Thermoelectric materials with embedded nanoparticles- An effective medium approach

The effect of adding spherical nano-particles inside a host matrix is investigated using the coherent potential approximation. A parabolic band structure is assumed for the host matrix and it is shown that nano-particles can modify the effective mass by up to 20\% when their volume fraction is about 10\%. The effective band-structure can be fitted by the standard non-parabolic relation, resulting in the negative non-parabolic coefficients in the case of barrier type nano-particles. Interesting peaks have been observed in the group velocity curve versus energy when the nano-particles are deep wells and their volume fraction is more than few percent. We show that using a high volume fraction ($\sim$5\%) of relatively small ($\sim$1nm) uniform size nano-particles the power factor can be enhanced significantly especially at low temperatures.