We study the effect of electron and phonon interface scattering on the thermoelectric properties of disordered, polycrystalline materials (with grain sizes larger than electron and phonons' mean free path). Interface scattering of electrons is treated with a Landauer approach, while that of phonons if treated with the diffuse mismatch model. The interface scattering is embedded within a diffusive model of bulk transport, and we show that, for randomly arranged interfaces, the overall system is well described by effective medium theory. Using bulk parameters similar to those of PbTe and a square barrier potential for the interface electron scattering, we identify the interface scattering parameters for which the figure of merit $ZT$ is increased. We find the electronic scattering is generally detrimental due to a reduction in electrical conductivity; however for sufficiently weak electronic interface scattering, $ZT$ is enhanced due to phonon interface scattering.
Citation: Japanese Journal of Applied Physics
Pub Type: Journals