Thermoelectric Power of Dilute Copper Alloys. II

Abstract

The work of Blatt and Kropschot was extended to dilute CuAg and CuAu alloys; simultaneous measurements of the thermopower and thermal conductivity were made on CuSn alloys. The decomposition of the absolute thermopower of copper into diffusion ${S}_{d}$ and phonon drag ${S}_{g}$ contributions proposed by Blatt and Kropschot was verified. It is based on the observed quenching of ${S}_{g}$ by large-mass solutes due to anisobaric phonon scattering. It was found that ${S}_{g}$ is completely suppressed by approximately 1 at.% of Ag or Sn and by 0.4 at.% of Au. In the temperature region ($T\ensuremath{\simeq}60\ifmmode^\circ\else\textdegree\fi{}$K) where anisobaric scattering is important in limiting the lattice conduction ${\ensuremath{\kappa}}_{g}$, it was observed that ${\ensuremath{\kappa}}_{g}$ is reduced considerably less than ${S}_{g}$. It is suggested that this is due to the characteristic dispersion of phonons of large wave vector. At low temperatures, where the Debye model holds, comparison of ${S}_{g}$ and ${S}_{d}$ with specific-heat data leads to the conclusion that the umklapp contribution ${{S}_{g}}^{U}$ is 25% larger in magnitude than the normal contribution ${{S}_{g}}^{N}$. This is in agreement with estimates by Ziman of the relative importance of normal and umklapp processes in copper.