Self-Diffusion in Silver-Gold Solid Solutions

Abstract

The diffusion of silver and gold tracers in silver-gold in crystals of 0, 8, 17, 35, 50, 66, 83, 94 and 100 at. % gold has been measured. It is shown that the limiting error in such measurements is due to temperature uncertainty rather than to the sectioning process. The activation energies obtained do not vary in proportion to the melting point or heat of fusion, and the deviations cannot be rectified in terms of lattice parameter arguments. The activation energies in the pure metals are better accounted for by the theory of Turnbull and Hoffman than by that of Swalin. The suggestion that the vacancy migration energy should vary as (cu -Cn) is not confirmed. From the change in frequency factor with composition it is deduced that the activation entropy of migration of a vacancy decreases linearly with composition by 1.5R from pure silver to pure gold. The dependence of diffusion coefficient on gold content is compared with the theories of Hoffman, Turnbull, and Hart, of Reiss, of Manning, and of Lidiard, and impurity correlation factors of reasonable magnitudes are obtained. Particularly difficult to treat, however, is the decrease in diffusion coefficients resulting from additions of the rapid diffuser silver to the slow diffuser gold. An experiment to measure the effects of vacancy flux directly is proposed.

25th Anniversary Article: Galvanic Replacement: A Simple and Versatile Route to Hollow Nanostructures with Tunable and Well‐Controlled Properties

“…For example, the value of D for the interdiffusion of atomic Au through a layer of Ag would increase from 10 −24 m 2 s −1 to 10 −19 m 2 s −1 as the temperature increases from room temperature to 100 °C. [ 79,80 ] Collectively, the degree of alloying increases with elevation of reaction temperature, thickening of A layer deposited on the template of metal B , and depression of the energy barrier to diffusion. In general, alloying is the basis for retaining the morphology of the original template during a galvanic replacement reaction ( Figure 3 A).…”

Environment-Sensitive Thermal Coarsening of Nanoporous Gold

“…This vacuum-annealing activation energy was nearly equal to that of lattice diffusion of gold (174.6 kJ/mol). 11,12) We presume that this difference arose as follows: In air, the surface adsorption of gas molecules promotes the surface diffusion of Au adatoms on NPG, which is the dominant mechanism of thermal coarsening in air (i.e. gas).…”

Experimental evidence for kinetically determined intermixed Volmer-Weber growth in thin-film deposition of Au on Ag(110)

“…Moreover, the IFME calculated for one single Ag x Au 1Ϫx alloy layer sandwiched between a Ag and a Au crystal predicts the interface to be unstable for the three low-index faces. 11 However, due to the very small RT diffusion coefficient D 300 K ϭ5.5ϫ10 Ϫ16 Å 2 /sec of Au impurities in pure Ag, 18 a thin Au film grown on a Ag crystal is not expected to dissolve into the Ag bulk at RT.…”