Experimental studies of the thermoelectric properties of microstructured and nanostructured lead salts

Abstract

Thermoelectric devices allow for direct conversion between thermal and electrical energy. There applications, however, are severely limited by their inefficiency. A reduction in thermal conductivity of a material potentially enhances its overall thermoelectric performance and can improve the efficiency of thermoelectric devices. Thermal conductivity can be reduced by boundary phonon scattering for materials in which the grain size is comparable to or less than the phonon mean free path. Samples of PbTe and PbSe were prepared by hot pressing nano-size and micro-sized particles and the thermal diffusivity, the Seebeck coefficient, and the electric conductivity of the samples were measured. The samples made from the nano-sized particles showed no reduction in thermal conductivity and no enhancement of thermoelectric properties. It is suspected that the grain growth occurred during the hot pressing stage, resulting in grains sizes larger than the original particle. The grains may have grown substantially larger than the phonon mean free path. Grains of this dimension are not effective at scattering phonons.