The thermoelectric power of alloys-a modified Nordheim-Gorter relation

Abstract

A modified Nordheim-Gorter relation is established which involves a characteristic thermopower of the deviation from Matthiessen's rule and the deviation itself. The relation shows why the characteristic thermopower of the solute, obtained at high temperatures via the normal Nordheim-Gorter rule is generally erroneous as also are previous estimates of the phonon drag thermopower in dilute alloys. A two band model is invoked in considering the validity of the modified Nordheim-Gorter rule and it is established that when any anisotropy of electron-phonon scattering is temperature dependent, the diffusion thermopower of pure metals is nonlinear in temperature. It is also shown that the apparent phonon drag enhancement observed in Al alloys may be explained in terms of diffusion thermoelectricity.