Diffusion of bismuth and gold in nanocrystalline copper

Measurements of Bi and Au diffusion in nanocrystalline (n-) Cu and of Bi in copper thin films have been performed. The results show that (a) the diffusivity in n-Cu can be enhanced by more than ten orders of magnitude with respect to that in single-crystalline Cu. (b) Grain boundaries in n-Cu have a higher free energy and volume than conventional grain boundaries. (c) Relaxation can take place in n-Cu. (d) Diffusion measurements in n-materials represent a convenient means to determine thermodynamic properties such as grain boundary energies, solubilities, heats of segregation, and solution.