A theoretical attempt was made to model the effects of segregation upon grain boundary diffusion. By assuming realistic numerical values for the segregation and diffusion parameters, the typical behavior of O self-diffusion coefficients in alumina was plotted on an Arrhenius diagram and was compared with experimental data. It was found that the segregation of impurities and point defects could lead to activation enthalpies for diffusion that were higher in the grain boundary than in the volume. It was concluded that, in such cases, grain boundary diffusion did not control the kinetics of matter transport at low temperatures but did so over a range of temperatures that could be difficult to determine accurately.

C.J.A.Monty: Materials Science Forum, 1996, 207-209, 633-6