Atomistic study of abnormal grain growth structure in BaTiO3 by transmission electron microscopy and scanning transmission electron microscopy

An accurate understanding of the atomistic structure of interfaces is crucial to explain the mechanism of abnormal grain growth (AGG) in polycrystalline materials. In this work we investigated the atomistic structure of interfaces in a Ti excess BaTiO3 by transmission electron microscopy (TEM) and Cs-corrected scanning transmission electron microscopy (STEM). After sintering at 1300 °C in air, the Ti excess BaTiO3 shows typical AGG morphology with {1 1 1} twin lamellae and {1 1 1} faceted grain boundaries. A sub-nanometer Ti-rich intergranular phase and a second phase, Ba4Ti10Al2O27, at the {1 1 1} faceted grain boundaries were indentified. The intergranular phase and the Ba4Ti10Al2O27 exhibit epitaxial relationships with BaTiO3 in stacking sequences of {1 1 1} BaTiO3/intergranular phase/(1 0 0) Ba4Ti10Al2O27 and {1 1 1} BaTiO3/(1 0 0) Ba4Ti10Al2O27. Additionally, two orientation relationships were identified, [1 1 0] BaTiO3 // [0 1¯ 0] Ba4Ti10Al2O27 and [1 1 0] BaTiO3 // [0 1 0] Ba4Ti10Al2O27. The intergranular phase and Ba4Ti10Al2O27 are also shown to exhibit strong structural similarities. Effects of the interfaces on AGG are proposed.