By using the serial sectioning technique, a study was made of the effect of a Cl2 pressure upon the diffusion of 198Au in single crystals. When diffusion annealing was carried out in a mixture of 1torr Cl2 and 400torr He, the (presumably) intrinsic Au diffusivity could be described, at temperatures ranging from 260 to 440C, by:

D (cm2/s) = 5.0 x 10-3 exp[-0.47(eV)/kT]

This indicated an interstitial diffusion mechanism. When diffusion annealing was carried out in an 0.7atmCl2 atmosphere, the Au diffusivity was depressed and the Arrhenius plot consisted of 2 approximately linear segments; with a break at about 300C. At temperatures ranging from 260 to 300C, the Au diffusivity could be described by:

D (cm2/s) = 14 exp[-0.87(eV)/kT]

Increasing the Cl2 pressure, to 2atm., depressed the Au diffusivity somewhat more and the break in the 2 linear segments of the Arrhenius plot shifted to 340C. The observed behavior was explained in terms of the effect of Cl upon the cation vacancy concentration.

A.P.Batra, A.L.Laskar, L.Slifkin: Journal of the Physics and Chemistry of Solids, 1969, 30[8], 2053-9