Control of high temperature mass transport phenomena through grain boundaries in oxide ceramics based on grain boundary chemical composition and external electric field

The present paper briefly summarizes our recent research on high-temperature mass transport phenomena through grain boundaries in oxide ceramics. We have proposed two techniques to control grain boundary mass transport in oxide ceramics: one is to change the chemical composition in the grain boundary, and the other is to apply an external electric field or current to the material. The former effect is attributed to grain boundary segregation of doped cations, and is effective in improving the sinterability and high-temperature plastic deformability of oxide ceramics. The importance of the chemical bonding state of grain boundaries has also been pointed out. The latter effect yields a drastic enhancement of diffusional mass transport through grain boundaries. Athermal effect, in which the electric field/current itself provides the acceleration of grain boundary diffusion, seemed to exist, besides Joule heating effect.