Thermoelectric Transport Properties of Novel Nanoscaled Materials via Homemade and Commercial Apparatus Measurements

Abstract

Thermoelectric (TE) materials are of broad interest for alternate energy applications, specifically waste heat applications, as well as solid-state refrigeration. The efficiency of TE materials can be improved through either the enhancement of the Seebeck coefficient and electrical conductivity, or through the reduction of the thermal conductivity, k, specifically the lattice portion of thermal conductivity, klatt. Nanostructuring has been proven to reduce klatt and therefore increase efficiency. The inability to accurately model the lattice and electronic contributions to k makes optimizing the reduction of klatt difficult. This work demonstrates that the lattice and electronic contributions to k in nanostructured materials can be directly measured experimentally by separating the contributions using magnetic field. We use this technique along with other characterization techniques to determine the effects of doping Ce, Sm, and Ho into Bi88Sb12. Along with enhancing the efficiency of the material, TE devices must be thermally stable in the temperature range of operation. Therefore we also study the effects of temperature cycling, annealing, oxidation, and diffusion barriers on TE devices. These studies are accomplished through both homemade and commercially available measurement equipment.