Semko T. Nanocrystalline thermoelectric materials based on Pb (Sn)-Ag-Sb-Te compounds.

For active elements of thermoelectric converters in temperature range (150-500)°С widely used the lead telluride, due to the uniqueness of its physical and chemical properties, as well as the relatively simple technology of obtaining qualitative crystals. One of the most important problems of thermoelectric converters, and not only on the basis of PbTe, is their relatively low efficiency (4 - 8) %. One of the ways to solve it is to modify the properties of the material by doping, creating solid solutions and nanocrystalline materials.In the thesis investigated the thermoelectric properties of materials of Pb14Sn4Ag2Te20 and Pb16Sn2Ag2Te20 for the first time, the influence of technological factors on obtaining experimental samples on microstructure and temperature dependences of the coefficient of thermoelectric power, specific electrical conductivity and thermal conductivity coefficient have been established. It is shown that for optimization of PbTe thermoelectric parameters, the formation of solid solutions of Pb1-xAgxTe is more promising than that of PbTe:Ag doping, in which the acceptor activity of argentum atoms is poorly expressed as a result of the manifestation of amphoteric properties. The main factor which results in the production of materials of the Pb-Sn-Ag-Te system with low thermal conductivity (≈ 0.002 W/(cm K)) is that sample contain two-phases: in addition to the main phase of the structural type NaCl, exist the additional phase of Ag10.6Te7 which fixed by X-ray.