Determination of vacancy jump frequency ratios and correlation factors of impurity diffusion and estimation of vacancy-impurity binding Gibbs free energies in dilute silver-antimony alloys

Abstract

The dependences of intrinsic diffusion coefficients (DSb, DAg) and interdiffusion coefficients (D) upon temperature and composition in dilute AgSb alloys have been measured. The interdiffusion coefficients D(0) obtained with infinitely dilute solutions agree well with tracer data for D*Sb(0) from the literature. The ratio of the intrinsic diffusion coefficients was determined by applying the thin plate method. Within the error margins the ratio DSb/DAg can be regarded as independent of concentration up to 3 at.% Sb. The values of DSb/DAg(0) with infinitely dilute solutions decrease linearly with increasing temperature. The jump frequency ratios w4/w0, w2/w1 and w3/w1 were calculated according to the five-frequency model on the basis of the vacancy flow factor LAB/LBB(0), the ratio of tracer diffusion coefficients D*Sb/D*Ag(0) and the linear enhancement factor b1. From these the correlation factor fSb of impurity diffusion is obtained, which increases with temperature from 0.30 at 890 K to 0.49 at 1048 K, as expected. The binding Gibbs free energy delta g1 of a vacancy-antimony pair has been estimated using four different methods of evaluation using the values measured in the present paper and diffusion data from the literature. The temperature dependence of delta g1 is critically discussed.