Synthesis Of Barium Titanate Powders Research Articles

Methods for the synthesis of barium titanate as a component of functional dielectric ceramics

Objectives. To examine the general principles and recent advances in the synthesis of high-purity and high-homogeneity barium titanate powders in the manufacture of electronic components.Results. The main publications regarding the synthesis of barium titanate powder, including the works of recent years, were analyzed. The technological advantages and disadvantages of various synthesis methods were identified. Groups of methods based on solid-state interaction of reagents and methods of “wet chemistry” were also considered. The possibilities of producing barium titanate particles of non-isometric shapes for creating textured ceramics were discussed separately.Conclusions. Barium titanate is a well-known ferroelectric with a high dielectric constant and low dielectric loss. It is used as a component in ceramic electronic products, for example, capacitors, memory devices, optoelectronic devices, and piezoelectric transducers. The possibilities of producing functional ceramics based on barium titanate powder largely depend on its state and morphological characteristics, determined during the synthesis stage. The most important factors affecting the functional characteristics of ceramics are the purity and morphology of the powder raw materials used.

Low Temperature Synthesis of Barium Titanate Powder by a Modified Sol-Gel Method

Barium titanate (BT) is one of the most important lead-free ferroelectric materials with perovskite crystal structure and high dielectric constant. Among synthesis techniques of BT, sol-gel processing has attracted considerable interest due to the control of composition, surface morphology engineering, low temperature processing, and low equipment cost. In this research, nanocrystalline BT powders were prepared by a modified sol-gel technique. Acetic acid and water were used as solvents. The samples were heat treated at various temperatures, times, and rates for investigating the effect of heat treatment parameters on formation of single perovskite crystalline phase. According to the results of X-ray diffraction analysis, highly pure BT powder with minimum secondary phases (Magneli) was obtained after calcination at 650 °C for 1 h with the rate of 10 °C/min. The grain size and morphology of BT powders were obtained by field emission scanning electron microscopy which indicated the size of about 60 nm.

Microwave hydrothermal synthesis of barium titanate powders

Microwave hydrothermal method was used to synthesize BaTiO3 powders. XRD, SEM and EDS were used to characterize the obtained BaTiO3 powder. The obtained BaTiO3 powder is monosized distribution equi-axed particles of size 150 nm. The BaTiO3 powder of Ba/Ti ratio close to 1 can be obtained at ratio 1.6 of [Ba]/[Ti] in precursor in 2.0 M [NaOH] solution. The results showed that with the increase the reaction time, the grain size of BaTiO3 powder increases. There is an optimal reaction temperature 80 °C, at which the best crystallization is attained.

Synthesis of barium titanate powders by aerosol pyrolysis of a Pechini-type precursor solution

A Pechini-type precursor system, utilizing Ba-nitrate and Ti-isopropoxide with citric acid (CA) and ethylene glycol (EG), has been investigated for the synthesis of BaTiO3 powders using aerosol pyrolysis. Powder produced at 350 °C in the aerosol process had subsequent thermal decomposition (TGA/DTA) behavior that was similar to that reported for the barium titanyl citrate complex BaTi(C6H6O7)3·xH2O, indicating that the short process time and rapid droplet evaporation limit substantial polyester network development in the aerosol process. Crystalline phase development proceeded rapidly at reactor temperatures between 600 and 700 °C. Small amounts of the intermediate phases Ba2Ti2O5CO3, BaCO3 and Ba(NO3)2,were present as impurities in powder produced at 700 °C, and phase-pure BaTiO3 was produced at temperatures above 800 °C. In contrast, a precursor solution utilizing acetic acid as peptizing agent led to a significant amount of nonstoichiometric BaTi2O5, highlighting the importance of the multidentate complexation of citric acid. Dimpled or slightly collapsed hollow particles were typically produced using the Pechini-type precursor. It was demonstrated that the polymeric additives polyethylene glycol and methylcellulose could be used to alter particle morphology without impacting product phase-purity.

Synthesis of barium titanate powders and coatings by treatment of TiO2 with molten mixtures of Ba(NO3)2, KNO3 and KOH

Synthesis of barium titanate powders and coatings by treatment of TiO2 with molten mixtures of Ba(NO3)2, KNO3 and KOH

Synthesis of barium titanate powders and coatings by treatment of TiO 2 with molten mixtures of Ba(NO 3) 2, KNO 3 and KOH

The possibility to synthesize BaTiO 3, SrTiO 3 and CaTiO 3 by treatment of TiO 2 powders with molten mixtures of R(NO 3) 2–KNO 3–KOH is presented. The influence of time of treatment, temperature and KOH contents in the melt on the yield of BaTiO 3, was investigated. The process mechanism taking place in the analyzed systems is discussed. It is shown that the synthesis includes the stages of TiO 2 dissolution, Lux–Flood acidic–basic transformation of TiO 2 fragments into titanate ions via interaction with O 2− and crystallization of barium titanate. It was also found that barium titanate coatings can be formed by direct treatment of TiO 2 films on solid substrates under the same experimental conditions.

New evidence of a dissolution–precipitation mechanism in hydrothermal synthesis of barium titanate powders

Accomplished by varying the precursors of BaTiO 3 powders as hydrothermal preparation in the strong basic solution, this paper has observed the following new pieces of evidence of a mechanism by dissolution–precipitation: (1) SEM observations of the TiO 2 powders of fore-and-aft hydrothermal reaction, using TiCl 4 and NaOH as precursors, show a dissolution process; (2) TEM observations of incompletely reacted powders, using TiCl 4, BaCl 2 and NaOH as precursors, show that the homogeneous nucleation occurs instead of heterogeneous nucleation; (3) uniform BaTiO 3 powders with the average particle size of 0.5 μm could be quickly prepared by the hydrothermal method, using BaTiO 3 powders prepared by oxalate coprecipitation method as precursor. These three experimental observations provide new strong evidence of dissolution–precipitation as the hydrothermal preparation mechanism of BaTiO 3 powders in the strong basic solution.

Synthesis of Barium Titanate Powders by Low-Temperature Aqueous Synthesis Using a New Segmented Flow Tubular Reactor

Reference LTP-CONF-2002-009View record in Web of Science Record created on 2005-01-12, modified on 2017-05-10

Evidence of a dissolution–precipitation mechanism in hydrothermal synthesis of barium titanate powders

In our study of the system barium hydroxide-titanium tetraisopropoxide–water–isopropanol between 85 and 150 °C, we have observed the following evidence of a mechanism by dissolution-precipitation: (1) when varying the water/isopropanol ratio in synthesis at 150 °C, the grain size of barium titanate decreases when the amount of alcohol increases, i.e. when the solubility of the precursors decreases; (2) TEM observations of incompletely reacted powders showed that the grains are either amorphous or entirely crystalline BaTiO 3, which means that homogeneous nucleation and growth is occurring instead of heterogeneous nucleation; (3) high resolution TEM observations of fully reacted powders revealed the presence of necks between particles. These three experimental observations in the same reaction system provide strong evidence of dissolution-precipitation as the primary reaction mechanism.

Preparation and Characterization of Nano-structured Ceramic Powders Synthesized by Emulsion Combustion Method

The emulsion combustion method (ECM), a novel powder production process, was originally developed to synthesize nano-structured metal-oxide powders. Metal ions in the aqueous droplets were rapidly oxidized by the combustion of the surrounding flammable liquid. The ECM achieved a small reaction field and a short reaction period to fabricate the submicron-sized hollow ceramic particles with extremely thin wall and chemically homogeneous ceramic powder. Alumina, zirconia, zirconia–ceria solid solutions and barium titanate were synthesized by the ECM process. Alumina and zirconia powders were characterized to be metastable in crystalline phase and hollow structure. The wall thickness of alumina was about 10 nm. The zirconia–ceria powders were found to be single-phase solid solutions for a wide composition range. These powders were characterized as equiaxed-shape, submicron-sized chemically homogeneous materials. The powder formation mechanism was investigated through the synthesis of barium titanate powder with different metal sources.

Synthesis and sintering of nanocrystalline barium titanate powder under nonisothermal conditions. I. Control of dispersity of barium titanate during its synthesis from barium titanyl oxalate

We have studied the process of synthesis of barium titanate powder from barium titanyl oxalate precursor under nonisothermal conditions. We studied the effect of the heating rate on the specific surface area of the powder. We have established the advantages of nonisothermal conditions compared with isothermal conditions, especially the possibility of flexible control over the barium titanate grain size.

Sol–gel synthesis of barium titanate powders of various compositions

Sol–gel synthesis of barium titanate powders of various compositions

Sol-Gel Synthesis of Barium Titanate Powders Using Barium Acetate and Titanium(IV) Isopropoxide

A sol-gel process for low-temperature preparation of BaTiO{sub 3} powders is described. Chemical polymerization between barium acetate and titanium(IV) isopropoxide leads to the formation of barium titanate gels. After suitable drying and calcination treatments, the barium titanate gels were converted to BaTiO{sub 3} powders. The barium titanate gels and powders were characterized by TGA, DTA, and XRD. The results of these analyses indicate that it is possible to obtain stoichiometric (Ba/Ti = 0.99), homogeneous, high-purity BaTiO{sub 3} powders using relatively inexpensive barium acetate as a starting material.