Effects of annealing temperature on structural phase transition and microstructure evolution of hydrothermally synthesized barium titanate nanoparticles

Abstract

Commercial hydrothermally synthesized BaTiO3 powder with a cubic structure was annealed in a temperature range of 650–900 ℃, and the cubic-tetragonal structure transition and microstructure evolution of the powder were investigated in relation to the annealing process. The BaTiO3 powder used had a cubic structure below an annealing temperature of 800 ℃ and a tetragonal structure above 850 ℃. Particle growth occurred under a low activation energy of ~33.2 kJ/mol because of the nanocrystalline size effect, while the crystallite size slightly decreased in the powder with the cubic structure and sharply increased in that with the tetragonal structure. This was because the OH group in the powder with the cubic structure influenced the lattice extension on the particle surface. This stabilized the cubic structure and reduced the crystal ordering, which retarded the crystallite size. When the annealing temperature was increased, the crystallite growth reduced the intrinsic strain and enhanced the tetragonality in the powder with the tetragonal structure as a result of the removal of the OH group.

Effects of annealing on particle size and pore size distribution of hydrothermally synthesized BaTiO3 nanopowders and their grain-growth kinetics during sintering

“…The hydrothermally synthesized BaTiO3 nanopowders with a mean particle size of ∼100 nm, purity of 99.95%, and cubic crystal structure (Shandong Sinocera Functional Material Co., Ltd, China) were synthesize and annealed at 600 °C and 750 °C for 5 h to increase the particle size without transforming the crystal structure from cubic to tetragonal, which is based on empirical research that the phase transition of hydrothermally synthesized BaTiO 3 occurs at annealing temperatures higher than 850 °C [16]. Three powders with different particle sizes were prepared by the annealing process and compressed into a cylindrical shape with a diameter of 6 mm and thickness of 2 mm at 60 MPa for 5 min at room temperature.…”

“…Barium hydroxide is present as barium ions, whereas titania exists as a solid phase that dissolves into the liquid phase to participate in the reaction of equation (1). The hydrothermally synthesized BaTiO 3 powders initially contain H 2 O and OH − , which are eliminated by an annealing process that transforms the crystalline structure from cubic to tetragonal [16]. Notably, the hydrothermal technology has also been used to synthesize BaTiO 3 single crystals and thin films [17,18].…”

A Facile and Eco-Friendly Hydrothermal Synthesis of High Tetragonal Barium Titanate with Uniform and Controllable Particle Size

“…The degree of tetragonal distortion of BT (tetragonality, the ratio of the lattice parameter c to a) caused by the eccentric displacement of titanium atoms is commonly used Materials 2023, 16, 4191 2 of 12 to measure the dielectric properties [13,14]. The higher the ratio of c/a, the higher the dielectric constant of the BT powder [15].…”

“…Typically, a high c/a ratio and suitable particle size are essential to obtain high-performance BT powders. The crystal structure and dielectric properties of BTPs are also affected by their shape, size, and uniformity [16]. Nevertheless, previous studies have shown that the structure of BT powders obtained by traditional hydrothermal methods generally presents the cubic phase or a small amount of tetragonal phase, which is unfavorable for the dielectric properties [17,18].…”