Nanostructuring and Porosity in Anisotropic Thermoelectric Materials Prepared by Bottom-Up Processing

Abstract

Nanostructuring has allowed for enhancement in the thermoelectric properties of materials as compared to that of the bulk. The presence of nano-scale inclusions or grains within a bulk matrix seems to be beneficial in certain cases. In addition, texturing and porosity in nanostructured thermoelectric materials are also important factors, and can directly affect the thermoelectric properties. Bottom-up processing allows for control of particle size and yield, as well as the quality of the nanocrystals, while densification by spark plasma sintering preserves the nano-inclusions within the dense bulk material without significant grain growth. Optimization of the synthesis as well as the densification parameters is therefore critical in obtaining dense materials. Materials with anisotropic crystal structures have additional challenges due to the possibility of grain alignment during densification, and the associated effects on the physical properties of the material. An understanding of these effects on the properties of state-of-art thermoelectric materials offers a platform for expanding the investigation into fundamental structural and transport properties of other material systems that have potential for thermoelectric applications.