Diffusion induced grain-boundary migration (DIGM) can occur when a polycrystal becomes chemically unstable at high temperatures. In the present investigation, we studied the effect of grain boundary structure, either rough or faceted, on DIGM in $BaTiO_3$. $BaTiO_3$ power compacts were sintered at 1300℃ for 100 h in air and annealed at 1250$^\circ$C for 50 h in $H_2$ to prepare samples with rough grain boundaries. Some of the air-sintered and $H_2$-annealed samples were reannealed at $1250^\circ C$ for 50 h in air to prepare samples with faceted boundaries. $SrTiO_3$ paticles of ~50 $mu m$ in size were scattered on the polished surfaces of the two kinds of $BaTiO_3$ samples and annealed at 1250$^\circ$C for 40 h in air for the samples with faceted boundaries and in $H_2$ for those with rough boundaries. In the air-sintered and $H_2$ -annealed samples, an intensive grain boundary migration occurred. This migration of rough boundaries is due to the coherency strain energy stored in a solid-solution layer formed at the surface of the shrinking grain, as in the case of DIGM in other materials. In contrast, grain-boundary migration hardly occurred in the air-reannealed $BaTiO_3$ samples with faceted boundaries. This migration suppression of faceted boundaries may be explained in terms of low boundary mobility.
An air-annealed $BaTio_3$ sample with $PbTiO_3$ particles, however, the faceted boundaries migrated during subsequent air-annealing. Comparision of the coherency strain energies of $BaTiO_3-SrTiO_3$ and $BaTiO_3-PbTiO_3$ suggests that high coherency strain energy can also induce DIGM.
The present experimental results demonstrate that DIGM is strongly affected by boundary structure and can be strongly suppressed by structural transition of boundaries from rough to faceted.
