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In southern countries, including European states, solar collectors for additional water-heating systems are widely used. However, the disadvantage of such systems is that a considerable proportion of solar energy cannot be used with increasing water temperature and dissipates into the environment. It is proposed to use waste heat at a high temperature, which is supplied to a thermoelectric generator (TEG) operating on the basis of a temperature difference between the hot water in the solar collector and cold water supplied to a radiator on the other TEG side. This is a new application of thermoelectric converters, in which the converter can act not only as a source of electrical energy but also as a source of low-potential heat coming from the radiator. The total conversion efficiency in such devices can reach 90%. It is shown that the use of p-type legs in a TEG with the cleavage planes of the legs parallel to the heat-flux direction instead of the conventional parallel orientation results in an increase in the thermoelectric efficiency by 25% on average in the temperature range of 100–300°C. [ABSTRACT FROM AUTHOR]

The possibility of fabricating thermoelectric coolers for operating temperatures below 90 K is considered. It is impossible to use the standard thermoelectric-cell scheme consisting of two semiconductor legs of n-type and p-type conductivity connected into an in-series electrical circuit for these temperatures. There is only one effective n-type thermoelectric material based on Bi–Sb solid solutions for the region of cryogenic temperatures. For this case, thermoelectric cells with a thermoelectric n-type leg and passive leg based on a high-temperature superconductor (HTSC) are investigated. The design of a thermoelectric cooler (module) consisting of thermoelectric n-type legs (extruded Bi0.91Sb0.09 crystals) and passive HTSC-based legs (YBa2Cu3O7 –x) is proposed. A magnetic field is used to increase the thermoelectric figure of merit ZT of the module. The maximal temperature drop between the hot and cold sides ΔT > 13.5 K and maximal cooling capacity Qc > 0.36 W are attained for the cryogenic module at a hot side temperature of Th = 80 K, current consumption of I = 6.4 A, and voltage of U = 0.10 V. [ABSTRACT FROM AUTHOR]

Extrusion methods have become widespread in the fabrication technology of thermoelectric materials with high strength characteristics. The extrusion method of thermoelectric materials based on Bi–Sb single crystals in a liquid medium under a high hydrostatic pressure is considered. It is shown that the proposed extrusion method makes it possible to fabricate Bi–Sb crystals of n-type conductivity with high thermoelectric characteristics at temperatures T ≲ 180 K. [ABSTRACT FROM AUTHOR]

In the last two decades, attention to alternative energy has grown dramatically. Thermoelectric energy conversion of heat from combustion systems and hot engines into electricity can be utilized for such purposes. Practical thermoelectric materials for such applications must exhibit both favorable thermoelectric and mechanical properties. BiTe-based alloys are known to be the best thermoelectric materials near room temperature. The current manuscript is concerned with the mechanical and transport properties of bulk submicro- and microstructured p-type BiSbTe samples with carrier concentration of ~1 × 10 cm to 3 × 10 cm. Among the investigated samples, the maximal ZT values of the microstructured BiSbTe were found to be higher (~0.96) compared with the submicrostructured samples (~0.81), due to the highly anisotropic nature of the investigated microstructured alloy. Nevertheless, microhardness values were found to increase with reduction of grain size (85 Hv to 145 Hv for the submicrostructured, compared with ~60 Hv for the microstructured samples). [ABSTRACT FROM AUTHOR]

It is shown that the microstructure and features of formation of surface states in nanocrystalline and polycrystalline PbTe:In films most significantly affect the character of photoconductivity in the spectral range of 1-2.5 THz. We present the results of a study and comparative analysis of the character of conductivity of PbTe:In films in the temperature range from 4.2 to 300 K in a static mode and in variable electric fields with a frequency of up to 1 MHz with illumination with white light and under the effect of high-power terahertz laser pulses with a wavelength of up to 280 μm. [ABSTRACT FROM AUTHOR]

The search for alternative energy sources is presently at the forefront of␣applied research. In this context, thermoelectricity for direct energy conversion from thermal to electrical energy plays an important role. This␣paper is␣concerned with the development of highly efficient p-type [(PbTe)(SnTe)(Bi2Te3)] x(GeTe)1− x alloys for thermoelectric applications using spark plasma sintering (SPS). Varying the carrier concentration of GeTe was achieved by alloying of PbTe, SnTe, and/or Bi2Te3. The rhombohedral to cubic phase transition temperature, Tc, was found to be sensitive to the degree of alloying. Highest power factor values ( P ≤ 33 μW/cm K2) were obtained for (GeTe)0.95(Bi2Te3)0.05 composition. [ABSTRACT FROM AUTHOR]

Temperature and frequency dependences of components of complex impedance for nanocrystalline PbTe:In films in the temperature range of 4.2–300 K and the frequency range from 20 Hz to 1 MHz have been studied. The films were deposited onto a cooled glass substrate and then annealed in an oxygen atmosphere at temperatures of 300 and 350°C. The charge-carrier transport in the studied films is controlled by charge transport over inversion channels at the surface of grains and by transitions through barriers at the grain boundaries. Parameters (resistance and capacitance) corresponding to each of above-mentioned mechanisms were determined. Dominant contribution to conductance of the film annealed at 350°C is made by inversion channels. It is shown that the transport of charge carriers over inversion channels in the region of low temperatures is realized by hopping conductivity. [ABSTRACT FROM AUTHOR]

Persistent IR photoconductivity in InAs/GaAs structures with layers of QDs with a p-and n-type conductivity was studied. At the initial stage, after the illumination is switched off, the relaxation of photoconductivity follows a logarithmic law. The relaxation time depends on temperature; it decreases as temperature increases. A simple model of photoconductivity relaxation, based on thermal activation of carriers from the QD layer, is proposed. The model is consistent with the experimental data. [ABSTRACT FROM AUTHOR]

The conductivity and the Hall coefficient of nanostructured TiN films synthesized by nonreactive RF magnetron sputtering have been experimentally studied. The mechanism of conductivity and the role of grain size are discussed. © 2004 MAIK “Nauka / Interperiodica”. [ABSTRACT FROM AUTHOR]