Showing papers on "Seebeck coefficient published in 1970"
TL;DR: In this article, an attempt is made to establish the nature of free charge carriers and of charge carriers bound to centres in p-type NiO, CoO, and MnO and in n-type MnO, α-Fe2O3.
Abstract: In this paper an attempt is made to establish the nature of free charge carriers and of charge carriers bound to centres in p-type NiO, CoO and MnO and in n-type MnO and α-Fe2O3. For free charge carriers, d.c. conductivity, Seebeck coefficient and Hall effect are considered. Effects arising from inhomogeneous conduction and impurity conduction are discussed. Impurity conduction appears to have a strong influence on transport properties in the case of α-Fe2O3, less so in NiO, whereas no influence of this effect has been found in CoO and MnO. It is shown that NiO and CoO do not exhibit the features characteristic of small-polaron conductors but rather can be consistently conceived of as large-polaron band semiconductors. It is suggested that magnetic resistance due to exchange coupling between charge-carrier spin and cation spins plays an important role. The anomalous behaviour of the Hall effect in NiO and α-Fe2O3 is extensively discussed. In contradistinction to NiO, CoO and n-type MnO, free char...
544 citations
TL;DR: In this article, the authors investigated the thermoelectric power behavior of tungsten trioxide in the presence of oxygen deficiency and showed that the defect unit is not the oxygen vacancy but the Anderson-Hyde disk of shear.
240 citations
TL;DR: In this article, the dc and ac conductivities and thermoelectric power have been measured as a function of the ratio (V 4+ /V total ) in glasses in the system V 2 O 5 -P 2 O5.
Abstract: The dc and ac conductivity and thermoelectric power have been measured as a function of the ratio (V 4+ /V total ) in glasses in the system V 2 O 5 -P 2 O 5 . The conductivity goes through a maximum as the ratio (V 4+ /V total ) is varied but at a much lower value than that expected from a straightforward hopping model (i.e. 0.5) in which all sites contribute equally. The thermoelectric power tends to go through zero but at a different value of (V 4+ /V total ) than the maximum in conductivity. These discrepancies from simple behaviour may be connected with the structural complexity of the glass and at least two suggestions can be made to account for these deviations. The log conductivity versus (1/ T ) plots are not linear and their slopes decrease rapidly at low temperatures. Possible reasons for this behaviour are mentioned. The ac conductivity varies nearly linearly with frequency in the audio- to radio-frequency region and approximately as the square of frequency at higher frequencies. At the same time the high frequency conductivity tends to become independent of temperature. This is almost identical with similar observations in, for instance, chalcogenide glasses.
222 citations
TL;DR: In this article, the optical spectra of some semiconductors (Ge, InSb, Se, Te and As 2 Se 3 ) are reviewed for which the optical properties are known in a broad energy range both in the crystalline and the amorphous phase.
Abstract: The optical spectra are reviewed for some semiconductors (Ge, InSb, Se, Te and As 2 Se 3 ) for which the optical properties are known in a broad energy range both in the crystalline and the amorphous phase. In particular the change of the spectra on the transition to the disordered state is treated and the different behaviour of the semiconductors is discussed. Furthermore recent results on electroreflection are reported. The review of the electrical properties is mainly restricted to conductivity, thermoelectric power and some results on magneto- and piezoresistance. The main features of the intrinsic and the impurity conduction range are pointed out and the influence of impurity atoms and of structure defects are discussed. For the intrinsic conductivity a simple relation is given which is valid for most amorphous semiconductors.
197 citations
TL;DR: In this article, the dc and ac conductivity, thermoelectric power, optical absorption and carrier mobility of As2S3, As2Se3 and some other chalcogenide glasses are described and discussed.
Abstract: The dc and ac conductivity, thermoelectric power, optical absorption and carrier mobility of As2S3, As2Se3 and some other chalcogenide glasses are described and discussed. The question of band or hopping conduction is considered and it is concluded that although the ac conductivity involves hopping, the dc properties are best viewed in terms of a band model with a “mobility gap” as introduced by Mott and Cohen. There are, however, some unresolved problems, particularly relating to the ac conductivity.
118 citations
TL;DR: In this article, the authors used the hopping model and small polaron theory to understand the mechanism of conduction in rare earth sesquioxides and nonstoichiometric oxides of rare-earths.
97 citations
TL;DR: In this article, the classification of liquid alloys into two types, one appreciably more metallic in character than the other, is described in terms of the properties of the liquid MgBi, which undergoes a transition from metallic to non-metallic behaviour near the composition Mg3 Bi2.
Abstract: The classification of liquid alloys into two types, one appreciably more metallic in character than the other, is described in this paper. Attention is focussed on liquid MgBi, whose electronic properties may be followed continuously across the phase diagram, and which undergoes a transition from metallic to non-metallic behaviour near the composition Mg3 Bi2. New data for both the conductivity, σ, and the thermoelectric power, S, are presented. σ falls to a very low value ( ⋍ 45 Ω −1 cm −1 ) at the composition Mg3Bi2 whilst dσ/dT is positive. S goes from positive to negative as the composition is changed from Mg3Bi2 + Bi toMg3Bi2 + Mg. Thus the electrical properties of this system closely resemble those previously found for liquid TeTl. A brief account of the data in terms of a model involving strongly energy dependent scattering is given.
61 citations
TL;DR: In this paper, the Mott model for s-d scattering was used to calculate the electrical resistivity, thermal conductivity, and thermoelectric power at high temperatures for palladium, platinum, rhodium, iridium, molybdenum, and tungsten, by making use of the density of states determined in the rigid band model from the data of low temperature specific heat coefficients.
Abstract: In the Mott model for s - d scattering, the electrical resistivity, thermal conductivity, and thermoelectric power are calculated at high temperatures for palladium, platinum, rhodium, iridium, molybdenum, and tungsten, by assuming proper electronic structures, and making use of the density of states determined in the rigid band model from the data of low temperature specific heat coefficients. The results are compared with experiments. The calculated temperature dependences of electrical resistivity, thermal conductivity, and thermoelectric power at high temperatures are found to be strongly dependent on the shape of the density of states and the position of the Fermi level. All of these temperature dependences are consistent with the experimental results. It is confirmed that there is a strong correlation between these temperature dependences and those of electronic specific heat coefficient and spin susceptibility.
58 citations
TL;DR: In this paper, experimental values of the thermal conductivity and thermoelectric power of n-type silicon doped with phosphorus, antimony or arsenic, containing 4*1019 to 6*1025 m-3 electrons at room temperature, covering the range 4-300 degrees K.
Abstract: Experimental values are given of the thermal conductivity and thermoelectric power of n-type silicon doped with phosphorus, antimony or arsenic, containing 4*1019 to 6*1025 m-3 electrons at room temperature, covering the range 4-300 degrees K. A theoretical treatment, using the variational method, suggests that the ratio of phonon drag component of thermoelectric power to thermal conductivity should be independent of carrier concentration, if the latter is not too large. This is verified experimentally; the temperature variation of the ratio is in satisfactory agreement with theory, which also gives the correct order of magnitude for the absolute value.
58 citations
TL;DR: In this paper, a temperature-independent Seebeck coefficient for polaron charge carriers θ ± = ± 198 log (n-p)/p, where the polaron concentration p can be determined from chemistry and the concentration N of available polaron sites is model-dependent.
53 citations
TL;DR: In this article, anomalies in the normal state electrical resistivity, thermoelectric power, and magnetic susceptibility have been observed in dilute alloys of uranium dissolved in thorium and these anomalies appear to be due to localized spin fluctuations with a characteristic temperatureT 0 ∼ 100K which are associated with 5f virtual bound states on the U atoms.
Abstract: Anomalies in the normal-state electrical resistivity, thermoelectric power, and magnetic susceptibility have been observed in dilute alloys of uranium dissolved in thorium. These anomalies appear to be due to localized spin fluctuations with a characteristic temperatureT0 ∼ 100K which are associated with5f virtual bound states on the U atoms. The depression of the superconducting transition temperature of Th by U impurities is large and deviates markedly from the form given by the Abrikosov-Gor'kov theory.
TL;DR: In this paper, the electron and hole trapping levels of high density of states determine essentially the conductivity mechanism of β-rhombohedral boron, and the ionization energy of trapped electrons is much greater than that of trapped holes; so, up to high temperatures, the electrons do not appreciably contribute to the charge transport.
Abstract: Electron and hole trapping levels of high density of states determine essentially the conductivity mechanism of β-rhombohedral boron. The ionization energy of trapped electrons is much greater than that of trapped holes; so, up to high temperatures, the electrons do not appreciably contribute to the charge transport. From electrical conductivity and thermoelectric power at higher temperatures one obtains the activation energy of the hole mobility (0.19 eV). At low temperatures hopping within the hole trapping level seems to be the prevailing conductivity mechanism.
TL;DR: In this article, a 2-energy-level model is proposed for the Fe2+ ions, which removes most, though not all, discrepancies between predicted and experimental results, and shows a transition from a temperature independent region to a temperature activated region.
Abstract: Measurements are reported of the resistivity and the thermoelectric power as a function of temperature for nickel-iron ferrites. The thermoelectric power shows a transition from a temperature independent to a temperature activated region. The results are broadly in agreement with the Jonker hopping model but some disagreement with the accepted simple theory is found. A 2-energy-level model is proposed for the Fe2+ ions; this removes most, though not all, discrepancies between predicted and experimental results.
TL;DR: In this paper, the thermal conductivity, thermoelectric power and electrical resistivity for a series of 20 annealed polycrystalline Ag-Au alloys, covering the whole 100% α-solid solution range of the system, have been measured from 3° to 300°k.
Abstract: The thermal conductivity, thermoelectric power and electrical resistivity for a series of 20 annealed polycrystalline Ag—Au alloys, covering the whole 100% α-solid solution range of the system, have been measured from 3° to 300°k. The thermoelectric power has been separated into diffusion and phonon drag components and the effect of Fe impurities has been taken into account. The attenuation of the phonon drag peak on alloying cannot be explained simply by the corresponding attenuation of the lattice component of the thermal conductivity, nor does it show the resurgence at high solute concentrations previously observed in other noble metal alloy systems.
TL;DR: In this article, the ability of thermoelectric power measurements to permit a description of carrier density and phonon-drag variations caused by photoexcitation was tested in 100−Ω·cm n and p-type silicon.
Abstract: The ability of thermoelectric power measurements to permit a description of carrier‐density and phonon‐drag variations caused by photoexcitation was tested in 100‐Ω·cm n‐ and p‐type silicon. At low temperatures the major effect of photexcitation is to decrease the phonon‐drag contribution to the thermoelectric power by increasing the phonon density in the crystal. At higher temperatures the thermoelectric effect can be used to investigate changes in the electronic contribution due to photoexcitation. An apparently anomalous increase in thermoelectric power with photoexcitation was consistently found in p‐type silicon over an intermediate temperature range.
TL;DR: In this article, the authors studied the thermoelectric power of metals containing magnetic impurities with crystal-field split energy levels, and showed that anomalous contributions arise, whose size can be nearly comparable with that found in the Kondo problem.
Abstract: We study the thermoelectric power of metals containing magnetic impurities with crystal-field split energy levels. Of special interest is the case where the ground state is a nonmagnetic singlet. It is shown that anomalous contributions arise, whose size can be nearly comparable with that found in the Kondo problem. However the mechanism leading to these effects is very different in the present problem, since it results from differences in the thermal population of the impurity levels. Also the anomalous contributions appear in a lower order of perturbation theory than they do in the corresponding Kondo problem calculations.
TL;DR: In this paper, the authors measured the thermal conductivity, λ(80° to 400°K), electrical resistivity, ρ(4.2° to 300°K) and absolute Seebeck coefficient of pressed and sintered uranium mononitride.
Abstract: Measurements are reported for the thermal conductivity, λ(80° to 400°K), electrical resistivity, ρ(4.2° to 400°K), and absolute Seebeck coefficient, Q(6° to 400°K), of pressed and sintered uranium mononitride. The measurements between 77° and 400°K were made using an absolute longitudinal heat flow apparatus. These data and literature values for the thermal conductivity and electrical resistivity at higher temperatures were used to separate the electronic and lattice portions of the thermal conductivity. The results indicate that the lattice conductivity peaks in the range 250° to 300°K and that the high-temperature limit of the Lorenz function may be greater than the Sommerfeld value of 2.443 × 10-8 (V2°K-2). The electrical resistivity and the absolute Seebeck coefficient exhibit sharp slope changes near the Neel temperature, TN(∼50° to 60°K). The Seebeck coefficient has a minimum at 34°K and then rises to a local maximum at 10°K. This low-temperature peak is probably due to magnon drag. The temperature dependence of the electrical resistivity is dominated by the magnetic contribution which increases as T2.38±0.08 between 10° and 52°K. The magnetic contribution is constant at high temperatures with an estimated value of 142 μΩ-cm.
TL;DR: In this article, the phonon-drag effects on σ and R are proved to be negligibly small, which may be attributed to the large s-d hybridization in Burdick's bands.
Abstract: The electrical conductivity σ, the phonon-drag thermoelectric power S L , and the low-field Hall coefficient R of copper are calculated with the variational method. The band structures of Burdick and the measured phonon spectrum are used in the calculation. The parameters in the electron-phonon coupling are adjusted to the observed electrical conductivity. The room-temperature value of R is smaller than the observed one by 20%, and this discrepancy may be ascribed to the large s - d hybridization in Burdick's bands. The temperature dependence of R agrees reasonably well with the observation above 50°K. It is noted that below 50°K, existing measurements for pure samples do not satisfy the low-field condition. The phonon-drag effects on σ and R are proved to be negligibly small. The calculated value of S L is positive above 30°K and large enough to explain the observed hump around 70°K, while it becomes negative below about 30°K, consistent with the experimental results.
TL;DR: In this paper, the temperature variation of the absolute thermoelectric power of pure nickel and its dilute alloys with Pd, Cu, Co, Fe, Mn, Cr, V and Ti was reported.
Abstract: Measurements are reported of the temperature variation of the absolute thermoelectric power of pure nickel and its dilute alloys with Pd, Cu, Co, Fe, Mn, Cr, V and Ti. Most of the data have been taken between 2 degrees K and 100 degrees K, although certain measurements have only been made between 2 degrees K and 15 degrees K. The curves taken over the wider temperature range all exhibit pronounced minima at about 40 degrees K, with the depth of the minima considerably greater in the Ni-Cu, Ni-Co and Ni-Fe alloys than in pure nickel. It is argued that this is due to the effect of spin-mixing on the phonon drag component of thermopower. There is a discussion of the likely influence of spin- mixing on the diffusion thermopower.
TL;DR: In this article, the electrical resistivity p ancl the Seebeck coefficient S at temperatures up to 850°c in the range in which the two liquid phases are mutually soluble in orcler to study the transition between metallic and semiconductor behaviour.
Abstract: In the composition range 70 to 100 atomic % thallium, the phase diagram of Tl[sbnd]Te has a region with two immiscible phases below 600°c, corresponding to the separation of a metallic and a liquid semiconductor phase. We have made measurements of the electrical resistivity p ancl the Seebeck coefficient S at temperatures up to 850°c in the range in which the two liquid phases are mutually soluble in orcler to study the transition between metallic and semiconductor behaviour. As the concentration of tellurium is increased, p and the magnitude of S increase, and their temperature coefficients change from weakly positive values typical of metals to weakly negative values typical of liquid semiconductors with low resistivity. We find that the transport behaviour can be accounted for very well by a model which treats the alloy as a solution containing Tl2Te molecules plus metallic TI atoms. As Te is added to Tl2 electrons are removed from the conduction band, and scattering centres due to Tl2Te are a...
TL;DR: A phase transformation in EU3S4 at 168°K has been established by several different experimental methods as mentioned in this paper, which is due to charge ordering which produces tetragonal symmetry in the unit cell.
Abstract: A phase transformation in EU3S4 at 168°K has been established by several different experimental methods. Electrical conductivity and Seebeck coefficient measurements show a discontinuity through the transition. Above the transition temperature, the activation energy for conduction is 0.163 eV and the resistivity is about 3 × 10 4 Ωcm , while below the transition the activation energy is 0.21 eV and the resistivity is about 106 Ωcm. Differential thermal analysis thermograms reveal an endothermic peak on heating with a hysteresis of 5°C. X-ray diffraction experiments show a change in symmetry accompanied by a lattice parameter change of approximately 0.4% for the transition. Measurements of the magnetic susceptibility show the transition not to be magnetic in origin. It is proposed that the transformation in EU3S4 is due to charge ordering which produces tetragonal symmetry in the unit cell.
TL;DR: In this article, combined electrical conductivity and thermoelectric power measurements have been made on Eu3S4 at temperatures from 100° to 1000°K, and the Seebeck coefficient data obtained are interpreted in terms of the contribution of the kinetic energy term and the influence of the high charge carrier density on the concentration of available sites.
Abstract: Combined electrical conductivity and thermoelectric power measurements have been made on Eu3S4 at temperatures from 100° to 1000°K. These measurements show that the charge carrier concentration in this temperature range is essentially constant. The activation energy for electrical conduction arises, therefore, from the temperature dependence of the drift mobility, and is interpreted as an energy required for the hopping motion of the electronic charge carriers. An abrupt change in resistivity, characteristic of a transition, occurs at about 175°K. The activation energy for conduction above and below the transition is 0.163±0.004 eV and 0.21±0.01 eV, respectively. The Seebeck coefficient data obtained are interpreted in terms of the contribution of the kinetic energy term and the influence of the high charge carrier density on the concentration of available sites.
IBM1
TL;DR: The dc resistivity of nickel-zinc ferrite was studied as a function of nickel/zinc ratio, apparent density, temperature, and grain size in this article, where the dc resistivities of Ni0.40Zn0.65-Fe1.90O4 were compared.
Abstract: The dc resistivity of nickel-zinc ferrite was studied as a function of nickel/zinc ratio, apparent density, temperature, and grain size. Resistivities of Ni0.40Zn0.51Fe1.90O4– and Ni0.35Zn0.65-Fe1.90O4– are similar. Evaluation of samples sintered between 1100° and 1220°C showed that densification proceeds rapidly for sintering temperatures 1170°C; for these specimens the room temperature resistivity increases to an equilibrium value with sintering time. Samples sintered to 99+% of theoretical density at lower temperatures densify slowly; the resistivity is invariant with sintering time. The Seebeck coefficient for the p-type ferrites is 550 μV/°C from 200° to 700°C; the dielectric constant varies from 17.3 at 0.5 MHz to 16.4 at 15 MHz.
TL;DR: In this article, the magnetic properties and the electrical resistivity, the Hall effect, the thermoelectric power, and the magnetoresistance were carried out on polycrystalline rhombohedral Cr2S3.
TL;DR: In this article, conductivity and Seebeck coefficient measurements have been made on commerically available molded PVC samples containing a range of impurities and on much purer specimens recast from tetrahydrofuran solution.
Abstract: Conductivity and Seebeck coefficient measurements have been made on commerically-available molded PVC samples containing a range of impurities and on much purer specimens recast from tetrahydrofuran solution. Activation energies measured in the latter materials were not very reproducible; it seems likely that the evaporation of gold electrodes thermally initiates a dehydrochlorination reaction which renders the samples unstable. A range of activation energies from 1.4 to 1.8 eV was observed in the impure samples. The Seebeck coefficient measurements indicated that the majority carriers were negatively charged; the linearity of the current-voltage relationship up to applied field strengths of 80,000 V/cm then suggested an electronic conduction mechanism, although considerable polarization effects were observed in both pure and impure samples. The Seebeck coefficient results also showed that even the purest PVC obtainable is unlikely to be an intrinsic semiconductor, and that the electron transport...
TL;DR: In this paper, resistance marker measurements were carried out between 230 and 400°C and it was concluded that the oxide grows by metal transport and from the sign of its Seebeck coefficient, the oxide was deduced to ben-type.
Abstract: This paper describes some oxidation studies of evaporated aluminum films. Resistance marker measurements were carried out between 230 and 400° C and it was concluded that the oxide grows by metal transport. From the sign of its Seebeck coefficient, the oxide was deduced to ben-type. The effect of applying an electric field across the growing oxide layer on aluminum was also investigated. A porous platinum layer evaporated onto the oxide surface was used as one electrode, the underlying metal being the other electrode. At all temperatures between 50 and 400° C the same field effect was observed. When the oxygen-oxide interface was biased negative with respect to the aluminum, an enhancement of the oxidation rate was achieved. These results have been interpreted in terms of the Mott-Cabrera theory.
TL;DR: The mechanism of electrical conduction in the magnetic semiconductors NixFe3-xO4 with 0.6 < x ≤ 1 was investigated in this article, where the exponential temperature dependence of the electrical resistivity ρ and the temperature independent thermoelectric power θ are in good agreement with an electron-hopping model.
Abstract: The mechanism of electrical conduction in the magnetic semiconductors NixFe3-xO4 with 0.6 < x ≤ 1 was investigated. The electrical properties of these compounds are extremely sensitive to the presence of α-Fe2O3 as a second phase. The exponential temperature dependence of the electrical resistivity ρ and the temperature-independent thermoelectric power θ are in good agreement with an electron-hopping model. The electrical conduction occurs by thermally activated electron hopping between octahedral Fe2+ and Fe3+ ions with an activation energy q. The values of ρ, q and θ depend on the Fe2+ concentration only, and are not sensitive to small deviations from stoichiometry due to the presence of cation or anion vacancies.
TL;DR: In this article, the authors measured the Seebeck coefficient and Curie point in reduced barium titanate and interpreted the results in terms of a polaron hopping model, leading to an estimated mobility of 5×10−4 cm2 V−1 sec−1 at 300° K and an activation energy of 0.074 eV.
Abstract: The conductivity, Seebeck coefficient and Curie point have been measured in reduced crystals of barium titanate. The results have been interpreted in terms of a polaron hopping model, leading to an estimated mobility of 5×10−4 cm2 V−1 sec−1 at 300° K, and an activation energy of 0.074 eV. The Curie point falls as a result of reduction, probably due to the formation of oxygen vacancies. The decrease can be correlated with the changes in conductivity through the estimated carrier density.
TL;DR: A series of measurements of Hall effect, thermoelectric power and electrical conductivity have been performed on the vitreous CdGexAs2 having a Ge content of 0.2, 0.3 and 0.4 as mentioned in this paper.
Abstract: A series of measurements of Hall effect, thermoelectric power and electrical conductivity have been performed on the vitreous CdGexAs2 having a Ge content of 0.2, 0.3, 0.4, 0.6 and 1 mol respectively. The electrical conductivity has an exponential behaviour in the temperature range 185–500 K only for the 0.6 and 1 mol composition. It deviates from the exponential behaviour at lower temperatures for the 0.2, 0.3 and 0.4 compositions. The thermoelectric power is positive for CdGe0.2As2, negative for CdGe0.6As2 and CdGe1.0As2, whereas it changes sign for CdGe0.3As2 and CdGe0.4As2. The Hall coefficient is negative for alll compositions except for the CdGe1.0As2. The Hall mobilities differ widely for the different compositions and have the values of 1.5 × 10–2 to 1.3 × 10–1 cm2 V–1 s–1 at room temperature.