An intergranular layer was found in 0.4mol%Y-doped BaTiO3, which was sintered below the eutectic temperature in air. The layer possessed a crystal structure similar to Ba6Ti17O40 with a thickness of 0.7nm. Plate-like second phases of Ba6Ti17O40 were also observed at triple-grain junctions and an orientation relationship of [image omitted] and [image omitted] was determined between the tetragonal BaTiO3 and the monoclinic Ba6Ti17O40. The detailed structure of the interface between BaTiO3 and Ba6Ti17O40 was resolved by scanning transmission electron microscopy and high-resolution transmission electron microscopy investigations.

TEM and STEM Investigation of Grain Boundaries and Second Phases in Barium Titanate. S.J.Zheng, K.Du, X.H.Sang, X.L.Ma: Philosophical Magazine, 2007, 87[34], 5447-59