Temperature Dependence of the Elastic Constants of Cu, Ag, and Au above Room Temperature

TLDR

The adiabatic elastic constants of Cu, Ag, and Au were measured from 300 K to ~800 K with ultrasonic pulse‑echo, and the resulting compressibilities were used to compute the dilational specific‑heat term, confirming the Nernst‑Lindemann relation up to 800 K. The measured elastic constants agree with prior data at room temperature, decrease linearly with temperature up to 800 K (and up to 1000 K for Ag), and the derived compressibilities confirm that the Nernst‑Lindemann relation accurately predicts the dilational specific‑heat term for Cu, Ag, and Au.

Abstract

The adiabatic elastic constants c44, ½(c11−c12), and ½(c11+c12+2c44) have been measured for copper, silver, and gold over the temperature range from 300° to about 800°K using the conventional ultrasonic pulse-echo technique. The room-temperature values of the stiffness coefficients are shown to be in acceptable agreement with previously published data for the noble metals. Over the entire range from 300° to 800°K, it is found that, to a remarkably good approximation, the elastic constants for all three metals decrease linearly with temperature. Additional evidence is presented to show that the linear temperature dependence of the elastic constants for silver extends to at least 1000°K, i.e., to within 80% of the absolute melting temperature. The isothermal compressibilities calculated from the elastic constant data are used to evaluate the dilational term in the specific heat, Cdil=Cp−Cv, and it is established that the approximate Nernst-Lindemann relation for estimating Cdil is valid for Cu, Ag, and Au at least up to 800°K.