Nano-sized Barium Titanate Powders Research Articles

Usage of Barium Titanate in Fabric Coating and Investigation of Some Properties

In this study, nano-sized barium titanate powder was applied for the first time to polyester woven fabrics by knife coating at three different concentration rates. Some physical (thickness, mass per unit area, bending rigidity, air permeability and tear strength) properties, electromagnetic shielding efficiency and solar (transmittance, reflectance) properties of samples were presented. The samples were also characterized by Fourier transform infrared spectroscopy and scanning electron microscopy. Electromagnetic shielding effectiveness of the fabrics was determined according to the ASTM D4935-10 standard by using a coaxial transmission line measurement technique in the frequency range of 15–3000 MHz. The solar properties were measured according to EN14500 standard using a UV/VIS/NIR spectrophotometer and results were calculated according to EN 410 standard. Results revealed that the electromagnetic shielding effectiveness and solar reflectance property of samples improved with increasing barium titanate concentration.

Research Development of Preparation Technology of BaTiO3 Nano-Power

Barium titanate (BaTiO3) used a strong dielectric materials, piezoelectric materials and ferroelectric materials, which is a kind of important electronic ceramic materials. With the miniaturization of electronic components, miniaturization, thin layer, nanosized barium titanate powder become an inevitable developing trend of barium titanate dielectric ceramics material. Some recent new progress for synthesis of barium titanate at home and abroad are summarized, the commentaries are made on the preparation process about advantages or disadvantages. Meanwhile, the analysis is made on the developing trend. Supercritical fluid extraction method have simple process, high extraction efficiency, no organic solvent residual, products of good quality, no environmental pollution, and so on. Research of BaTiO3nanopower may become an important direction of the field in the future.

Preparation of Nanosized Barium Titanate Powder by a Direct Reactive Precipitation Method

Columnar crystaldendriteequiaxial dendritescolumnar crystalNanosized powder was synthesized by direct-reactive precipitation process using a stoichiometrical mixture of TiCl4, BaCl2 as the reactants while NaOH as precipitant. Under the ratio of Ba to Ti is 1.02, PH=13, three reaction temperature of 70°C, 80°C and 90°C were conducted respectively. Morphology and phase structure of powder were investigated, and the influence of reaction temperature on powder morphology was discussed. The result indicates that synthesized powder is single cubic BaTiO3 and contains no impurities. BaTiO3 powders generally show spherical, and average particle size decreases with increasing reaction temperature. When reaction temperature is 80°C, BaTiO3 powder has best uniformity and dispersivity with the diameter of 80-100nm. The influence of reaction temperature on powder particle size can be attributed to the corporate contribution of nucleation and growth rate. Polyglycol as surface active agent has a significant effect in restraining agglomeration.

Polyethyleneimine surfactant effect on the formation of nano-sized BaTiO 3 powder via a solid state reaction

Barium titanate powder is widely used in multilayer ceramic capacitors (MLCC) because of its’ superior ferroelectric and dielectric properties. Presently, barium titanate powder is mass-produced using a conventional solid state reaction. However, the conflicting literature reports clearly show that the solid state reaction mechanism is not well understood. Synthesizing nano-sized barium titanate powders with less agglomeration using a solid state reaction method at a low calcination temperature has become a hot research topic. This study examines the effect of polyethyleneimine (PEI) surfactant addition on BaTiO 3 formation in a solid sate reaction. XRD, DTA and TEM are used in this investigation. The results indicate that PEI addition can promote BaCO 3 and TiO 2 mixing homogeneity, which enhances the interfacial reaction between BaCO 3 and TiO 2. BaTiO 3 formation can be obtained through the interfacial reaction between BaCO 3 and TiO 2 at the intimate contact between the reactants and Ti +4 ion diffusion along the surfaces or grain boundaries of BaTiO 3 powders, thereby obtaining a single phase BaTiO 3 powder when calcining at low temperatures for a long period.

Dissolution properties of BaTiO3 nanoparticles in aqueous suspensions

Dissolution of barium ion from aqueous suspensions of commercial nano-sized barium titanate powders (BaTiO3) has been studied at various pH values, solids loading, different time intervals and different electrolyte concentrations. Zeta potential measurements at various pH values and Fourier transform infrared spectroscopy study were also carried out to know the surface behaviour. Dissolution of Ba2+ depends on the suspension pH and stirring time period. The iso-electric points were found at 3.4 and 12.2 for as-received BaTiO3 powder and 2.3 for the leached BaTiO3. The Ba2+-leached BaTiO3 suspension retards further leaching of Ba2+ ions at different pH values, which favours the achievement of stable suspension.

Synthesis of Nano-Sized Barium Titanate Powder by Rotary-Hydrothermal Process

Nano-sized BaTiO3 powders with narrow size distribution and the high tetragonality were attempted to synthesize by the rotary-hydrothermal process in water system, using two kinds of commercial anatase-type TiO2 (ST21/ST01) with different particle size and Ba(OH)2. The rotary-hydrothermal syntheses were done with the rotary-speed of 20 revolutions per minute at 523 K for 24 h. Highly- and mono-dispersed BaTiO3 powders were successfully synthesized by applying the rotary-hydrothermal process. For rotary-hydrothermal synthesis, it was found that the average size, tetragonality, and quality of the BaTiO3 particle strongly depended on the particle size of the starting material. In the case of using ST01 as a starting material, BaTiO3 nano-powders mainly composed of coarse-faceted particles (average particle size = ca.100 nm) with the tetragonal phase and very little lattice defects were successfully synthesized.

Hydrothermal Synthesis of Barium Titanate: Effect of Titania Precursor and Calcination Temperature on Phase Transition

Nanosized barium titanate powders were synthesized by a hydrothermal method. The effect of titania precursors on the phase transition of BaTiO3 with respect to Ba/Ti ratio, reaction temperature, reaction time, and calcination temperature was investigated. The synthesized materials were characterized by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. BaTiO3 in pure cubic phase with spherical morphology was observed with a lower calcination temperature, Ba/Ti ratio, reaction temperature, and time. Increase in the tetragonal phase was ascertained in treatments at higher reaction temperature with a longer reaction time. The lattice hydroxyl release is believed to be the reason for tetragonality at high reaction and calcination temperatures. To prepare tetragonal BaTiO3 using HClO4-TiO2, the optimum synthesis conditions viz., Ba/Ti ratio, reaction temperature, and reaction time, are 1.2, 160 °C, and 3 h, respectively, at a calcination temperature of 1150 °C. The reaction time and reaction temperature for the cubic−tetragonal phase transformation of BaTiO3 shifted toward shorter reaction time and lower reaction temperature when TiO2 was synthesized by hydrolysis using HClO4 as the acid catalyst.

Synthesis of Barium Titanate by Hydrothermal Method and Its Formation Mechanisms

The formation of nano-sized barium titanate powders by hydrothermal reaction between barium hydroxide octahydrate and hydrous titania was studied at various temperatures, times and reactant concentrations without mineralizer. FTIR, TGA, SEM, XRF, BET and XRD were used to investigate the effects of temperature, time and concentration on reactivity, particle size, morphology and secondary phase of BaTiO3 powder prepared hydrothermally. The main impurities were BaCO3, TiO2, surface H2O and lattice OH– radical at low conversion while secondary phase such as the lattice hydroxyl radical and trace BaCO3 remained at high conversion. As the temperature and time increased in low concentration reaction below 0.5 M, the maximum conversion could not exceed 98% but the conversion increased with increasing concentration, reaching over 99% above 1.5 M. In addition, concentration of more than 1.5 M was favorable to smaller particle size, better sphericity and Ba/Ti ratio ≒ 1. Kinetic analysis by the Johnson–Mehl–Avrami plot shows hydrothermal reaction progresses through solidification path. Initially, dissolution-precipitation mechanism takes place to form the nuclei of BaTiO3 through fast dissolution of TiO2·xH2O and reaction with Ba2+ ions and then the BaTiO3 crystal begins to grow.

Microwave synthesis of nano-sized barium titanate

Nano-sized barium titanate powders have been synthesized by microwave processing at 2.45 GHz. Using barium titanyl oxalate (BTO) as a precursor, microwave processing was carried out by heating the precursor to a temperature between 600 °C and 750 °C with different heating rates from 10 °C/min to 20 °C/min without isothermal holding. X-ray diffraction analysis indicates that the decomposed product at 680 °C was pure cubic BaTiO 3. The BET specific surface area of barium titanate powder, after microwave heating to 680 °C, was 14.2 ± 0.5 m 2/g, corresponding to an average particle size of 70 nm. This particle size was confirmed by the scanning electron microscopy (SEM). Parallel study shows that the conventional heating in a regular resistance furnace using a similar heating schedule did not result in complete conversion of BTO. This study shows that the microwave processing significantly accelerated the decomposition of barium titanyl oxalate and reduced the temperature of barium titanate nano-powder formation, resulting in nano-sized pure cubic barium titanate powder.

Nano-sized barium titanate powders with tetragonal crystal structure prepared by flame spray pyrolysis

Nano-sized BaTiO 3 powders with regular morphology and tetragonal crystal structure were prepared by flame spray pyrolysis from a spray solution with citric acid. The precursor powders prepared at the low flow rates of fuel gas at 2 and 2.5 L/min had large, hollow, thin wall structures. On the other hand, the precursor powders prepared at a high flow rate of fuel gas at 4 L/min had a dense submicronic structure. Those precursor powders with a hollow, thin wall structure formed a slightly aggregated BaTiO 3 of nanometer-sized primary powders after post-treatment. The slightly aggregated BaTiO 3 became nano-sized powders via a simple milling process. The mean sizes of the powders changed from several tens to 200 nm when post-treatment temperatures changed from 700 to 1000 °C. The BaTiO 3 powders obtained from the citric acid spray solution had tetragonal crystal structure at post-treatment temperature of 1000 °C. Conversely, those BaTiO 3 powders prepared from a spray solution that did not contain citric acid had cubic crystal structures at this same post-treatment temperature.

A Novel, Controlled, and High-Yield Solvothermal Drying Route to Nanosized Barium Titanate Powders

In this report, we describe a novel solvothermal procedure for the synthesis of nanosized particles of barium titanate (BaTiO3). We have been able to synthesize large amounts of nearly uniform sized BaTiO3 nanocrystals in the size range of 5−37 nm. The advantages of our technique over other previously reported hydrothermal/solvothermal approaches are the high yield and the simple but precise control of the size of the particles, which is very conveniently achieved by changing the water content of the reaction mixture in a measured way. The particles are systematically characterized by powder X-ray diffraction (XRD), Raman scattering, scanning electron microscopy (SEM), transmission electron microscopy (TEM), electron diffraction (ED), high-resolution TEM (HRTEM), disc centrifugation, thermogravimetric and differential thermal analyses (TGA-DTA), infrared spectroscopy (IR), and inductively coupled plasma−optical emission spectrometer (ICP-OES). The as-synthesized BaTiO3 nanopowders contain BaCO3 byproduct as well as internal OH- groups and residual solvent species that can be removed by acid washing following heating. However, it is shown that this procedure results in the substantial change of the chemical composition and strong degradation of real microstructure of nanosized BaTiO3 particles.

Preparation and Characterization on Nano-Sized Barium Titanate Powder Doped with Lanthanum by Sol-Gel Process

The nano-sized BaTiO 3:La 3+ powders were prepared by sol-gel process using butyl phthalate, barium acetate and lanthanum oxide as raw material, and these samples were tested by means of TG-DTA, XRD and SEM. The results indicate that with the annealing temperature and the doped concentration rising, the powders' particle sizes will increase and decrease respectively. When annealing temperature is 900 °C and doped concentration is 7%, the phase is cubic without other phases, and the particle size of power is 43.34 nm.

Effects of heat treatment and particle size on the tetragonality of nano-sized barium titanate powder

Although fine BaTiO 3 powders with high tetragonality (= c/ a) are required to increase the volumetric efficiency of a multilayer ceramic capacitor in industry, the tetragonality decreases and disappears below a certain particle size. In order to check the effects of particle size and processing temperature on tetragonality, heat treatment and X-ray diffraction were performed using commercial hydrothermal BaTiO 3 powders after adding different amounts of carbon black. Carbon black was burned out completely up to 600 °C during the heat treatment while acting as an effective particle growth inhibitor even at high temperature like 1100 °C. By changing the amount of carbon black, the synthesis of BaTiO 3 particles having similar size at different processing temperatures was possible. Tetragonality depended linearly on the average particle size up to 330 nm, while showing a saturated value of 1.0105 for larger particles. Tetragonality was not a function of processing temperature for particles heat treated above 950 °C, which implied that the heat treatment above 950 °C was not helpful for the enhancement of tetragonality.

Tetragonality of nano-sized barium titanate powder prepared with growth inhibitors upon heat treatment

Nano-sized barium titanate powders with high dielectric constant are preferred for many reasons in industry, while it is generally known that the dielectric constant is decreasing with the decrease in particle size. In order to enhance the dielectric constant of fine hydrothermal BaTiO 3 powders by eliminating the internal defects, heat treatment at various temperatures is performed. The behavior of tetragonality, an indirect measure of dielectric constant, is investigated as a function of particle size and heat treatment temperature. Growth inhibitors such as carbon black and corn starch are added to minimize the drawbacks of heat treatment such as hard agglomeration and particle growth. Controlling the particle size is possible by using inhibitors, but the efficiency of tetragonality enhancement by heat treatment is relatively low. Explanations for these results are included.

Hydrothermal Synthesis and Structure Characterization of Nanocrystalline Barium Titanate Powders

Nano-sized barium titanate powders were prepared by the high-gravity reactive precipitation (HGRP)-hydrothermal method. The properties and defects of hydrothermal barium titanate crystallites were investigated by TEM, XRD and FTIR. The mean particle size of the hydrothermal barium titanate was about 70 nm with narrow particle size distribution. The crystallite phases and OH defects were focused. The results show that the powders without heat treatment were crystallized as cubic-BaTiO3 and the absence of tetragonal with increasing calcined temperature to 1100°C. The IR results exhibited the OH defect content in the crystallites was to increase the heat treatment temperature and reduced the probability of forming barium vacancies.

Rheological properties of nanosized barium titanate prepared by HGRP for aqueous tape casting

The conditions for the preparation of stable nanosized barium titanate suspensions with high solids content for the production of aqueous tape casting are identified. The rheological behavior of colloidal barium titanate suspension with Ammonium polyacrylate (NH 4-PAA) as a dispersant to aid the powder dispersion has been investigated. Nanosized barium titanate powder was synthesized by a continuous high-gravity reactive preparation (HGRP) technique, and then annealed at 900 °C for 2 h. Measuring the zeta potential, the particle size distributions and ball-milling time, assessed the optimum conditions of the suspension with low viscosity and stability. An isoelectric point (IEP) at pH = 2.8 was found. Particle size distribution tests identified an optimum pH value about 10 and an optimum dispersant addition about 1.2 wt.% (based on the dry powder weight). As the ball-milling time was longer than 8 h, the amount NH 4-PAA adsorbed on the barium titanate reached to saturation. The maximum solid content attained during this work was 45 vol.% at pH of 10, with dispersant addition 1.2 wt.%. High green density value (up to ∼55.4% of the theoretical density) in BaTiO 3 sheet was achieved with a solid content 40 vol.%. After sintering at 1200 °C for 2 h a final density of 95% is reached.

Nanosized Barium Titanate Powder by Mechanical Activation

Mechanical activation, without any additional heat treatment, is used to trigger the formation of a perovskite BaTiO3 phase in an oxide matrix that consists of BaO and TiO2 in a nitrogen atmosphere. The resulting BaTiO3 powder exhibits a well‐established nanocrystalline structure, as indicated by phase analysis using X‐ray diffractometry. A crystallite size of ∼14 nm is calculated, based on the half‐width of the BaTiO3 (110) peak, using the Scherrer equation, and an average particle size of 20–30 nm is observed using transmission electron microscopy for the activation‐derived BaTiO3 powder.

Synthesis and Sintering of Nanocrystalline Barium Titanate Powder under Nonisothermal Conditions. Part V. Nonisothermal Sintering of Barium Titanate Powders of Different Dispersion

A comparative study has been made of the processes involved in the consolidation of nanosized barium titanate powders by nonisothermal sintering at a linear heating rate, by rate-controlled sintering, and high-pressure sintering (up to 5 GPa). The use of linear heating and high-pressure has been found to be ineffective for obtaining nonporous ceramics (residual porosity of about 2%) and for miniziming grain growth. The application of external pressure does not prevent coalescent grain growth controlled by surface diffusion. When rate-controlled sintering is employed a densification/grain growth optimum can be attained with a relative density of 99.9% of the theoretical value and a grain size of about 100 nm.

Suppression of Exaggerated Grain Growth During Sintering of Nano-Sized Barium Titanate Powders

AbstractRate controlled sintering (RCS) was used to sinter nano-sized BaTiO3 particles. A distinct shift in temperature slope above 1150-1200°C during RCS implied a change in sintering mechanism, and a corresponding exaggerated grain growth (grain size ~40-50 μm). By suppression of the exaggerated grain growth by firing a specimen packed in BaCO3, these phenomena were shown to be the result of a shift in phase equilibria from the volatilization of BaO from BaTiO3; the eutectic liquid which formed permitted rapid grain growth by a dissolution and precipitation process.