Abstract
Thermoelectricity is a physical effect related to the direct conversion between thermal and electrical energy. To improve the thermoelectric efficiency, the electronic properties of the materials must be optimized to get a large Seebeck coefficient and a low electrical resistivity while lowering the thermal conductivity. One of the optimization ways is to reduce the dimensionality of the materials to decrease the phonon contribution to the thermal conductivity. Silicides are promising materials because of their low toxicity and cost. Among them, chromium disilicide, CrSi2, shows interesting electronic transport properties, but a too high thermal conductivity, limiting its performance. The objective of this thesis is to study the thermoelectric properties of this compound with various forms, single crystal, thin film and nanowire.For this purpose, the chromium disilicide was elaborated in the forms of single crystal by the Bridgman method, thin film by sputtering, and nanowires by chemical vapor deposition. These elaboration routes have been associated with characterization techniques specific to each form in order to study the relationship between the physical properties and the microstructure of the material. By coupling theoretical models with thermoelectric measurements, the mechanisms of electronic and thermal transports have been determined. The vibrational study was completed by the first inelastic neutron scattering measurement on CrSi2 single crystal and nano-powder. In the case of thin films, the effect of the crystallinity state and the thickness has been studied. Finally, in the case of nanowires, a micro-device has been designed to measure the properties of a single nanowire. The presented results open interesting perspectives to improve the thermoelectric properties of CrSi2.