Chemical Control Of The Grain-Boundary Migration Of SrTiO3 in The SrTiO3-BaTiO3-CaTiO3 System

Abstract

The grain-boundary migration induced by chemical instability has been studied in SrTiO3. Sintered SrTiO3 has been packed with various BaTiO3/CaTiO3 powder mixtures and annealed at 1400-degrees-C for various times. At the surface region of most SrTiO3 specimens, the grain boundary has migrated with the diffusion of Ba and Ca ions. The ratio of Ba and Ca ions present in the migrated region varies with the depth from the surface and the packing-powder composition, and is not equal to the cation ratio of packing powder. When the Ba/Ca ratio of packing powder is 1, cessation of migration has been observed. The composition of the area without migration is estimated to be approximately equal to the composition for the matching of crystal lattices between the original grain (SrTiO3) and the layer formed by diffusion of Ba and Ca ions. The coherency strain energy induced by diffusion of solute atoms is believed to be the major driving force for the grain-boundary migration of SrTiO3 under the chemical instability. The grain-boundary migration can be accordingly controlled by lattice parameter change and matching.