Thermoelectric Power and Electron Scattering in Metal Alloys

The thermoelectric power of a metal depends on the details of how the current carriers in the metal are scattered by the various deviations of the crystal from a perfect lattice. A semiempirical theory of thermoelectric power in metal alloys is described, which is based on a formula due to Mott and others. The theory relates absolute thermopower to the energy dependence of the scattering cross section $Q_i\left(\epsilon \right)$ of a lattice imperfection, and deduces numerical values for the first few "scattering coefficients" in a Taylor expansion of $Q_i\left(\epsilon \right)$ about the Fermi level ${\mu }_0$ in the pure solvent metal. The few known empirical "rules" of thermoelectric power in binary alloys of Cu, Ag, and Au, of alkali metals, and of Al are interpreted in terms of these scattering coefficients. The correlation with high-temperature thermoelectric properties of such alloys is shown to be quite satisfactory, but the low-temperature properties present several difficulties which cannot be properly discussed without further extensive experiments at very low temperatures. The usefulness of thermoelectricity as a tool for studying the nature of lattice imperfections is discussed briefly.