In situ topochemically converted 2D BaTiO₃ polycrystals with multifarious zone axes

BaTiO₃ polycrystals with platelike morphology are prepared on the basis of an in situ topochemical conversion mechanism from a layered titanate H_4x/3Ti_2−x/3□_x/3O₄·nH₂O (HTO) single crystal as the precursor and different barium compounds. BaTiO₃ polycrystals present single-crystal-like electron diffraction points, indicating mesocrystals. The different BaTiO₃ mesocrystals present non-uniform zone axes; however, the [100] zone axis of 60% is dominant owing to the intermediate mesocrystalline TiO₂ polymorphs derived from the HTO precursors with the allied TiO₆ octahedral layers. First-principles density functional theory calculations were performed for the verification of the most easily generated BaTiO₃(100) surface compared to the other surfaces. BaTiO₃ mesocrystals with high purity and multifarious zone axes can be formed using the HTO crystals as a precursor. Furthermore, [100]-textured BaTiO₃ ceramics with high density, enhanced degree of orientation, and high piezoelectric constant are fabricated via templated grain growth, using the BaTiO₃ mesocrystals as templates. Textured BaTiO₃ ceramics with excellent physical properties are developed mainly by the growth of oriented template BaTiO₃ mesocrystals with the [100] zone axis at the expense of matrix grains, which are BaTiO₃ mesocrystals with the non-[100] zone axis. This novel strategy can control the desired orientation of textured materials with high piezoelectric properties.