Epitaxial Assembly Involved in Growth of BaTiO₃ Nanocrystals under Hydrothermal Condition

Abstract

Epitaxial assembly involved in the formation of aggregates of single-crystalline barium titanate (BaTiO 3 ) nanoparticles under hydrothermal condition is reported. The aggregates of BaTiO 3 nanocrystals were synthesized by heating a mixture of barium hydroxide, Ba(OH) 2 , and titanium tetra-iso-propoxide, Ti(O i C 3 H 7 ) 4 , with a molar ratio of 1:1 : 1 resolved in water-ethanol solutions at 150 C for 2 h in autoclaves. The volume ratio of water/ethanol used as the solvent gives a significant influence on the amount of organic components contained in the precipitates after the reaction completed; a pure water solution left much organic components in the obtained BaTiO 3 nanoparticles aggregates, whereas a 1 : 1 (in volume ratio) water-ethanol solution yielded aggregates of BaTiO 3 nanoparticles with little organic components. Transmission electron microscopy (TEM) analyses provide definite evidence for the occurrence of epitaxial assembly of more than hundred BaTiO 3 nanocrystals with sizes of 40 -60 nm into an aggregation possessing crystallographically single-crystalline nature during the crystal growth under the hydrothermal condition.

Synthesis of Nano‐sized BaTiO3 Powders by the Rotary‐Hydrothermal Process

“…Generally, BaTiO 3 powders have been prepared by solid-state reaction via the calcinations of BaCO 3 and TiO 2 powders at temperatures above 1273 K. 4 However, this process leads to BaTiO 3 particles with uncontrolled and irregular morphologies, which limit the electrical properties of the resulting sintered ceramics. Recently, wet chemical processes such as the sol-gel method, [5][6][7] homogeneous precipitation (the oxalic acid method), 8 and the hydrothermal method [9][10][11][12][13] have been developed to improve the homogeneity and purity of BaTiO 3 powders. Because products prepared by solution-based processes such as the sol-gel method and homogeneous precipitation either are amorphous or represent precursor compounds, a heattreatment step at temperatures above 923 K is required in order to remove unreacted organics and form a pure crystalline phase.…”

Atomic‐Scale Characterization of Barium Titanate Powders Formed by the Hydrothermal Process

“…4,5 However, the resulting microstructure is not sufficient for microelectronic applications because of a lack of uniform, nanocrystalline BT powders. Recently, wet chemical methods such as the sol-gel method, 6,7 alkoxide synthesis, [8][9][10] and the hydrothermal method [11][12][13][14] have developed and have replaced the classical solid-state reaction for the synthesis of BT nanopowders. By these methods, nanosized BT powders have been synthesized, which makes the BaTiO 3 system very attractive for developing new electronic nanodevices.…”

Hydrothermal synthesis of nanocrystalline BaTiO3 particles and structural characterization by high-resolution transmission electron microscopy

“…The low-temperature hydrothermal synthesis of BT nanoparticles is normally carried out by suspending titania nanoparticles or titania gel in an aqueous Ba(OH) 2 solution, and then autoclaving at 150-300 1C. Up to date, the hydrothermal preparation of BT nanoparticles has been investigated extensively [5][6][7][8][9][10][11][12][13][14][15]. The effects of the synthesis temperature, the pH value of the reactive medium, and the Ba/Ti ratio on the particle size and morphology have also been investigated [9][10][11][12], but different results were reported by various researchers.…”