Thickness of Cubic Surface Phase on Barium Titanate Single‐Crystalline Grains

The crystallographic structure of BaTiO 3 particles prepared by conventional solid‐state reaction has been investigated by X‐ray diffractometry and dielectric measurements. The systematic analysis of the diffraction pattern has clearly shown the coexistence of tetragonal and cubic phases at room temperature. The relative amount of cubic phase increases and the dielectric constant decreases with decreasing particle size. These experimental results are consistent with the model that the cubic phase is located at the surface of BaTiO 3 grains. The thickness of the surface layer is estimated to be approximately 5 nm, irrespective of the grain size.