Temperature and orientation dependences of the grain-boundary diffusion coefficient of antimony in copper bicrystals

An investigation is made of the diffusion of antimony through the bulk and along grain boundaries in copper bicrystals containing a symmetric [100] misorientation boundary with misorientation angles from 20 to 37.2 degrees. The bicrystals are grown by the method of horizontal zone recrystallization. The temperature range for these studies is 480-580 degrees C, where the solubility of Sb in Cu is about 6 atomic % and practically temperature-independent. The concentration profiles are obtained by x-ray spectral microanalysis, and the grain-boundary diffusion parameters are computed by the method of Whipple and Suzuoka. The orientation dependence of the triple product P=(s) delta D-b (where s is the segregation coefficient, delta the width of the grain boundary, and D-b the grain-boundary diffusion coefficient) is nonmonotonic, with a maximum for the special Sigma 5 misorientation boundary (36.9 degrees). The effective activation energy for grain-boundary diffusion ranges from similar to 70 kJ/mol for Sigma 5 to 140 kJ/mol for general boundaries. (C) 1997 American Institute of Physics.