Effect of solvents on the morphology and structure of barium titanate synthesized by a one-step hydrothermal method

Tetragonal barium titanate was synthesized from barium hydroxide octahydrate and titanium tetrachloride through a simple one-step hydrothermal method.The effect of different solvents on the crystal structure and morphology of barium titanate nanoparticles during the hy-drothermal process was investigated.Except for ethylene glycol/water solvent,impurity-free barium titanate was synthesized in pure water,methanol/water,ethanol/water,and isopropyl alcohol/water mixed solvents.Compared with other alcohols,ethanol promotes the formation of a tetragonal structure.In addition,characterization studies confirm that particles synthesized in methanol/water,ethanol/water,and isopropyl al-cohol/water mixed solvents are smaller in size than those synthesized in pure water.In the case of alcohol-containing solvents,the particle size decreases in the order of isopropanol,ethanol,and methanol.Among all the media used in this study,ethanol/water is considered the optimum reaction media for barium titanate with high tetragonality(defined as the ratio of two lattice parameters c and a,c/a=1.0088)and small aver-age particle size(82 nm),which indicates its great application potential in multilayer ceramic capacitors.

Dopant Behaviours of Sm_2O_3 on Microstructure and Properties of Barium Zirconium Titanate Ceramics

The effect of Sm 2O 3 dopant on the sintering characteristics and dielectric properties of barium zirconium titanate ceramics (BaZr x Ti 1- x O 3) was investigated. It is shown that trace amount of Sm 2O 3 can greatly affect the grain growth and densification of barium zirconium titanate ceramics during sintering. At the same time, the dielectric peak at high temperature shifts to lower temperature and that at low temperature shifts to higher temperature. The two dielectric peaks overlap with each other when the Sm 2O 3 dopant content varies from 0 25% to 1%, and the maximum relative dielectric constant is greatly enhanced. These effects may be attributed to the substitution actions of the rare earth element in perovskite lattice. At the doping content of 0 75%, the dielectric constant maximum of 23570 can be obtained. By adopting some proper additives, an excellent Y5V dielective material is obtained, and the room temperature properties are as follows: relative dielectric constant ε RT ≥23,000, dielectric loss tgδ≤0 0075 and the breakdown strength under alternating field E b≥5 kV·mm -1 .

Optimized growth and dielectric properties of barium titanate thin films on polycrystalline Ni foils

Barium titanate（BTO） thin films were deposited on polycrystalline Ni foils by using the polymer assisted deposition（PAD） technique.The growth conditions including ambient and annealing temperatures were carefully optimized based on thermal dynamic analysis to control the oxidation processing and interdiffusion.Crystal structures,surface morphologies,and dielectric performance were examined and compared for BTO thin films annealed under different temperatures.Correlations between the fabrication conditions,microstructures,and dielectric properties were discussed.BTO thin films fabricated under the optimized conditions show good crystalline structure and promising dielectric properties with εr～ 400 and tan δ 〈 0.025 at 100 kHz.The data demonstrate that BTO films grown on polycrystalline Ni substrates by PAD are promising in device applications.

Effects of Dysprosium Oxide Doping on Microstructure and Properties of Barium Titanate Ceramic

Different amounts of dysprosium oxide were incorporated into barium titanate powders synthesized by hydrothermal method. Relations of substitution behaviors and lattice parameters with solid-solubility were studied. Furthermore, the influences of dysprosium oxide doping fraction on grain size and dielectric properties of barium titanate ceramic, including dielectric constant and breakdown electric field strength , were investigated via scanning electron microscope, X-ray diffraction and electric property tester. The results show that dysprosium oxide can restrain abnormal grain growth during sintering and that fine-grained and high density of barium titanate ceramic can result in excellent dielectric properties. As mass fraction of dysprosium oxide is 0.6%, the lattice parameters of grain increase to the maximum because of the lowest vacancy concentration. The electric property parameters are cited as following： dielectric constant （25 ℃ ） reaches 4100, the change in relative dielectric constant with temperature is - 10% to 10% within the range of - 15 - 100 ℃, breakdown electric field strength （alternating current） achieves 3.2 kV·mm^-1, which can be used in manufacturing high voltage ceramic capacitors

PREPARATION OF HIGH-PURITY AND NANOMETER-SCALE BARIUM TITANATE POWDERS

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Barium titanate ceramic inks for continuous ink-jet printing synthesized by mechanical mixing and sol-gel methods

Ink-jet printing of ceramic thick films is one of low cost on-site ceramic pattern fabrication methods.It is necessary to investigate the rheological behaviour of ceramic inks and drying behaviour of droplets.Two kinds of BaTiO3 ceramic inks were prepared by mechanical mixing and sol-gel methods,respectively.The effect of preparation parameters,such as quantity of polyacrylic acid(PAA)and solid content,on physicochemical and rheologic properties of the ceramic inks was investigated.The results show that they satisfy the requirements of continuous ink-jet printing.The appearances of printed dots and single printed layers were observed by SEM.The SEM images indicate that dots printed with mixing method ink are in ring shape,and dots printed with sol-gel method ink are in pancake shape,so the printed layer surface with the latter ink is smoother.The causes of these phenomena were discussed.

Modulating the Selectivity of Photocatalytic CO_(2)Reduction in Barium Titanate by Introducing Oxygen Vacancies

Artifi cial photosynthetic reduction of CO_(2) into valuable chemicals is one of the most promising approaches to solve the energy crisis and decreasing atmospheric CO_(2) emissions.However,the poor selectivity accompanied by the low activity of photocatalysts limits the development of photocatalytic CO_(2) reduction.Herein,inspired by the use of oxygen vacancy engi-neering to promote the adsorption and activation of CO_(2) molecules,we introduced oxygen vacancies in the representative barium titanate(BaTiO 3)photocatalyst for photocatalytic CO_(2) reduction.We found that oxygen vacancies brought signifi cant diff erences in the CO_(2) photoreduction activity and selectivity of BaTiO 3.The intrinsic BaTiO 3 showed a low photocatalytic activity with the dominant product of CO,whereas BaTiO 3 with oxygen vacancies exhibited a tenfold improvement in photocatalytic activity,with a high selectivity of~90%to CH 4.We propose that the presence of oxygen vacancies promotes CO_(2) and H 2 O adsorption onto the BaTiO 3 surface and also improves the separation and transfer of photogenerated carriers,thereby boosting the photocatalytic CO_(2) reduction to CH 4.This work highlights the essential role of oxygen vacancies in tuning the selectivity of photocatalytic reduction of CO_(2) into valuable chemicals.

Low Temperature One-Step Synthesis of Barium Titanate:Thermodynamic Modeling and Experimental Synthesis

A thermodynamic model has been developed to determine the reaction conditions favoring low temperature direct synthesis of barium titanate (BaTiO3). The method utilizes standard-state thermodynamic data for solid and aqueous species and a Debye-Hǔckel coefficients model to represent solution nonideality. The method has been used to generate phase stability diagrams that indicate the ranges of pH and reagent concentrations, for which various species predominate in the system at a given temperature. Also, yield diagrams have been constructed that indicate the concentration, pH and temperature conditions for which different yields of crystalline BaTiO3 can be obtained. The stability and yield diagrams have been used to predict the optimum synthesis conditions (e.g.,reagent concentrations, pH and temperature). Subsequently, these predictions have been experimentally verified.As a result, phase-pure perovskite BaTiO3 has been obtained at temperature ranging from 55 to 85℃ using BaCl2,TiCl4 as a source for Ba and Ti. and NaOH as a orecioitator.

Low Temperature One Step Synthesis of Barium Titanate: Particle Formation Mechanism and Large-scale Synthesis

The formation of BaTiO3 nanoparticles via the reaction of BaCl2, TiCl4 and NaOH in aqueous solution has been systematically studied. The formation of BaTiO3 from the ionic precursors has been elucidated to be a very rapid process, occurring at temperature higher than 60℃. Furthermore, the particle size could be controlled by the proper selection of the synthesis conditions (e.g. reactant concentration of 0.5—1.0mol·L-1, temperature of 80— 95℃ and pH≥13). A two-step precipitation mechanism was proposed. The first stage of the synthesis involved the formation of amorphous Ti-rich gel phase. The second stage of the synthesis was the reaction between the amor-phous phase and the solution-based Ba2+ ions, which led to the crystallization of BaTiO3. Based on the particle for-mation mechanism, a novel method, high gravity reactive precipitation, was proposed and used to mass production of BaTiO3 of average particle size of about 60 nm and with narrow particle size distribution. Because it could break up the amorphous Ti-rich gel into small pieces, intensify mass transfer, promote the reaction rate of amorphous Ti-rich gel with Ba2+ ions.

Electro-rheological Effect of Barium Titanate Particles Coated with Urea and Suspended in Methyl Silicone Oil

Barium titanate nano-powders were synthesized under defined conditions. The surface of these particles was successfully modified by coating with urea. The characteristics of these composite particles were studied by X-ray diffraction,transmission electron microscopy (TEM) and Fourier transform infrared spectroscopy. The electro-rheological (ER) effects of these particles suspended in methyl-silicone oil were measured. The particle,methyl-silicon oil ratio was 30%-35% weight percent. The experimental results indicate that these ER particles exhibit a remarkable ER effect. The ER fluid shows Bingham characteristics and the static shearing stress increases with an increase of the electric field strength. The highest static shearing stress under a 4 MV/m electric field is 13.2 kPa at room temperature,an increase of about 8.7 kPa compared to untreated BaTiO(C2O4)2 powders.

Properties of composition sinter prepared from fibrous barium titanate and nanometer zirconia

Fibrous Batium Titanate particles, 30 50 μm long, prepared by a hydrothermal reaction, and the monoclinic phase and nanometer Zirconia, 11.6 nm long were prepared by citric acid reaction respectively. Then, the two were composite sintered to produce a new functional material by making full use of crystal axis orientation of fibers and the activity of nanometer powder. The analydid of composition and microstructure of the new material in terms of XRD and SEM. shows that the solid solution was formed between fibers and nanometer powder, and the distance between lattice (d value) of Barium Titanate changed. But the crystal axis orientations of fibers remain unchanged.

Preparation and characterization of barium strontium titanate/silicon nanoporous pillar array composite thin films by a sol-gel method

Barium strontium titanate （Ba0.5Sr0.5TiO3, BST）/silicon nanoporous pillar array （Si-NPA） thin films were prepared by a spin-coating/annealing technique based on Si-NPA with micro/nano-structure. Both the isomer conversion of acetylacetone and the network structure combined by enol and Ti-alkoxide facilitate the formation of the BST sol and the subsequent crystallization. Before the perovskite BST begins to form, the intermediate phase （Ba, Sr）Ti2OsCO3 is found. The boundary between BST and Si-NPA is of clarity and little interface diffusion, disclosing that Si-NPA is an ideal template substrate in the preparation of multifunctional composite films.

HYBRID AND CHARACTERISTIC OF POLYANILINEBARIUM TITANATE NANOCOMPOSITE PARTICLES

Polyaniline-barium titanate (PAn-Ba-TiO3) ultrafine composite particles were prepared by the oxidative polymerization of aniline with H2O2 while barium titanate nanoparticles were synthesized with a sol-gel method. The infrared spectrogram shows that the polymerization of PAn in the hybrid process of PAn-BaTiO3 is similar with the polymeric process of pure aniline, and there is interaction of PAn and BaTiO3 in the PAn-Ba-TiO3. SEM and TEM results show that the average diameter of the composite particles is 1.50μm and the diameters of BaTiO3 nanoparticles are 5 - 15 nm in the composite particle. The electrical conductivity of the ultrafine com-posite particles is transformable from 10°to 10-11S/cm by equilibrium doping or dedoping method using various concentration of HCl or NaOH solutions.

Characterization and growth dynamics of barium titanate crystallite on nanometer scale

Barium titanate powder on nanometer scale was synthesized by means of co-precipitation. The thermal mass loss, crystal grain growth and phase transition of the barium titanate nanometer powder were investigated by TG (Thermogravimetric)-DTA (Differential scanning calorimetric) and XRD (X-ray powder diffractometer) at different heat treatment temperatures. The results show that amorphous barium titanate powder can transfer into tetragonal symmetry structure after heat treatment. When the heat treatment temperature is below 900℃, the grains grow rapidly because the activation energy at low temperature is greatly less than that at high temperature. By controlling the heat treatment temperature, the optimization of the barium titanate crystallite size and formation of tetragonal phase can be realized.

Performance Evaluation of Rectangular Microstrip Patch Antennas Loaded with Plastic and Barium-Titanate Substrates at GSM 1800 MHz Band

In this paper, the resonance and radiation characteristics of patch antennas fabricated with two different types of dielectric substrates have been investigated and compared at GSM 1800 MHz band. At first, the above-stated characteristics of a patch antenna loaded with conventional plastic substrate have been investigated. Later a high permittivity dielectric material (barium titanate) has been used as the antenna substrate. The main goal here is to reduce the antenna size with a high permittivity dielectric material and then to compare its resonance and radiation performance with the earlier low permittivity substrate loaded prototype. It is found that with the use of high permittivity substrate the antenna volume gets smaller (about 6% of the plastic substrate prototype) although the gain decreases by around 2.5 dB.

Structural and Dielectric Properties of Sn Doped Barium Magnesuim Zirconium Titanate Perovskite Ceramics

Perovskite type ceramics (Ba0.9Mg0.1)(SnxZr0.4-xTi0.6)O3 (with x = 0.01, 0.02, 0.03 and 0.04) relaxor composition prepared through solid state reaction route and calcinated at temperature is 1150°C for 5 hrs with intermediate mixing. The room temperature XRD study suggests that all the samples have the single phase cubic symmetry with space group pm 3 m. The pellets were sintered at 1500°C for 4 hrs. Scanning Electron Microscope (SEM) observations revealed enhanced micro structural uniformity and retarded grain growth with decreasing Sn content. The dielectric measurements at constant frequency show that dielectric constant increases with Sn content. Loss factor and dielectric constant decreased with increasing frequency but at very high frequencies it was independent.

An Investigation of PLD-Deposited Barium Strontium Titanate (Ba_xSr_1-xTiO₃) Thin Film Optical Properties

Reflectance and transmittance parameters of pulsed laser deposited barium strontium titanate (BST) were investigated using spectrophotometric methods. Three stoichiometries consisting of BaxSr1-xTiO3 (x = 0.30, 0.40, 0.50) were deposited on glass substrates using oxygen partial pressures of 1.3 Pa ± 0.13 Pa at 500oC. Subsequently, the measured optical parameters were employed to determine the refractive index (n), extinction coefficient (k), optical conductivity (σ), absorption coefficient (α) and optical bandgap (Eg) using swept spectra in the ultraviolet, visible and near-infrared range (200 nm - 1100 nm) as these have not been reported in the literature. The calculated parameters for Ba0.4Sr0.6TiO3 are reported in this experimental work. Minimal differences in the transmittance have been observed at the visible band edges when comparing each stoichiometry. Sharp cutoffs were observed at the bands edges and strong absorbance in the 200 nm - 300 nm band as attributed to the crystal structure based upon the oxygen partial pressure during the deposition process.

Synthesis and characterization of highly-ordered barium-strontium titanate nanotube arrays fabricated by sol-gel method

Highly uniformed barium-strontium titanate nanotube arrays were fabricated using a porous anodic aluminum oxide template from a barium-strontium titanate sol-gel solution. Electron microscope results showed that nanotubes with uniform length and diameter were obtained. The diameters and lengths of these nanotubes were dependent on the pore diameter and the thickness of the applied anodic aluminum oxide template. High resolution transmission electron microscopy and the selected-area electron diffraction pattern investigations demonstrated the perovskite structure and the polycrystalline of the fabricated barium-strontium titanate nanotubes. The characterization of the electrical and dielectric properties had also been made. Compared to thin film material, the intrinsic leakage current density is almost the same. Besides, at 30 ℃ the dielectric constant and dielectric loss of the fabricated nanotube is 80 and 0.027 at 1 MHz respectively.

Preparation and characterization of nanometer-sized barium titanate powder by complex-precursor method

A new complex-precursor method was proposed to prepare nanometer-sized BaTiO3 powder. Firstly,Ti2O(O2)2(ta)24-complex ions were prepared by the reaction of H2O2,Ti4+ and ta3-(ta=C6H6O6N3-) with a desirable amount of surface active agent,and then the Ba2Ti2O(O2)2(ta)2·2H2O precursor was obtained by reaction between Ti2O(O2)2(ta)24-and Ba2+. Finally,the precursor was annealed at 800 ℃ for 2 h to obtain BaTiO3 powder. The morphology,the particle size distribution,the purity and the molar ratio of Ba to Ti of BaTiO3 powder were investigated systematically by TEM,XRD,IR,Raman and chemical analysis,respectively. The results show that the BaTiO3 powders with the grain size of about 40 nm have a tetragonal crystalline structure at room temperature and a spherical morphology.

Enhancing energy storage density of poly(arylene ether nitrile)via incorporating modified barium titanate nanorods and hotstretching

Dielectric energy storage materials that are extensively employed in capacitors and other electronic devices have attracted increasing attentions amid the rapid progress of electronic technology.However,the commercialized polymeric and ceramic dielectric materials characterized by low energy storage density face numerous limitations in practical applications.In this study,we report the simultaneous enhancement of dielectric properties of poly(arylene ether nitrile)(PEN)through the incorporating of sulfonated PEN(SPEN)modified barium titanate nanorods(BTNR)(SPEN@BTNR)and hot-stretching.BTNR is synthesized using a two-step hydrothermal method,aminated with KH550,and then reacted with SPEN to form the cladding-modified SPEN@BTNR.Due to the intrinsic high permittivity of barium titanate(BT)and enhanced compatibility between SPEN@BTNR and PEN stemming from the cladding of SPEN,the dielectric constant and breakdown strength of SPEN@BTNR/PEN composite are as high as 14.0 at 103 Hz and 198.1 kV/mm at the doping amount of 15 wt.%,respectively.As a result,the energy storage density of SPEN@BTNR/PEN is increased to 2.43 J/cm^(3),compared with that of 0.82 J/cm^(3)for PEN.In addition,derived from the rearrangement of SPEN@BTNR and orientation of PEN after hot-stretching,the dielectric constant and breakdown strength of SPEN@BTNR/PEN with 15 wt.%fillers are further enhanced to 17.1 and 204.8 kV/mm,respectively,resulting in an energy storage density of 3.36 J/cm^(3).The boosting of energy storage density up to 310%provides a new idea for improving the performances of dielectric energy storage materials.