The parameter which described the chemical diffusion of Ag along the tilt axes of a series of [001] symmetrical tilt boundaries, in the Au-Ag system, was studied as a function of temperature and tilt angle at relatively low temperatures. Sixteen boundaries were studied by using a surface accumulation method. The parameter was found to vary quite smoothly as a function of tilt angle. That is, there were no sharp minima or cusps at low- misorientations. The activation energies were found to be smooth functions of the tilt angle, and to range from 0.70 to 0.85eV. The pre-exponential factors in the Arrhenius expression for the grain boundary diffusion parameter were some 3 orders of magnitude smaller than many reported values for diffusion at higher temperatures. In the case of a typical boundary, the diffusivity was described by:

D(m3/s) = 4.8 x 10-18exp[-0.68(eV)/kT]

Q.Ma, R.W.Balluffi: Acta Metallurgica et Materialia, 1993, 41[1], 133-41