Measurements were made of Bi diffusion in nanocrystalline material and thin films. The results showed that diffusion in nanocrystalline samples could be enhanced by more than 10 orders of magnitude with respect to that in monocrystalline material. The results for nanocrystalline material could be described by:

D (m2/s) = 1.8 x 10-5exp[-1.0(eV)/kT]

while those for the grain boundaries of thin films could be described by:

D (m2/s) = 2.43 x 10-8exp[-0.99(eV)/kT]

The grain boundaries in nanocrystalline material had a higher free energy and volume than those of conventional grain boundaries. Relaxation could also take place in nanocrystalline material. The tracer diffusivity in nanocrystalline samples at 100C was 2.3 x 10-19m2/s, while the intrinsic diffusivity was 1.1 x 10-20m2/s. The tracer diffusivity in thin film samples at 100C was 1.2 x 10-21m2/s.

H.J.Höfler, R.S.Averback, H.Hahn, H.Gleiter: Journal of Applied Physics, 1993, 74[6], 3832-9