Diffusion of heterovalent solutes in liquid silver

Abstract

The diffusion of trace amounts of indium and antimony in liquid silver has been measured in the temperature interval 975°C–1275°C. The diffusion coefficients may be expressed as a function of temperature in the following form D In = 5.75 × 10 −4 exp (−6760) RT cm 2/sec D sb = 4.06 × 10 −4 exp (−5700 RT cm 2/sec When compared with the previously determined diffusivities for tin and silver in liquid silver, it is seen that there is a monotonie increase in diffusivity as a given temperature as one increases the relative valence Z of the solute. Thus Ag < D In < D Sn < D sn < D sb and Z equals 0, + 2, +3 and +4 respectively for Ag, In, Sn and Sb. There also appears to be a monotonie decrease in the activation energy when one considers the series from silver to antimony. This effect is generally the same as found for diffusion of these solutes in solid silver. The relative magnitude of the diffusion enhancement of the solutes is explained quite well by consideration of the added coulomb repulsion of the solute of higher valence in terms of a Thomas-Fermi model if one invokes either the fluctuation model as proposed by one of the authors or the hole theory of diffusion. A fluctuation model which invokes the concept of a critical fluctuation cannot be reconciled with the experiments.