Showing papers on "Seebeck coefficient published in 1968"
TL;DR: In this article, the authors measured the Hall coefficient of β-FeSi2 doped with cobalt (n-type) or aluminium (p-type), and found that the activation energy of the mobility is 0.06 eV, the density of states N = 1.2 × 1022 cm−3.
Abstract: Electrical conductivity, thermoelectric power and Hall coefficient of β-FeSi2 doped with cobalt (n-type) or aluminium (p-type) are measured between 100 and 1200 °K. The conductivity of n-FeSi2 follows an exponential dependence on temperature. The temperature dependence of the thermoelectric power cannot be interpreted on the basis of conduction in a band. With the assumption that conduction in n-FeSi2 is caused by small polarons, the mobility at room temperature is found to be μn = 0.26 cm2/Vs. The activation energy of the mobility is 0.06 eV, the density of states N = 1.2 × 1022 cm−3. The electrical properties of p-FeSi2 can be interpreted using the band model with a hole mobility μp ≈ 2 cm2/Vs, which varies as T−1/2 in the region of extrinsic conduction. From intrinsic conduction a band gap of 0.9 to 1.0 eV is deduced. The disappearance of the thermoelectric power at high temperature is related to the semiconductor-to-metal transition at 1200 °K.
225 citations
TL;DR: In this article, a review of experimental data and the theoretical interpretation of these data on thermal transport and phonon scattering mechanisms in alloy semiconductors at high temperatures is given, with a focus on the study of the thermoelectric properties in GeSi alloys, as well as their application in stable power generating devices operating at temperatures up to 1025°C.
Abstract: Thermoelectric phenomena result from the diffusion of electrons and phonons along a temperature gradient in electrically conducting solids. These diffusion currents are determined by the concentration of these particles, and their interaction with each other as well as with impurities and defects. By using simple physical arguments, expressions are derived for the basic thermoelectric transport parameters. These are the electrical and thermal conductivities and the Seebeck coefficient. For application of thermoelectricity to power generation, it is desirable to maximize the electronic diffusion and to minimize the phonon diffusion. The physical and materials requirements to achieve these desired transport properties will also be discussed, and particular attention will be given to a review of experimental data and the theoretical interpretation of these data on thermal transport and phonon scattering mechanisms in alloy semiconductors at high temperatures. Emphasis will be placed on the study of the thermoelectric properties in GeSi alloys, as well as their application in stable power generating devices operating at temperatures up to 1025°C. For completeness, the paper will also include the status of compound tellurides and their alloys for use up to 500°C, and recent research on the thermoelectric properties of selected III–V compound alloys to be used in a segmented thermocouple arrangement with GeSi alloys for improved power generating efficiency.
216 citations
TL;DR: In this article, the effect of the hydrostatic pressure on the ionic and electronic conductivities of Ag 2 S as a mixed conductor is investigated and the model accounting for these data consistently is proposed.
Abstract: Ag 2 S is a mixed conductor in which electrons and Ag ions are mobile. (1) The electronic properties; the various properties such as the electronic conductivity, Hall coefficient, thermoelectric power, surface potential, magnetic susceptibility due to conduction electrons and infrared reflection etc. are measured as the electron concentration is varied with use of the galvanic cell Ag|AgI|specimen|Pt. The model accounting for these data consistently is proposed. (2) The ionic properties; the ionic conductivity and the thermal diffusion of Ag ions are measured with use of Ag|AgI probes. The L 2 -dependence of the time of polarization, where L is the length of the specimen, is checked. The effect of the hydrostatic pressure on the ionic and electronic conductivities are also measured. (3) Simple devices demonstrating the characteristics of Ag 2 S as a mixed conductor are described.
67 citations
TL;DR: In this paper, a small-polaron (hopping) model is presented for single crystals of Na0.33V2O5, and the Hall coefficient at 300°K is shown to correspond to n−type carriers at a density of 2.2 cm2V−·sec−1 and a Hall mobility of 0.050 eV.
Abstract: New data are presented for single crystals of Na0.33V2O5. Conductivity along the b axis follows a dependence of the form σT = A exp( − E / kT) with E = 0.067 eV below 140°K and E = 0.057 eV above 140°K. The Seebeck coefficient changes from − 225 μV deg−1 at 70°K to − 135 μV deg −1 at 150°K; thereafter, it remains constant to 300°K. The Hall coefficient at 300°K is − 3 × 10−3cc C−1 which corresponds to n‐type carriers at a density of 2.2 = 1021 cc−1 and a Hall mobility of 0.2 cm2V−·sec−1. At 189°K, the Hall data indicate identical carrier density but a mobility about half as large as at room temperature. All the above data together with reported magnetic susceptibility results can be fitted by a small‐polaron (hopping) model. Donor states are believed to be Γ6 levels of V4+. These are 0.016 eV below Γ7 conduction states between which hopping occurs with an activation energy of 0.050 eV. Detailed calculation shows a good fit with a crystal‐field model in which d1‐ion levels are split under tetragonal distortion Δ = 0.10 eV with spin‐orbit coupling constant λ = 0.02 eV, and delocalization parameter k = 1.0. Arguments are given for believing that the electrons responsible for the conduction and the observed paramagnetism hop from vanadium to vanadium and are not delocalized over the oxygen framework through V(3d) − O(pπ) overlap. There is, however, evidence for considerable covalent bonding of the σ type between the vanadium and oxygen atoms.
64 citations
TL;DR: In this article, the properties of amorphous Ge and Si are reviewed: short-range order, electrical conductivity, Hall effect, thermoelectric power, rectification and injection in junctions with single crystals, photoconductivity and non-ohmicity in high electric fields.
63 citations
TL;DR: In this paper, the electrical conductivity and Seebeck coefficient of polycrystalline NiO were measured as a function of temperature and of oxygen partial pressure over a large part of the phase field of stable NiO.
Abstract: The electrical conductivity and the Seebeck coefficient of single‐crystal and polycrystalline NiO were measured as a function of temperature and of oxygen partial pressure over a large part of the phase field of stable NiO. In the temperature range 1000°–1600°C the electrical conductivity was found to be proportional to the fourth root of the oxygen partial pressure. This pressure dependence is that which one would expect for pure, nonstoichiometric NiO containing singly ionized metal vacancies as the predominant point defects. The activation energy for conduction, ΔHc, computed from σ = σ0exp (−ΔHc / kT), was found to be 0.92 ± 0.02 eV. The Seebeck coefficient of NiO was found to be p type over the entire range of temperatures and oxygen partial pressures measured. From the temperature dependence of the Seebeck coefficient, the enthalpy of formation of defects in NiO was calculated to be 0.66 ± 0.03 eV. From the measured temperature dependence of the electrical conductivity and the Seebeck coefficient it...
60 citations
TL;DR: In this article, measurements of electrical conductivity and Seebeck coefficient have been made on p-type cuprous oxide single crystals in the temperature range from 300° to 500°K.
57 citations
TL;DR: In this paper, measurements of high-temperature Hall coefficient, electrical conductivity, and thermoelectric power in polycrystalline n-type samples of InAsxSb1−x alloys of extrinsic carrier concentration ~1017/cm3 were made.
Abstract: Measurements have been made of the high-temperature Hall coefficient, electrical conductivity, and thermoelectric power in polycrystalline n-type samples of InAsxSb1−x alloys of extrinsic carrier concentration ~1017/cm3. From the Hall-coefficient data, values of the extrapolated absolute-zero band gap E00 have been determined over the whole alloy range, the thermoelectric power results being used to provide a correction factor to allow for effects of degeneracy. In all cases this correction was found to be very small. The resultant values of E00 for the alloys are somewhat lower than those obtained previously from optical absorption data and show a minimum of 0.17 eV at x ~0.4. From the electrical conductivity data, values of electron mobility μc have been obtained as a function of temperature T and composition x. At all temperatures in the range 0–500 °C, μc is found to vary linearly with x, indicating that the effects of alloy scattering are negligible. For each value of x, μc is found to satisfy the re...
43 citations
TL;DR: In this article, the drift mobility of p-type CoO doped with Li has been analyzed in the temperature region 150°-1300°K and it is concluded that the large temperature dependence of the conductivity is almost completely determined by the change in the charge-carrier concentration.
43 citations
TL;DR: In this paper, a three-band model was used to investigate the Hall effect for single crystals of the Fe1−xCuxCr2S4 system and showed that substitution of Fe by Cu causes n-type conduction between x∼0.2 and x ∼ 0.5 in the temperature range 4.2°-550°K.
Abstract: Thermoelectric power α, electrical conductivity σ, and Hall effect have been studied for single crystals of the Fe1−xCuxCr2S4 system. While FeCr2S4 is a p‐type semiconductor, substitution of Fe by Cu causes n‐type conduction between x∼0.2 and x∼0.5 in the temperature range 4.2°–550°K. For x>0.5, p‐type conductivity is observed. An explanation of the experiments is given on the basis of a three‐band model.
40 citations
TL;DR: The thermoelectric power, S, of a number of palladium and platinum alloys has been measured in the temperature range 2°K to 120°K as discussed by the authors, and there is excellent numerical agreement between the observed values of Sd/T and those calculated by a method based on the rigid band model for all the platinum-gold alloys investigated.
Abstract: The thermoelectric power, S, of a number of palladium and platinum alloys has been measured in the temperature range 2°K to 120°K. For alloys of palladium or platinum with their neighbouring elements it has been possible to correlate the sign of the diffusion component of thermopower Sd in the residual resistance temperature range with the slope of the density of states versus concentration curves. Furthermore, there is excellent numerical agreement between the observed values of Sd/T and those calculated by a method based on the rigid band model for all the platinum-gold alloys investigated and for the palladium-silver alloys apart from one which contained less than 1 % silver. However, the sign of Sd was not predicted correctly for a palladium-platinum alloy. Each of the specimens exhibits a large positive phonon drag component of thermopower which persists to high temperatures and is not greatly reduced on alloying. These two features as well as the positive sign are the result of phonon-induc...
TL;DR: In this paper, a reversible temperature-dependent transformation to a disordered trigonal structure (space group P3ml) has been shown to occur for NiTi 2 S 4 and NiTi2 Se 4 at approximately 340°K, which is a result of the disordering of the vacancies in the structure.
TL;DR: In this article, a detailed comparison between the Ziman theory of electron transport and the experimental data is possible for this particular system because the three partial structure factors are reasonably well established, and the prominent features in the observed data can be readily understood in terms of the basic theory.
Abstract: The absolute thermoelectric power of the liquid system copper-tin has been investigated as a function of temperature and composition. A detailed comparison between the Ziman theory of electron transport and the experimental data is possible for this particular system because the three partial structure factors are reasonably well established. The comparison shows that the prominent features in the observed data can be readily understood in terms of the basic theory.
TL;DR: In this article, conductivity, Hall coefficient, and thermoelectric power data for reactively sputtered vanadium dioxide thin films both above and below the metal-semiconductor transition were investigated.
Abstract: Change‐transport phenomena in thin films of vanadium dioxide have been investigated. This paper presents conductivity, Hall coefficient, and thermoelectric power data for reactively sputtered vanadium dioxide thin films both above and below the metal‐semiconductor transition. Measurements were made both on single‐crystal films and highly oriented polycrystalline films. For temperatures below the transition, the data are interpreted in terms of a two‐band model of a semiconductor having a conduction band and an impurity band in which conduction takes place among interacting impurity levels.
TL;DR: In this article, the Hall coefficient, thermoelectric power and mobility for temperatures in the vicinity of 300°K were measured in semiconducting CdF 2, in which the electron polar optical phonon interaction does not appear to be the dominant scattering mechanism.
TL;DR: In this article, the conductivity and thermoelectric power of hafnium-doped yttrium iron garnets and a calcium vanadium bismuth iron garnet indicate that conduction should be described by localised rather than a band model.
TL;DR: In this paper, the superconductive critical temperature T c, the room-temperature magnetic susceptibility and thermoelectric power of several Cu 3 Au-type alloys have been measured.
TL;DR: The electrical resistivity, Hall coefficient, thermoelectric power, and magnetic susceptibility of polycrystalline samples of thorium tetraboride and thorium hexaboride have been measured over a range of temperatures as discussed by the authors.
Abstract: The electrical resistivity, Hall coefficient, thermoelectric power, and magnetic susceptibility of polycrystalline samples of thorium tetraboride and thorium hexaboride have been measured over a range of temperatures. Both compounds exhibit metallic properties. The carrier concentration, about 2 electrons per thorium atom, is that predicted by the bonding model of Lipscomb and Britten.
TL;DR: In this paper, the thermoelectric figures of merit of ternary chalcogenides A2IBIVX3, AIBVX2 and A3IBVX4 (AI=Cu; BIV=Ge, Sn; BV=Sb; X=S, Se, Te) were evaluated at room temperature.
Abstract: Electrical conductivity, Seebeck coefficient, thermal conductivity and microhardness of ternary chalcogenides A2IBIVX3, AIBVX2 and A3IBVX4 (AI=Cu; BIV=Ge, Sn; BV=Sb; X=S, Se, Te) were measured and their thermoelectric figures of merit are evaluated at room temperature. All of the compounds have positive Seebeck coefficients. The lattice thermal conductivity increases linearly with the increase of the microhardness for AIBVX2 and A3IBVX4s eries. The Keyes' relationship between lattice thermal conductivity and melting point are applicable for AIBVX2 and A3IBVX4 series. On the other hand, the lattice thermal conductivity of A2IBIVX3 series does not satisfy the usual relationships mentioned above. Values of zmax, the value of the thermoelectric figure of merit at the optimized carrier concentration estimated by the formulas based on the simplified assumptions are in the order of 10-5 deg-1., 10-4 deg-1. and 10-3 deg-1. for sulphides, selenides and tellurides, respectively. The value of zmax of Cu3SbTe4 is estimated to be 2.8×10-3 deg-1.
TL;DR: In this paper, room temperature measurements of the thermoelectric power α and Hall coefficient R have been made as a function of the magnetic field B on polycrystalline n-type samples of InAsxSb1−x, alloys of ca...
Abstract: Room-temperature measurements of the thermoelectric power α and Hall coefficient R have been made as a function of the magnetic field B on polycrystalline n-type samples of InAsxSb1−x, alloys of ca...
TL;DR: In this paper, the absolute Seebeck coefficient, electrical resistivity, and thermoelectric figure of merit have simultaneously measured on Bi 97 Sb 3 and Bi 90 Sb 10 alloy single crystals of various orientations between 77°K and 300°K.
Abstract: The absolute Seebeck coefficient, electrical resistivity, and thermoelectric figure of merit have simultaneously measured on Bi 97 Sb 3 and Bi 90 Sb 10 alloy single crystals of various orientations between 77°K and 300°K. Under the assumption of independent three valley bands for both the valence and conduction bands, the electronic thermal conductivities have been calculated. They are anisotropic and the larger values being those perpendicular to the trigonal axis. In the 3 at.% antimony alloy, the total thermal conductivities both parallel and perpendicular to the trigonal axis are practically constant ( K || =50±5 mW/cm·deg and K ⊥ =75±5 mW/cm·deg) between 77°K and 300°K. In the 10 at.% antimony alloy, each of them gradually increase with temperature. It seems that most of heat are transported by carriers in the studied temperature range in both alloys.
TL;DR: The thermoelectric power (TEP) of dilute copper alloys containing transition metals of the first great period have been measured with reference to pure copper in the temperature range from 4.2 to 273°K as discussed by the authors.
TL;DR: In this paper, the authors analyzed the electrical resistivity, Hall coefficient, and thermoelectric power of silver telluride over a large temperature range including both solid and liquid states.
Abstract: Measurements of the electrical resistivity, Hall coefficient, and thermoelectric power have been carried out for silver telluride over a large temperature range including both solid and liquid states. The analysis of the experimental data shows that in the solid state the transport properties are governed by an ambipolar process with an electron mobility much higher than the hole mobility (μn = 10 μp). It is found that the temperatur dependence of the electron mobility can be represented by a T−3-law. Deviations from the stoichimetric composition of Ag2Te have been studied. For all specimens, melting is accompanied by discontinuous variations in the transport propeties. Above the melting point, the magnitude of the measured parameters and their temperature dependence show that liquid silver telluride behaves as a semiconductor. The contribution of Ag+ ions to transport phenomena is suggested to account for the behaviour of the electrical properties. Experimental data have been analysed in terms of conventional theories.
TL;DR: In this article, a study of the electrical properties including resistivity, Hall effect, and thermoelectric power is made on slightly Li-doped single crystals of MnO.
Abstract: A study of the electrical properties including resistivity, Hall effect, and thermoelectric power is made on slightly Li-doped single crystals of MnO. The temperature dependence of the conductivity is almost completely determined by the charge carrier concentration. From the results of electrical conductivity and thermoelectric power measurements it is concluded that the samples are slightly compensated. When the samples are thermally treated in an atmosphere containing oxygen in excess compared to the equilibrium pressure, more donor centres are introduced resulting in further compensation. The height of the acceptor (Li+Mn+++) level is 0.64 eV while the band gap has a value of 2.6 eV. The calculations of the density of states Nv and the effective mass m* yield a high value. These results indicate that holes move in a narrow band.
TL;DR: In this paper, Nitrate anions and nitric acid molecules are intercalated to an approximate formula C24+NO3−3HNO3 for the first sequence and properties measured over a wide range of temperatures include thermal expansions, X-ray diffractions, electrical resistivities and thermoelectric power (TEP).
TL;DR: In this article, the influence of segregated tellurium phase, determined metallographically, on the thermoelectric figure of merit (Z), electrical conductivity (σ), Seebeck coefficient (α), and thermal conductivity was investigated.
Abstract: A study has been made in n‐type Bi2Te3+x, n‐type Bi2Se0.45Te3+x, and p‐type Bi0.5Sb1.5Te3+x of the influence of segregated tellurium phase, determined metallographically, on the thermoelectric figure of merit (Z), electrical conductivity (σ), Seebeck coefficient (α), and thermal conductivity (κ). It was found that Z and σ at a given α value were reduced by excessive amounts of the Te phase. Calculation using an idealized two‐phase model has shown that in this case circulating currents are unimportant. The effects appear to be due to a redistribution of electrical and thermal current by the Te phase located mostly between cleavage planes where any misalignment can have a strong influence. Zone melting of p‐type Bi0.5Sb1.5Te3.13 at low speeds of about 0.1 cm/h produced an increase in the average value of Z and a decrease in the amount of Te phase.
TL;DR: In this article, an exploratory investigation of thermoelectric power in three different specific situations was conducted to investigate the effect of extrinsic photoexcitation involving imperfection states in the crystal.
Abstract: Thermoelectric power measurements have seldom been used to investigate the photoelectronic properties of semiconductor crystals. This paper presents the results of an exploratory investigation of thermoelectric power in three different specific situations: (1) the effect on thermoelectric power of extrinsic photoexcitation involving imperfection states in the crystal, (2) the effect on thermoelectric power of optical quenching of photoconductivity, and (3) thermally stimulated thermoelectric power, associated with the emptying of electron and hole traps in the crystal. The increased sensitivity of the thermoelectric effect to two‐carrier phenomena as compared to the Hall effect, makes it a valuable effect for investigating the contribution of electrons and holes to photoelectronic behavior. The results obtained with single‐crystal CdS suggest that: (1) The thermoelectric effect is quite useful in imperfection‐level spectroscopy, (2) Sensitizing imperfections for photoconductivity have a complex dipole‐like structure, and (3) Holes play a larger role in photo‐electronic effects than commonly attributed. Further investigations of the techniques using thermoelectric power are certainly indicated.
TL;DR: In this paper, measurements of the thermoelectric power of gold + 0.03 atomic percent iron from 0.35°K - 10°K and 0.77 kOe are presented.