Search

This study investigates a strong magnetic field acting over an elastic rotator semiconductor medium. The Thomson effect due to the magnetic field during the photothermal transport process is studied, and the thermoelectricity theory is used to explain the behavior of waves in the homogenous and isotropic medium under the effect of variable thermal conductivity. The variable thermal conductivity is considered as a linear function of the temperature. The two-dimensional deformation equations are used to describe the overlaps among plasma, electrical, thermal, and magneto-elastic waves. The charge density of inertia-particles is considered as a function of time for studying the induced electric current. The normal mode analysis is used to obtain the exact solutions of the physical field distributions as part of this phenomenon. To obtain the complete solutions of the physical field quantities, the certain mechanical loads, electromagnetic effects, thermal effects, and plasma recombination process are applied herein. The results of the physical distributions are graphically depicted and discussed in consideration of the internal heat source, rotation, and Peltier coefficient. [ABSTRACT FROM AUTHOR]

The analytical expressions derived using simple models provide clear insights on the processes in thermoelectric coolers. The model of constant transport coefficients (CTC) considers that the thermal conductivity, the electrical resistivity and the Thomson coefficient are constants. The version of the CTC model that has become standard in the description of the global energy balance may yield grossly inaccurate predictions for thermoelectric cooling applications. We show that these failures can be avoided by accurately describing the Thomson effect in the energy balance. Calculations for bismuth telluride semiconductors show that deviations as large as a factor of three in the Thomson power contribution to the global balance may be found under conditions of practical interest. Compared to the standard version (valid only for moderate temperature gradients), the improved version (valid for highly nonlinear temperature distributions) of the CTC model predicts that a larger fraction of the power released by the electric current leaves the thermoelectric element through the hot boundary. Significant differences in the estimations of the cooling capacity and the coefficient of performance of the thermoelectric cooler are also observed. [ABSTRACT FROM AUTHOR]

We present a simplified, rapid, and accurate method for the measurement of the thermoelectric Thomson coefficient by the dynamical heating of a suspended wire by an alternating current. By applying a temperature gradient across the wire, we find that the response at the second harmonic of the excitation frequency is directly proportional to the Thomson coefficient. The absolute thermoelectric coefficient of a single material can therefore be extracted with high precision by using a phase sensitive detector. We test our method on platinum and nickel wires and develop both analytical and numerical models to determine the leading sources of error. [ABSTRACT FROM AUTHOR]

This paper studies one of the magnetic analogs of well-known thermoelectric effects, the spin Thomson effect. This effect consists in the existence of a heat flux caused by the spin current and is described by a modified heat equation. When comparing the published experimental data and the theoretical model, it was possible to find the Thomson spin coefficient for iron-yttrium garnet. From a viewpoint of thermal conductivity, the presence of a magnetic field of 1750 Oe turns out to be equivalent to the motion of the medium at a rate of 6.5 mm/s and leads to the existence of a giant heat flux of 18.9 kW/m2 due to the transfer of heat by spins. The ability to control heat fluxes by means of a magnetic field allows the use of materials based on iron-yttrium garnet for practical applications as thermal switches for solid-state cooling. [ABSTRACT FROM AUTHOR]

A comprehensive study of the mechanisms of heating and cooling originating from an electrical current in semiconductor devices is reported. The variation in temperature associated with the Peltier effect is not related to the presence of heat sources and sinks if the heat flux is correctly determined. The Thomson effect is commonly regarded as a heat source/sink proportional to the Thomson coefficient, which is added to the Joule heating. In the present work, we will show that this formulation of the Thomson effect is not sufficiently clear. When the heat flux is correctly defined, the Thomson heat source/sink is proportional to the Seebeck coefficient. In the conditions in which the Peltier effect takes place, the temperature gradient is created, and, consequently, the Thomson effect will occur naturally. [ABSTRACT FROM AUTHOR]

The semi-analytical methods of thermoelectric energy conversion efficiency calculation based on the cumulative properties approach and reduced variables approach are compared for 21 high performance thermoelectric materials. Both approaches account for the temperature dependence of the material properties as well as the Thomson effect, thus the predicted conversion efficiencies are generally lower than that based on the conventional thermoelectric figure of merit ZT for nearly all of the materials evaluated. The two methods also predict material energy conversion efficiencies that are in very good agreement which each other, even for large temperature differences (average percent difference of 4% with maximum observed deviation of 11%). The tradeoff between obtaining a reliable assessment of a material’s potential for thermoelectric applications and the complexity of implementation of the three models, as well as the advantages of using more accurate modeling approaches in evaluating new thermoelectric materials, are highlighted. [ABSTRACT FROM AUTHOR]

In this work, the influences of the Thomson effect and the geometry of the p-type segmented leg on the performance of a segmented thermoelectric microcooler (STEMC) were examined. The effects of geometry and the material configuration of the p-type segmented leg on the cooling power (Qc) and coefficient of performance (COP) were investigated. The influence of the cross-sectional area ratio of the two joined segments on the device performance was also evaluated. We analyzed a one-dimensional p-type segmented leg model composed of two different semiconductor materials, Bi2Te3 and (Bi0.5Sb0.5)2Te3. Considering the three most common p-type leg geometries, we studied both single-material systems (using the same material for both segments) and segmented systems (using different materials for each segment). The COP, Qc and temperature profile were evaluated for each of the modeled geometric configurations under a fixed temperature gradient of ΔT = 30 K. The performances of the STEMC were evaluated using two models, namely the constant-properties material (CPM) and temperature-dependent properties material (TDPM) models, considering the thermal conductivity (κ(T)), electrical conductivity (σ(T)) and Seebeck coefficient (α(T)). We considered the influence of the Thomson effect on COP and Qc using the TDPM model. The results revealed the optimal material configurations for use in each segment of the p-type leg. According to the proposed geometric models, the optimal leg geometry and electrical current for maximum performance were determined. After consideration of the Thomson effect, the STEMC system was found to deliver a maximum cooling power that was 5.10% higher than that of the single-material system. The results showed that the inverse system (where the material with a higher Seebeck coefficient is used for the first segment) delivered a higher performance than the direct system, with improvements in the COP and Qc of 6.67% and 29.25%, respectively. Finally, analysis of the relationship between the areas of the STEMC segments demonstrated that increasing the cross-sectional area in the second segment led to improvements in the COP and Qc of 16.67% and 8.03%, respectively. [ABSTRACT FROM AUTHOR]

Thermoelectric effects are envisioned to reduce programming currents in nanopillar phase-change memory (PCM) cells. However, due to the inherent symmetry in such a structure, the contribution due to thermoelectric effects on programming currents is minimal. In this paper, we propose a hybrid PCM structure, which incorporates a twofold asymmetry specifically aimed to favorably enhance the thermoelectric effects. The first asymmetry is introduced via an interface layer of low thermal conductivity and high negative Seebeck coefficient, such as polycrystalline SiGe, between the bottom electrode contact and the active region comprising the phase-change material. This results in an enhanced Peltier heating of the active material. The second one is introduced structurally via a taper that results in an angle-dependent Thomson heating within the active region. Various device geometries are analyzed using 2-D-axis-symmetric simulations to predict the effect on programming currents as well as for different thicknesses of the interface layer. A programming current reduction of up to 60% is predicted for specific cell geometries. Remarkably, we find that due to an interplay of Thomson cooling in the electrode and the asymmetric heating profile inside the active region, the predicted programming current reduction is resilient to fabrication variability. [ABSTRACT FROM PUBLISHER]

We present a study of a thermal biosensor based on bismuth nanowire that is fabricated for the detection of the human stress hormone cortisol using the Thomson effect. The Bi nanowire was grown using the On-Film Formation of Nanowires (OFF-ON) method. The thermal device was fabricated using photolithography, and the sensing area was modified with immobilized anti-cortisol antibodies conjugated with protein G for the detection of cortisol. The voltages were measured with two probe tips during surface modification to investigate the biochemical reactions in the fabricated thermal biosensor. The Bi nanowire-based thermal biosensor exhibited low detection limit and good selectivity for the detection of cortisol. [ABSTRACT FROM AUTHOR]

Thermoelectric (TE) materials play an important role in energy production and utilization, but the temperature dependence of material properties makes theoretical analysis challenging. In this work, the TE differential equation is solved by introducing the volume average of TE material parameters, and a simplified TE element model is established for a TE element with a linear temperature profile. The temperature dependence of the Seebeck coefficient, electrical resistivity and thermal conductivity are incorporated into the thermal conductivity equation, and the TE conversion efficiency is solved. This proposed model is applied to a high-performance N-type half-Heusler alloy, and the obtained maximum conversion efficiency agrees well with the numerical results (with relative error 1.36%) for an average temperature T m = 510 K and temperature difference Δ T = 440 K. The results confirm that the proposed model, which incorporates the Thomson effect, is simple and accurate, providing valuable guidance for optimal performance design of TE devices. • Putting volume average properties makes TE non-linear model to a linear one. • Conversion efficiency of the proposed model agrees well with the numerical result. • The effect of coefficients on η demonstrates the accuracy of the proposed model. [ABSTRACT FROM AUTHOR]