Thermoelectric Power of Aluminum and Dilute Aluminum Alloys

The thermoelectric power of dilute alloys of aluminum with Ag, Zn, Mg, and Au has been measured versus pure aluminum between 4.2 and 460°K. The solute concentrations were in general 0.1 at.% or smaller. The absolute thermopower of high-purity Al has been measured between 4.2 and 300°K. The phonon-drag component $S^g$ in Al is negative, with a peak at about 70°K. At temperatures above 40 to 80°K, depending on the composition, the alloys show the usual reduction in the phonon-drag thermopower. However, at lower temperatures, an increase in $\left|S^g\right|$ due to alloying is observed in all specimens. It is suggested that this anomaly in the phonon-drag thermopower of the dilute aluminum alloys is because of the anisotropy of the electron scattering. The results can be explained with a relaxation time for electron-phonon scattering which is shorter in the third band than in the main portion of the Fermi surface, in combination with an isotropic electron-impurity interaction. The electron diffusion component $S^e$ in Al is negative. All alloys show a positive change in $S^e$.