Synthesis and physical characterization of thermoelectric single crystals

Abstract

There is much current interest in thermoelectric devices for sustainable energy. This thesis describes a research project on the synthesis and physical characterization of thermoelectric single crystals. 1In₄Se₃-[delta] crystals were grown by different methods including the use of a floating zone furnace and a three-zone furnace, as well as different initial compositions. The samples obtained each time, either crystalline or powder, were analyzed using x-ray diffraction to find the phases present, and orientations in the case of crystals. The crystals were studied by the means of neutron scattering at Oak Ridge National Laboratory, and the results presented differences from previous literature reports and a non-zero intensity of forbidden Bragg peaks was noted. Simulations of the effect of Se vacancies in the crystal were executed to explore this last phenomenon. Measurements of the electrical resistivity p and Seebeck coefficient S of the crystal related to the figure of merit ZT = S₂T/pk were compared with the values presented by other groups.