Estimation of grain boundary diffusivity in cation-doped polycrystalline alumina

The grain boundary diffusion coefficient in uncloped and 0. 1 mol% cation-doped Al2O3 was estimated from the densification behavior during the final stage sintering. The densification rate was monitored from room temperature to the sintering temperature using a laser-scanning micrometer, which allows in-situ, non-contact measuring of the specimen's dimensions. The grain boundary diffusivity in Al2O3 is sensitively affected by the doped cation which segregates at the grain boundaries. A first-principle molecular orbital calculation indicates that the doping effect on the grain boundary diffusivity is related to the ionicity in Al2O3; the grain boundary diffusivity correlates well with the net charge of the Al and O ions in the cation-doped Al2O3.