A theoretical study was made of the modelling of Ti in-diffusion. It was assumed that the Ti activation energy exhibited a spatial dependence upon the diffusion depth. This variation was the result of Li concentration depletion, due to its out-diffusion. The model also considered that Ti diffusion occurred via an ion-exchange process in which Ti4+ ions substituted for Nb5+ ions that were located in Li sites. The resultant diffusion equation was solved numerically by using initial and boundary conditions which corresponded closely to experimental situations. These assumptions led to the prediction of highly asymmetrical Ti concentration profiles, as observed experimentally.

H.F.Da Silva Filho, S.C.Zilio, F.D.Nunes: Journal of Physics - Condensed Matter, 1997, 9[2], 357-64