Relation between grain growth, densification and surface diffusion in solid state sintering - A direct observation

A direct observation of the grain growth and densification of BaTiO ₃ ceramics were made in a TEM equipped with an in-situ installed heating platform. Both real two-sphere and three-sphere models for BaTiO ₃ ceramics were found and parallel processes of the shrinkage between particles and the grain growth (coarsening) were observed during the heating process. Attempts of relating the grain growth and densification was made which reveals, though roughly, the close relation between the two competing process: they took place simultaneously and in parallel, therefore it is believed that the process took place via the same mass transport mechanism. Surface diffusion on the TiO ₂ particle surface was observed directly, which takes place with the co-motion of several lattice layers from a smaller grain onto the surface of an adjacent larger one. The surface diffusion was accompanied by the diminishing of a small grain, i.e., overall grain growth.