Structural properties of the AgSbTe 2 -AgSbSe 2 pseudobinary system were examined using thermal analysis, scanning electron microscopy, and x-ray powder diffractometry. It was found that partial substitution of Te by Se atoms leads to stabilization of the cubic crystal structure of alloys. The electronic-transport properties of materials were measured in order to investigate carrier conduction, band-gap features, and thermoelectric properties. The undoped homogeneous solid solution exhibits extremely low thermal conductivity of 0.5 W m −1 K −1 , a very large positive Seebeck coefficient of about 400-600 V K −1 at room temperature, low carrier densities of 10 16 -10 18 cm −3 , and thermally activated conduction. The influence of alloying on thermal-conductivity mechanisms and electron properties was discussed. The highest experimental dimensionless figure of merit ZT of the undoped AgSbSe 0.25 Te 1.75 sample is about 0.65 at a temperature of 520 K. The influence of doping on enhancement of thermoelectric properties of these materials was analyzed and optimal values of transport parameters were estimated.

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A series of samples with nominal compositions of AgSb 1Àx Sn x Se 2 (with x = 0.0, 0.1, 0.2, and 0.3) and AgSbSe 2Ày Te y (with y = 0.0, 0.25, 0.5, 0.75, and 1.0) were prepared. The crystal structure of both single crystals and polycrystalline samples was analyzed using x-ray and neutron diffractometry. The electrical conductivity, thermal conductivity, and Seebeck coefficient were measured within the temperature range from 300 K to 700 K. In contrast to intrinsic AgSbSe 2 , samples doped with Sn and Te exhibit apparent semiconducting properties (E g = 0.3 eV to 0.5 eV), lower electrical conductivity, and higher values of the Seebeck coefficient for a small amount of Sn (x = 0.1). Further doping leads to decrease of the thermoelectric power and increase of the electrical conductivity. In order to explain electron transport behavior observed in pure and doped AgSbSe 2 , electronic structure calculations were performed by the Korringa-Kohn-Rostoker method with coherent potential approximation (KKR-CPA).

Antimony telluride (Sb 2 Te 3 ) is an intermetallic compound crystallizing in a hexagonal lattice with R-3m space group. It creates a c lose packed structure of an ABCABC type. As intrinsic semiconductor characterized by excellent electrical properties, Sb 2 Te 3 is widely used as a low-temperature thermoelectric material. At the same time, due to unusual properties (strictly connected with the structure), antimony telluride exhibits nonlinear optical properties, including saturable absorption. Nanostructurization, elemental doping and possibilities of synthesis Sb 2 Te 3 in various forms (polycrystalline, single crystal or thin film) are the most promising methods for improving thermoelectric properties of Sb 2 Te 3 .Applications of Sb 2 Te 3 in optical devices (e.g. nonlinear modulator, in particular saturable absorbers for ultrafast lasers) are also interesting. The antimony telluride in form of bulk polycrystals and layers for thermoelectric and optoelectronic applications respectively were used. For optical applications thin layers of the material were formed and studied. Synthesis and structural characterization of Sb 2 Te 3 were also presented here. The anisotropy (packed structure) and its influence on thermoelectric properties have been performed. Furthermore, preparation and characterization of Sb 2 Te 3 thin films for optical uses have been also made.

The main aim of this work was to construct and test an apparatus for characterization of high temperature thermoelectric modules to be used in thermoelectric generator (TEGs) applications. The idea of this apparatus is based on very precise measurements of heat fluxes passing through the thermoelectric (TE) module, at both its hot and cold sides. The electrical properties of the module, under different temperature and load conditions, were used to estimate efficiency of energy conversion based on electrical and thermal energy conservation analysis. The temperature of the cold side, T c , was stabilized by a precise circulating thermostat (£0.1°C) in a temperature range from 5°C to 90°C. The amount of heat absorbed by a coolant flowing through the heat sink was measured by the calibrated and certified heat flow meter with an accuracy better than 1%. The temperature of the hot side, T h , was forced to assumed temperature (T max = 450°C) by an electric heater with known power (P h = 0-600 W) with ample thermal insulation. The electrical power was used in calculations. The TE module, heaters and cooling plate were placed in an adiabatic vacuum chamber. The load characteristics of the module were evaluated using an electronically controlled current source as a load. The apparatus may be used to determine the essential parameters of TE modules (open circuit voltage, U oc , short circuit current, I sc , internal electrical resistance, R int , thermal resistance, R th , power density, and efficiency, g, as a function of T c and T h ). Several commercially available TE modules based on Bi 2 Te 3 and Sb 2 Te 3 alloys were tested. The measurements confirmed that the constructed apparatus was highly accurate, stable and yielded reproducible results; therefore, it is a reliable tool for the development of thermoelectric generators.