Low-Temperature Transport Properties of Copper and Its Dilute Alloys: Pure Copper, Annealed and Cold-Drawn

Abstract

Experimental results between 4\ifmmode^\circ\else\textdegree\fi{} and 300\ifmmode^\circ\else\textdegree\fi{}K are given for (1) the thermal conductivity, electrical resistivity, and thermoelectric force and power of two high-purity coppers, one annealed and one cold-drawn 26%; and (2) the electrical resistivity of a series of seven samples of high-purity copper cold-drawn between 0% and 20% elongation. The total electronic thermal resistivities each consist of three terms: the intrinsic resistivity, ${W}_{i}$; the imperfection resistivity, ${W}_{0}$; and a deviation term, ${W}_{i0}$, indicating the departure from strict additivity of ${W}_{i}$ and ${W}_{0}$. The intrinsic thermal resistivity and intrinsic electrical resistivity vary as ${T}^{2.8}$ and ${T}^{4.5}$, respectively, contrary to the predictions of the usual transport theory using Bloch approximations and assumptions. The resistivity of pure copper is 1.545 \ensuremath{\mu}ohm cm at 0\ifmmode^\circ\else\textdegree\fi{}C. The increase in imperfection electrical resistivity is approximately linear with increase in cold-drawn elongation. However, the added resistivity is not independent of temperature (Matthiessen's rule), but about twice as great at the ice point as it is at 4\ifmmode^\circ\else\textdegree\fi{}K. The change in thermoelectric power with drawing is positive at the lower temperatures, but negative above 38\ifmmode^\circ\else\textdegree\fi{}K. The Lorenz number does not approach the Sommerfeld value at the lowest temperatures, but flattens out to a value considerably smaller. A qualitative discussion for each of the various effects is given.