Synthesis, structure and properties of responsive solid-state materials

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Responsive materials exhibit unique physical responses under constant or variable applied forces or fields. Combination of such physical responses with outstanding mechanical properties of solid-state phases yields functional materials that find applications both at the industrial and consumer levels. The research will focus on two areas of responsive solid-state materials: magnetocaloric and thermoelectric phases. Magnetocaloric materials respond by changing their temperature when the magnetic field is varied and can be used for magnetic cooling, which offers better efficiency than conventional vapour-cycle refrigeration. Thermoelectric materials generate voltage when subject to a temperature gradient or perform cooling/heating when current is passed through them. Currently, thermoelectric materials are used for power generation in deep-space mission, remote weather and navigation systems and for cooling in electronic devices and car seats. And since half of the energy is lost as a waste heat, research efforts start to focus on recovering some of this energy, especially in cars and ovens, through thermoelectric generators. The short term goals of the proposed research will be discovery and characterization of novel, high-performance thermoelectric and magnetocaloric materials. In the long run, we aim to develop a deeper understanding of the composition-structure-property relationship in these types of materials, and to use the obtained knowledge for the rapid and targeted design of new materials. Among the thermoelectric materials, we will focus on the synthesis of lanthanoid (Ln) antimonide and bismuthide suboxides with the general formula Lnm(Sb,Bi)nOm. These phases may be classified as "electron-crystal phonon-glass" materials, as they are good electrical conductors, while their thermal conductivity is very low and is approaching that of amorphous materials. Some of the Lnm(Sb,Bi)nOm materials display novel charge transport mechanisms and we want to use these mechanisms to optimize their thermoelectric properties. The research on the Lnm(Sb,Bi)nOm suboxides was initiated in our group and we would like to maintain our leading role in this area. In the magnetocaloric field, we will pursue targeted synthesis of new polar intermetallic materials, in which a ferromagnetic ordering is coupled to a structural transition at or near room temperature. We proposed to utilize the valence electron concentration and size effects to tune structural and magnetic properties of new magnetocaloric materials. These approaches were pioneered in our group and we will apply them to prepare novel high-performance phases.