Paper TF1-ThA8
From Uncontrolled and Controlled Size and Shape Intercalated Nanostructures to Bulk Materials for Thermoelectric Device Applications: Old and New Materials - New Techniques

Thursday, October 18, 2007, 4:20 pm, Room 602/603

The properties of all materials are highly dependent on structure, composition, size and shape. As we seek to explore and utilize novel phenomenon at the nano, 2-dimensional and 3-dimensional scale, a basic understanding of structure/composition/size/shape property relations alone are not enough unless this understanding is made in the context of a specific device and in relation to the practical, economic considerations. This investigation requires a highly integrated approach to all aspects of development of these integrated devices, including theoretical prediction, synthesis, processing and characterization in concert with device design, optimization and implementation. Theoretical and experimental results predicted that the nano-scale materials have better thermoelectric properties that bulk materials.¹ Previous theoretical work on the effect of the grain boundaries in polycrystalline materials indicated that the scattering of the phonons in smaller grains could be very beneficial for the efficiency of the thermoelectric materials.² This presentation will highlight some new directions in size and shape controlled nanostructure (grains) and bulk thermoelectric materials research based on our theoretical and experimental investigations. Specific configurations where size and shape of the nanostructures that will constitue the bulk materials are controlled during fabrication will be discussed. Preliminary calculations of the electronic and thermal properties as a function of the composition, size and shape of the intercalated nanostructure will be also presented. We will also describe the synthesis techniques of the nanostructures and the method to incorporate these structures into bulk materials during fabrication. However, the challenge remains to achieve higher performance results in integrated systems in order to more rapidly incorporate them into standard thermoelectric devices.

¹M. S. Dresselhaus, J. P. Heremans, in Thermoelectrics Handbook: Macro to Nano (Ed: D. M. Rowe), Taylor and Francis, CRC, Boca Raton, FL 2006, Ch. 39, p. 39-1-39-24.
²J. W. Sharp et al , Boundary Scattering and the Thermoelectric Figure of Merit, Phys. Stat. Sol. (a) 187, No. 2, 507-516 (2001).