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P. V. Gorskyi

Publications and source records attributed to P. V. Gorskyi.

11 recordsLinked to original sources
arXiv2022

Do thermoelectric generator modules degrade due to nickel diffusion

The paper shows by calculation that the diffusion of nickel even for 50 years does not lead to degradation of thermoelectric generator modules. In the process, we used the theory of composites to calculate the electrical contact resistance, our own diffusion theory of electrical contact resistance, as well as the method for approximating the temperature dependences of thermoelectric material characteristics from the experimental data. When using the above method, it was assumed that the main mechanism of scattering of free charge carriers in a thermoelectric material is their scattering on the deformation potential of acoustic phonons with a free path length independent of energy but inversely proportional to temperature, and the main mechanism of phonon scattering is phonon-phonon scattering with Umklapp, which is not affected by the nickel impurity in the thermoelectric material. Thus, it was believed that the role of nickel is reduced only to a change in the concentration of free charge carriers in the material.

cond-mat.mtrl-sci↗
arXiv2022

ThermoEMF of powder-based thermoelectric materials

In the paper, the thermoEMF of powder-based thermoelectric materials (TEM) is calculated. The calculation is made on the assumption of power dependence of mean free path on energy. The thermoEMF decreases with increasing the average radius of powder particles, however, it drastically increases with an increase in power exponent in the law of dependence of the mean free path of relaxation time on energy (scattering index). Therefore, it turns out that the thermoEMF of powder-based TEM with a higher scattering index can be even greater than the thermoEMF of a single-crystal material with a low scattering index. As a consequence, a significant increase in the thermoEMF and, hence, in the thermoelectric figure of merit of TEM in going to powder materials, especially in the case of degenerate electron gas, can be expected only if dielectric or vacuum barriers between powder particles do not lead to a significant decrease in electrical conductivity. At the same time, tunnelling through the abovementioned barriers should provide such an energy filtration of charge carriers, which leads both to an increase in the proportion of "useful" charge carriers with energy greater than the chemical potential, and to an increase in the scattering index. However, experimentally, there is no significant increase in thermoEMF in going from single-crystal materials to powders, most likely because such energy filtering does not take place.

cond-mat.mes-hall↗
arXiv2018

Estimation of the electrical and thermal contact resistances and thermoemf of thermoelectric material-metal transient contact layer due to semiconductor surface rougness

The impact of semiconductor surface roughness on the electrical and thermal contact resistances and thermoEMF of thermoelectric material (TEM)-metal transient contact layer is studied theoretically. The distribution of hollows and humps on the rough surface is simulated by the truncated Gaussian distribution. The impact of distribution parameters on the electrical contact resistance and thermoEMF of thermoelectric material-metal contact is studied.

cond-mat.mes-hall↗
arXiv2015

Use of similatity criteria for evaluating the thermoelectric figure of merit of superlattices

In this paper, general relationships that allow evaluating the figure of merit of both two-dimensional superlattices and three-dimensional crystals with a quadratic and isotropic energy spectrum of free charge carriers are derived. It is shown that with the same values of the so-called dimensionless temperature and scattering coefficient, the figure of merit of superlattices is always lower than that of three-dimensional crystals. The figure of merit of superlattices can become higher that that of three-dimensional crystals if the dimensionless temperature of free charge carrier gas and (or) scattering coefficient in them is considerably higher than in three-dimensional crystals.

cond-mat.mes-hall↗
arXiv2015

On conditios of high figure of merit and methods of search for promising superlattice thermoelectric materials

This paper presents a rigorous calculation of the figure of merit of superlattice thermoelectric material (SL TEM) with regard to real three-dimensionality and nonparabolicity of its energy spectrum with the arbitrary level of openness of its Fermi surface (FS).It is shown that the figure of merit of SL TEM in the temperature range of 300-500K is drastically increased with increasing level of openness of FS. However, due to the presence of lattice component of thermal conductivity the figure of merit of SL TEM is rather responsive to the distance between the layers and drastically drops with its increase. Besides, for the same material, coefficient of performance of a refrigerator in the framework of its simplest model was calculated. It was established that if material band spectrum is described by the Fivaz model, the coefficient of performance is drastically increased with increasing the level of openness of FS and in case of transient FS it reaches 1.9 between the temperatures of 300 and 230K. However, as the distance between the layers of SL TEM increases 2 times, it drops to 0.4 Based on the obtained criteria, four methods of search for promising SL TEM with the use of quantizing magnetic fields are proposed.

cond-mat.mes-hall↗
arXiv2015

Gigantic negative magnetoresistance of nanoheterostructures described by the Fivaz model

It is shown that the negative magnetoresistance of nanoheterostructures described by the Fivaz model can become apparent not only under strong, but also under intermediate or weak degeneracy of free carrier gas in them. In so doing, in the Fivaz model it becomes apparent to a larger extent than in the case of a parabolic, though anisotropic, conduction band. The negative magnetoresistance can be both due to spin splitting and the Landau quantization proper.

cond-mat.mes-hall↗
arXiv2013

Longitudinal Seebeck coefficient of the charge ordered layered crystals in a strong quantizing magnetic field

The longitudinal Seebeck coefficient of the charge-ordered layered crystals in a strong quantizing magnetic field normal to layers plane has been determined. The conditions whereby charge ordering parameter and chemical potential are oscillating functions of magnetic field induction are considered. The longitudinal Seebeck coefficient has been calculated for two models of relaxation time:i)constant relaxation time and ii)relaxation time proportional to the longitudinal velocity. It has been shown that in a quasi-classical region of magnetic fields for the case of relaxation time proportional to the longitudinal velocity Seebeck coefficient is less than for the case of constant relaxation time. In this region for selected problem parameters it does not exceed 4.37mu\V/K.In the strong quantizing magnetic fields for both models of the relaxation time the longitudinal Seebeck coefficient is virtually the same. For selected problem parameters its maximal modulus is 2033\muV/K. At the same time, in the disordered layered crystals,in a quasi-classical region,the Seebeck coefficient is approximately one order of magnitude less than for the charge ordered crystals. In the strong magnetic fields,the Seebeck coefficient for the disordered layered crystals is factor of 7 or 9 less than for the charge ordered crystals. However,in super strong magnetic fields,under current carriers concentration in the only filled Landau sub-band,for both models of of the relaxation time the modulus of the Seebeck coefficient tends to zero according to asymptotic law α_{zz}\proptoB^{-2}.

cond-mat.mes-hall↗
arXiv2013

Power factor for layered thermoelectric materials with a closed Fermi surface in a quantizing magnetic field

The field dependence of power factor for a layered thermoelectric material with a closed Fermi surface in a quantizing magnetic field and at helium temperatures has been studied in the geometry where the temperature gradient and the magnetic field are perpendicular to the material lasyers. The calculations are carried out in the constant relaxation time approximation. In weak magnetic fields,the layered structure effects are shown to manifest themselves in a phase retardation of power factor oscillations,increase of their relativeb contribution, and certain reduction of the power factor in whole.In highmagnetic fields,there exists an optimal range,where the power factor reaches its maximum,with the corresponding value calculated for the chosen parameters of the problem in the effective mass approximation being by 12%higher than that for real layered crystals.Despite low temperatures,the power factor maximum obtained with those parameters in a magnetic field of 1T has a value characteristic of cuprate thermoelectric materials at 1000K. For this phenomenon to take place, it is necessary that the ratio between the free path of charge carriers and interlayer distance should be equal to or larger than 30000. However,in ultraquantum magnetic fields, the power factor drastically decreases following the dependence P propto T^-3B^-6.The main reason for this reduction is a squeeze of the Fermi surface along the magnetic field in the ultraquantum limit owing the condensation of charge carriers on the bottom of a single filled Landau subband.

cond-mat.mes-hall↗
arXiv2011

Can layered-structure effects be observed, if the Fermi surface is closed?

By analyzing the longitudinal conductivity in a quantizing magnetic field directed perpendicularly to the crystal lattice layers, it has been demonstrated that the layered-structure effects can be observed not only in crystals with highly open Fermi surfaces, as was conventionally believed earlier, but also in crystals with closed ones. The calculations were carried out in the constant-relaxation-time approximation. In weak magnetic fields, layered-structure effects manifest themselves as a phase retardation of Shubnikov--de Haas oscillations and a certain increase of the relative contribution made by the latter. In the range of high magnetic fields, there exists an optimal interval, in which the layered-structure effects reveal themselves in the form of a sharp non-monotonous dependence of conductivity on the magnetic field. In addition, it has been shown that the layered-structure effects result in a decrease of the proportionality factor between the magnetoresistance and the magnetic induction in the longitudinal Kapitsa effect. The longitudinal conductivity of layered crystals in ultra-quantum magnetic fields has also been analyzed. It is shown that the following dependences of the magnetoresistance on the magnetic field can be obtained, depending on the model used for the filling of the single Landau subband and on whether the longitudinal conductivity is considered to be of either the drift or diffusion type: $ρ_{zz}\propto TB^{2}$,\ $ρ_{zz}\propto B^{3}$, and $ρ_{zz}\propto B^{4}$.

cond-mat.mes-hall↗