Since the 1950s, increased interest in thermoelectric materials has been observed. But the discovery of new phenomena and innovative methods of production at the beginning of the 21st century has led to significant growth in the field of thermoelectric materials and their applications. The mentioned progress is inextricably connected with new requirements for energy production as a result of fossil fuel depletion and global efforts to overcome this problem by developing and implementing renewable energy sources.
The aim of this study was to obtain thermoelectric material based on lead telluride with the highest values of thermoelectric parameters and the subsequent manufacturing the thermoelectric generator based on this material.
Thermoelectric generators are devices that use the Seebeck effect to convert thermal energy into electricity. So they can be used for example to power satellites and spacecrafts, to power or charge variety of small devices, such as flashlights, cameras, night vision goggles, watches, cell phones, etc. One of the recent interests is a thermoelectric generator which could convert recovered heat into electricity in car exhaust systems. As it was already said, this last use makes thermoelectric materials an attractive source of renewable energy, and thus an interesting alternative to traditional sources of energy derived mostly from fossil fuels.
As part of work, we prepared a few crystals of lead telluride: undoped, doped with Cr, I and doped both with Cr and I by the Bridgman method. Then the following tests were carried out to allow for calculation of their electric and thermoelectric parameters: the Hall measurements: type of conductivity, carrier mobility, concentration, resistance (from which then electrical conductivity was determined), thermal conductivity and the Seebeck coefficient. Then, based on these measurements, the thermoelectric figure of merit (ZT) of these materials was determined. ZT is a factor which determines the quality of the thermoelectric material.
XRD and SEM studies of selected samples were also carried out.
In the further works we will subject the obtained crystals to "mechanical alloying" method and subsequent pressing and sintering of the material, in order to obtain material with even better thermoelectric performance.
It is believed that achieving figure of merit ≥ 3 will enable the construction of cost-effective thermogenerators of high performance. Therefore, materials with improved electrical properties and materials with low thermal conductivity coefficient are systematically explored.
State-of-the-art methods to achieve these goals include mechanical alloying - one of the nanostructure manufacturing techniques, which is based on two processes: mechanical grinding of powders and sintering of cold shredded pieces, hot pressing and its variants such as hot isostatic pressing, melt spinning method, which consists of casting molten stream on rapidly rotating metal drum and the rapid cooling from the liquid by centrifugation, and spark plasma sintering method.
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