4 with R = Ce, Pr, Nd, Sm, Eu and Gd), prepared by solid state reaction and characterized by X-ray diffraction studies.
Abstract: This paper reports electrical transport studies of rare-earth vanadates (RVO4 with R = Ce, Pr, Nd, Sm, Eu and Gd), prepared by solid state reaction and characterized by X-ray diffraction studies. TGA study (300 to 1200 K) shows no weight loss; possible phase transitions in the range 1075 to 1300 K have been indicated by DTA studies. All these vanadates are typical semiconducting compounds with room temperature electrical conductivity (σ) lying between 10−4 and 10−2Ω−1m−1. Measurements of σ and the Seebeck coefficient (S) are reported in the temperature interval 400 to 1200 K. Two linear regions 400 to T1K and T1 to T2K have been obtained from the log σ against T−1 as well as the S against T−1 plots followed by a peak around T3 and minima around T4K. T4>T3>T2>T1, are different for different vanadates. It has been concluded that in the interval 400 to T1K, conduction is of the extrinsic hopping type with Ce4+ in CeVO4, Pr4+ in PrVO4 and V4+ in Nd to Gd vanadates as dominant defect centres. In the temperature interval T1, to T2K, the conduction has been shown to be of the intrinsic band type in all vanadates with polarons of intermediate coupling strength as the dominant charge carriers. Above T2 all vanadates tend to become metallic, but before this is achieved the phase change makes the conductivity smaller. T4 is close enough to the temperature corresponding to the DTA peak to be termed the phase transition temperature.
TL;DR: In this paper, the authors apply percolation theory to the small polaron hopping regime and evaluate the thermoelectric power at low and high temperatures for a situation in which we have a symmetrical band of localized states with the Fermi level in the middle, and for an asymmetrical case in which there are multiple localized states above the level of fermi.
Abstract: Percolation-theoretic considerations have been used by various workers to evaluate the dc hopping conductivity and the thermoelectric power in disordered systems. We apply percolation theory to the small polaron hopping regime. Expressions for the thermoelectric power at low and high temperatures are obtained for a situation in which we have a symmetrical band of localized states with the Fermi level in the middle, and for an asymmetrical case in which we have a band of localized states above the Fermi level, and the conductivity for the low temperature case is evaluated. The correlation between bonds due to the energy of the common site is included in the present treatment.
TL;DR: In this article, the experimental measurements reported on the electrical resistivity, temperature coefficient of resistance and thermoelectric power of nineteen transition metal films have been reviewed, and theoretical models proposed so far to analyse these experimental results have been briefly summarized.
Abstract: Recent experimental measurements reported on the electrical resistivity, temperature coefficient of resistance and thermoelectric power of nineteen transition metal films have been reviewed. All the theoretical models proposed so far to analyse these experimental results have been briefly summarized. Some suggestions for further experimental study on transition metal films are outlined.
TL;DR: In this article, the normal phase of UPt3 is characterized by a high thermal conductivity with a strong T2 term, by a coherence length smaller than the mean free path, and by lower and upper critical fields H(0)c1∼60 Oe and Hc2( 0)∼26 kOe.
Abstract: Experiments on the normal phase of UPt3 show a large positive magnetoresistivity, almost temperature‐independent, linear in field, and a positive thermoelectric power which is not linear in temperature as T→0. The superconducting phase is characterized by a high thermal conductivity with a strong T2 term, by a coherence length smaller than the mean free path, and by lower and upper critical fields H(0)c1∼60 Oe and Hc2(0)∼26 kOe.
TL;DR: In this article, the thermoelectric power, thermal and electrical conductivity of boron phosphide grown by chemical vapor deposition of hydrogenated compounds were measured in the temperature range from room temperature to 1000 °C.
Abstract: The thermoelectric power, thermal and electrical conductivity of boron phosphide grown by chemical vapor deposition of hydrogenated compounds were measured in the temperature range from room temperature to 1000 °C and the figure of merit of boron phosphide was evaluated. The figure of merit of 8×10−4 deg−1 was obtained at 1000 °C. This is one of the largest figures of merit at 1000 °C that have ever been obtained.
TL;DR: In this article, X-ray diffraction, magnetic hysteresis, resistivity and thermoelectric power measurements were carried out at different temperatures for the system GexFe1-xNiCrO4(x=0.0, 0.2,0.4, 0.,6, 0,8 and 1.0), which crystallises with a spinel structure.
Abstract: The authors report here on X-ray diffraction, magnetic hysteresis, resistivity and thermoelectric power measurements carried out at different temperatures for the system GexFe1-xNiCrO4(x=0.0, 0.2, 0.4, 0.6, 0.8 and 1.0), which crystallises with a spinel structure. On the basis of the site-preference energy values of the individual cations (as given by Miller, and Smit and Wijn) the cation distribution is expected to be given by (Gax3+Fe1-x3+) (Ni2+Cr3+)-O4, the Ga3+ and Fe3+ ions being on the A sites and the Ni2+ and Cr3+ ions on the B sites, thus providing a selective A-site magnetic dilution with increasing x. The saturation magnetisation measurements indicate a canting of the B-site moments with an average canting angle that increases with x. Whereas the lattice is found to contract with x, the activation energy deduced from the resistivity plots and the Seebeck coefficient is found to increase with x. For a given x the resistivity decreases with temperature (T) and for a given T it increases with x. The Seebeck coefficient is found to be independent of the temperature. These results can be explained by assuming a small-polaron hopping mechanism to be responsible for the conductivity and thermoelectric effect observed in this system.
TL;DR: In this paper, LiNi-Mischferriten were investigated over the temperature range 300 to 520 K by thermal probe method and the Seebeck coefficient (Q) decreased while the carrier concentration (n) and the charge carrier mobility (μ) increased with the increasing temperature.
Abstract: Thermoelectric power studies are made of LiNi mixed ferrites over the temperature range 300 to 520 K by thermal probe method. The Seebeck coefficient (Q) is found to decrease while the carrier concentration (n) and the charge carrier mobility (μ) are found to increase with the increasing temperature. On the basis of these results an explanation for the conduction mechanism in LiNi mixed ferrites is suggested.
Es wird die Thermospannung in LiNi-Mischferriten im Temperaturbereich von 300 bis 520 K mittels Thermosonde untersucht. Der Seebeck-Koeffizient (Q) nimmt ab, wahrend die Ladungstragerkonzentration (n) und die Ladungstragerbeweglichkeit (μ) mit steigender Temperatur zunehmen. Auf der Grundlage dieser Ergebnisse wird eine Erklarung fur den Leitungsmechanismus in LiNi-Mischferriten vorgeschlagen.
TL;DR: In this paper, the d.c. conductivity and thermoelectric power of CrSiO thin films were investigated in the temperature region 4-300 K. The results are discussed with respect to the structure of the films and are compared with results for the binary system Si1−xCrx.
TL;DR: In this paper, the effects of the Ce 4f electron state on these two physical properties are discussed in connection with the Fermi liquid theory, and the electrical resistivity of Ce(In 1-x Sn x ) 3 and (Ce 1- x La x )In 3 is found to have various behaviours depending upon the C4f electron states, while the thermopower has a common behaviour throughout the samples.
TL;DR: In this paper, the authors studied the transport and specific heat properties of orthorhombic molybdenum oxide γ-Mo 4 0 11, which is a quasi-two-dimensional metal.
TL;DR: In this article, a theory of the thermoelectric power tensor of anisotropic ferromagnetic metals with localized magnetic moments starting from the Boltzmann equation and incorporating anisotropy effects due to the lattice structure is presented.