Thermoelectric Power Coefficient Research Articles

Thermoelectric power in low-density interstitial-free iron-aluminium alloys

Thermoelectric power (TEP) studies on low-density interstitial-free iron-aluminium alloys reveal that the TEP decreases with increase in the aluminium content on account of the introduction of lattice dispersion centres. The TEP coefficients, determined from the Nordheim-Gorter law, for 6.8 and 8.1 wt.% aluminium additions to α-iron are found to be higher than values reported in previous literature for small aluminium additions. The grain size has a very weak effect on the TEP of these alloys.

Hidden Fermi Liquid, Scattering Rate Saturation, and Nernst Effect: A Dynamical Mean-Field Theory Perspective

We investigate the transport properties of a correlated metal within dynamical mean-field theory. Canonical Fermi liquid behavior emerges only below a very low temperature scale T(FL). Surprisingly the quasiparticle scattering rate follows a quadratic temperature dependence up to much higher temperatures and crosses over to saturated behavior around a temperature scale T(sat). We identify these quasiparticles as constituents of the hidden Fermi liquid. The non-Fermi-liquid transport above T(FL), in particular the linear-in-T resistivity, is shown to be a result of a strongly temperature dependent band dispersion. We derive simple expressions for the resistivity, Hall angle, thermoelectric power and Nernst coefficient in terms of a temperature dependent renormalized band structure and the quasiparticle scattering rate. We discuss possible tests of the dynamical mean-field theory picture of transport using ac measurements.

Anomalous Nernst effect in the ferromagnetic Kondo lattice Ce3RhSi3

The ferromagnetic heavy fermion compound Ce3RhSi3 was studied by means of electrical resistivity, Hall effect, thermoelectric power and Nernst coefficient measurements. Below T ≈ 30 K, all the transport characteristics were found to behave anomalously as functions of temperature and magnetic field. In particular, the Hall and Nernst coefficients at low temperatures exhibit pronounced and strongly field-dependent maxima, likely possessing the same microscopic origin, which however cannot be captured by available theoretical models.

Thermal-physical and thermoelectric properties of solids near the polymorphic and superconducting transitions

The relationships are presented for the effective thermal conductivity and thermoelectric power coefficients near the superconducting and polymorphic phase transitions. The relationships are verified using the experimental data obtained for porous media saturated with a fluid. The experimental data obtained for the high-temperature superconductor YBa2Cu3Ox (x = 6.8, 6.9) and n-InAs are analyzed.

Evaluation of the intergranular corrosion susceptibility of UNS S31803 duplex stainless steel with thermoelectric power measurements

In this study, the use of thermoelectric power (TEP) measurements as a nondestructive method for the determination of the degree of sensitization (DOS) in UNS S31803 duplex stainless steel (DSS) is presented. Samples were aged for times up to 240h and subjected to the double loop electrochemical potentiokinetic reactivation (DL-EPR) test to calculate the DOS induced. The correlation between TEP and the DOS evaluated by the DL-EPR method indicates that the TEP coefficient is sensitive to gradual microstructural changes produced by thermal aging and may be used to monitor the susceptibility to intergranular corrosion in UNS S31803 DSS.

Microstructure and electrical properties of SnS thin films

Thin SnS films are of interest for optoelectronics. The influence of the preparation modes on the microstructure and electrical properties of thin SnS films obtained by the hot-wall method on substrates made of pure glass and glass with a molybdenum sublayer has been investigated. It has been established that the formation of SnS films with two texture types (111) and (010) is possible on the substrates made of pure glass, depending on the mode. The resistivity and the temperature coefficient of thermoelectric power of the SnS films on glass vary in the range from 12 to 817 Ω cm and from 37 to 597 μV/K, respectively, depending on the preparation modes. The activation energy is 0.11–0.12 eV.

Phase transitions and transport properties of Cu3Co0.5Se2 crystals

We have synthesized a solid solution with the composition Cu3Co0.5Se2 and investigated its structural phase transitions by high-temperature X-ray diffraction on a D8 Advance diffractometer. The results demonstrate that, in the range 100–773 K, the solid solution undergoes two phase transitions: at 560 K, the low-temperature, orthorhombic phase (α) transforms into an intermediate, primitive cubic phase (β); at 765 K, the β-phase transforms into a high-temperature phase (γ, sp. gr. Fm3m). The thermoelectric power, electrical conductivity, and Hall coefficient of the solid solution were measured in the temperature range 80–350 K. The observed temperature variation of its thermoelectric power and conductivity can be accounted for under the assumption that its conduction band has an additional subband due to the cobalt atoms.

(Invited) Transport Properties of Mixed Ionic Electronic Conductors under Thermodynamically Equilibrated Conditions: Measurements on Porous Bodies

Electrical conductivity, thermoelectric power, and surface exchange coefficient were measured on porous oxide samples. The rationale for using porous instead of dense samples was that porous samples equilibrate with the imposed atmosphere much faster compared to dense samples due to rapid gas phase transport through pores and rapid solid state transport into micron sized particles of porous samples. Experiments were conducted on Gd2O3-doped CeO2 (GDC), Sm2O3-doped CeO2 (SDC), K and Y doped BaZrO3, and Sr-doped LaCoO3 (LSC). Thermoelectric power was also measured on silver for comparison. Chemical diffusion coefficient of oxygen was measured by conductivity relaxation on a dense sample with porous surface layers. The results showed that in all cases, the use of porous samples, or dense samples with porous surface layers, facilitated rapid equilibration and allowed the measurement of properties under thermodynamically equilibrated conditions.

Earth-abundant non-toxic Cu2ZnSnS4 thin films by direct liquid coating from metal–thiourea precursor solution

A simple process for deposition of pure CZTS films from a methanolic solution of metal–thiourea complex is described. The precursor films are thermolysed at 200°C in air for 10min. Formation of kesterite CZTS is confirmed by X-ray diffraction (XRD). The films have grains of 100–200nm and rms roughness of 1–2nm. The energy band gap of CZTS films is 1.4eV and is p-type in nature with electrical conductivity of 0.5S/cm and thermo electric power coefficient of 86μV/K. The films are photoconducting.

Electrical conductivity of cobalt–titanium substituted SrCaM hexaferrites

A series of polycrystalline M-type hexagonal ferrites with the composition Sr0.5Ca0.5CoxTixFe12−2xO19 (where x=0.0–0.8) were prepared by the conventional ceramic technique. The electrical conductivity has been measured from 300 to 590K. The dc conductivity, σdc, exhibited a semiconductor behavior. The negative sign of thermoelectric power coefficient S reveals that all samples are n-type semiconductors. Both σdc and mobility, μd, increases with the substitution of Co2+ and Ti4+ ions, reach maximum at x=0.4 and start decreasing at x>0.4. Many conduction mechanisms were discussed to explain the electric conduction in the system. It was found that the hopping conduction is the predominant conduction mechanism. For samples with compositional parameter x=0.0 and 0.8, the band conduction mechanism shares in electric conduction beside the hopping process.

Antiferromagnetic order and consequences on the transport properties of Ba4Ru3O10

Barium ruthenate Ba$_{4}$Ru$_{3}$O$_{10}$, in which Ru$_{3}$O$_{12}$ trimers are connected together to form a chequered two-dimensional framework, has been synthesised and its structural, magnetic and transport properties studied between 300 K and 2 K. The paramagnetic to antiferromagnetic transition at $T_N \sim 105$ K evidenced on the susceptibility curve coincides with an increase of electron localization in transport measurements. Thermoelectric power and Hall coefficient measurements both exhibit dramatic changes at $T_N$, characteristic of a reconstruction of the bands structure near the Fermi level. No pronounced structural changes are observed at TN in this compound. The magnetic scattering signal on the neutron powder diffraction patterns below $T_N$ is weak, but can be tentatively modelled with an antiferromagnetic ordering of the spins at both ends of a trimer, the spin of the more symmetric Ru site remaining idle. Crystal field and strong spin-orbit coupling at the Ru$^{4+}$ site seem to be the key parameters to understand the magnetic state of Ba$_{4}$Ru$_{3}$O$_{10}$.

Nondestructive assessing of the aging effects in 2205 duplex stainless steel using thermoelectric power

The microstructural transformation of ferrite into secondary austenite and sigma phase during long term exposure to high-temperatures (650–900 °C) in a 2205 duplex stainless steel has been investigated using the thermoelectric power (TEP) technique, scanning electron microscopy (SEM), Charpy-impact test (CIT), equivalent ferrite and sigma phases content measurements. The possibility of using the TEP coefficient as a nondestructive assessment technique to characterize the aging kinetics of 2205 duplex stainless steel is discussed. Experimental results indicate that TEP coefficient is sensitive to the gradual microstructural transformation of ferrite phase experienced by the 2205 duplex stainless steel during the aging treatments.

A comparative study of nanocrystalline Cu film deposited using anodic vacuum arc and dc magnetron sputtering

A comparative study of structural, electrical and thermoelectric properties of nanocrystalline copper thin films deposited using anodic vacuum arc plasma deposition technique and dc-magnetron sputtering is presented. The crystallographic texture and structural evolution of these films are investigated as a function of thickness within a range of 30 to 230nm using XRD and SEM. AVA deposited Cu films possess smaller grains with a lesser degree of crystallinity than dc-sputtered ones. Electrical resistivity, temperature coefficient of resistance and thermoelectric power of both as-deposited and annealed Cu films of AVA and dc-magnetron sputtering is measured and their dependence on the film thickness is investigated. AVA deposited Cu films having thickness less than 100nm show much higher resistivity than dc-sputtered ones. AVA deposited Cu films possess lower temperature coefficient of resistance values than dc-sputtered ones. The observed thickness dependence of thermoelectric power is larger in AVA deposited Cu films than in dc-sputtered ones. These electrical measurements reveal that AVA deposited Cu films possess more vacancies than dc-sputtered ones.

Dramatic effect of rare earth ion on the electrical and magnetic properties of W-type barium hexaferrites

A series of W-type hexaferrite samples with composition Ba 1− y La y Zn 0.5Mg 0.5CoFe 16O 27; 0≤ y≤0.07 were prepared using the solid state reaction to investigate their magnetic properties, AC and DC electrical conductivity and thermoelectric power as a function of composition and temperature. The X-ray diffraction was studied to identify the formation of the sample properly. Increasing of (a) and decreasing of (c) lattice parameters leads to a constant volume. The data of ac conductivity showed an increase with both temperature and frequency, and it becomes slightly independent of frequency at higher temperature, also the conduction mechanism depends on an La concentration. The results of the charge carrier mobility suggested that the hopping conduction mechanism of holes due to replacement of La 3+ rare earth ions on the expense of Ba 2+ ions is the predominant one. The transition temperature decreases with increasing La content. The values of dc electrical conductivity σ dc at room temperature ranged 4.85×10 −6–3.82×10 −6 (Ω −1 cm −1) and the values of the calculated activation energies E dc ranged 0.215–0.137 eV. The highest values of dielectric constant, electrical conductivity and Curie temperature, also the smallest value of porosity and effective magnetic moment are found at y=0.05. The thermoelectric power coefficient showed that the majority of charge carriers are P-type, except at y=0.03, 0.04 and 0.05 negative charge carriers (electrons) takes place at high temperature region.

Electronic transport and specific heat of

The results of low temperature thermoelectric power and the specific heat of 1T-VSe2 (Vanadium diselenide) have been reported along with the electrical resistivity, and Hall coefficient of the compound. The Charge Density Wave (CDW) transition is observed near 110K temperature in all these properties. The Thermoelectric power has been measured from 15K to 300K spanning the incommensurate and commensurate CDW regions. We observed a weak anomaly at the CDW transition for the first time in the specific heat of VSe2. The linear temperature dependence of resistivity and thermoelectric power at higher temperatures suggests a normal metallic behavior and electron-phonon scattering above the CDW transition. The positive thermoelectric power and negative Hall coefficient along with strongly temperature dependent behavior in the CDW phase suggest a mixed conduction related to the strongly hybridized s-p-d bands in this compound.

The impurities of iron and cobalt in mercury selenide: Localization effects of hybridized electronic states in the temperature dependences of thermoelectric power

The temperature dependences of thermoelectric power coefficient have been studied in mercury selenide with small concentrations of iron and cobalt impurities at low temperatures. The considerable anomalies (sharp non-monotonic regions of the temperature dependences), related to the influence of the impurities, have been revealed. On the base of the comparison with the data of the other experiments, obtained before, and interpretation of the anomalies, proposed by us, it has been shown that in crystals with iron impurities the specific behaviors above are explained by manifesting the hybridized electronic states on donor impurities. As a result of discussing the data, obtained on the crystal with cobalt impurities, it was established that the revealed anomalies of thermoelectric power are the conclusive evidences of hybridizing the states on donor cobalt impurities.

Thermoelectric Power Factor for Polyaniline/Molybdenum Trioxide Composites

The results of thermoelectric power (TEP), power factor and Seebeck coefficient of conducting polyaniline molybdenum trioxide (PANI/MoO 3 ) composites of different weight percentages (10, 20, 30, 40 and 50wt %) has been reported. The results are supported by the theory of coupled transport equations of heat and electricity in metals. It is observed that even though the Seebeck coefficient decreases with doping, the power factor increases with increase in electrical conductivity. The conductivity results lie between 10 – 5 and 10 – 3 S/cm from 0 wt% to 50wt% of MoO3 in PANI respectively match with that of conventional semiconductors.

Characterization of Weldments and Materials Using Thermoelectric Power Measurements

Thermoelectric power coefficient measurement techniques have been developed for numerous applications to guarantee material integrity by providing a non-destructive electronic property correlation to material microstructure, phase stability, specific solute additions, and lattice strain. How the electron concentration, the effective mass, and the dominating scattering mechanisms allow for non-destructive evaluation of materials will be described. Because thermoelectric power (TEP) is dependent upon numerous variables, additional non-destructive techniques are necessary to further characterize or classify the material or weldment. The concept of an electronic metallography laboratory is developed using additional collaborative NDE technologies.

Nondestructive characterization of the level of plastic deformation by thermoelectric power measurements in cold-rolled Ti–6Al–4V samples

This paper presents experimental data that illustrates the intrinsic sensitivity of the thermoelectric contact technique based on the Seebeck effect, in order to detect the presence of anisotropy due to plastic deformation produced by the manufacturing process of cold working at different degrees of reduction in thickness, namely 40, 60 and 80% in Ti–6Al–4V. In addition to the morphological anisotropy, the Ti–6Al–4V alloy also exhibits a substantial thermoelectric anisotropy due to the preferred alignment of the predominantly hexagonal grain structure. The results describe the behaviour of the thermoelectric power (TEP) coefficient with respect to the anisotropy and microstructure in a highly textured material, that presents both morphological and crystallographic texture. Ultrasonic measurements of shear wave velocity were also conducted in order to obtain a direct correlation between the presence of a significant anisotropy in the cold-rolled Ti–6Al–4V samples and the TEP measurements, before and after heat treatment (annealing). TEP measurements offer a means to assess the evolution of the level of plastic deformation, which allows for a better correlation between texture-induced anisotropy and the material's microstructural and properties. Of course, the TEP values depend on the physical nature and degree of the imperfection that is to be characterized.

α → β phase transition of Ag2Te in the AgSbTe2 alloy of the Ag-Sb-Te system

The effect of the Ag2Te phase on the electrical conductivity, thermoelectric power, and Hall coefficient of the AgSbTe2 alloy in the Ag-Sb-Te system has been studied at temperatures from 300 to 480 K. The results indicate that the phase transition of AgSbTe2 is broadened by ∼70% and is due to the α → β phase transition of Ag2Te.