Thermoelectric magnetic sulfides


The main goal of the project is to explore, select and optimize new thermoelectric materials enabling efficient and affordable conversion of heat into electricity using waste heat in the so-called medium temperature range, i.e. between room temperature and about 400 °C. This temperature window has the greatest potential for waste heat recovery due to the energy balance of modern society. With regard to the necessary affordability, processing and toxicity of the constitutive elements of the relevant thermoelectric materials, we will focus on affordable sulfide ternary systems based on copper, iron and chromium. The first group of investigated materials will consist of chemically optimized chalcopyrite (CuFeS2), which has a three-dimensional character, is strongly antiferromagnetic and exhibits interesting thermoelectric properties, especially with n-type doping. The second group will be based on layered chromium sulfide CuCrS2 in which we can expect high thermoelectric effectivity with p-type doping. As high absolute value of thermoelectric coefficient (whose absolute magnitude is the most important physical parameter for thermoelectric conversion efficiency with respect to thermoelectric conversion efficiency defined by Figure of merit ZT), low electrical resistance and low thermal conductivity are prerequisites of effective thermoelectric conversion, the interplay between magnetic interactions, crystal structure and thermoelectric response due to the constitutive role of magnetic metals will be studied. Targeted materials will be optimized through magnetic doping and nanostructuring aimed at reducing thermal conductivity. In addition to basic chemical, morphological and especially thermoelectric properties in a wide range of temperatures, the materials will also be investigated in a magnetic field and using special techniques, including extreme conditions. Experimental research will be supplemented by calculations of electronic structures and transport coefficients, which will allow both to interpret the obtained experimental data and to effectively anticipate the possibilities of suitable substitutions and modifications.