The Effect of Grain Size and Volume Fraction on Charge Transport in Thermoelectric Nanocomposite of Bi2Te3-Sb2Te3

It was shown by D. J. Bergman and L. J. Fel (J. Appl. Phys. 85, 8205, 1999) that in a composite material thermoelectric power factor, the product of the square of the Seebeck coefficient and electrical conductivity, can be enhanced over that of the individual constituents, but the figure-of- merit cannot. It is expected that this predication fails in nanocomposites due to the size effects which are ignored in this theory. In order to study the charge carrier transport in nanocomposites, we have applied a method based on Coherent Potential Approximation within effective mass approach. The method takes into account the average grain size as well as the grain size distribution and volume fraction of the different constituent in the nanocomposite material. We have applied this method to hole transport in nanocomposite of Bi₂Te₃-Sb₂Te₃ and showed the dependency of hole scattering rate as a function of the grain size.