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Barium Titanate (barium + titanate)
Selected AbstractsTexture Development in Barium Titanate and PMN,PT Using Hexabarium 17-Titanate HeterotemplatesINTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 1 2005Toshio Kimura Bulk BaTiO3 ceramics with ,111,-texture have been prepared by the modified templated grain growth method, using platelike Ba6Ti17O40 particles as templates, and the mechanism of texture development is examined. The Ba6Ti17O40 particles induce the abnormal growth of BaTiO3 grains, and a structure similarity between {001} of Ba6Ti17O40 and {111} of BaTiO3 gives ,111,-texture to abnormally grown BaTiO3 grains. Thus, the ,111,-texture develops in the BaTiO3 matrix. The use of platelike Ba6Ti17O40 particles has been extended to a 0.65Pb(Mg1/3Nb2/3)O3,0.35PbTiO3 matrix, but the matrix phase is decomposed by extensive chemical reactions between the matrix and template phases. [source] Modified Phase Diagram for the Barium Oxide,Titanium Dioxide System for the Ferroelectric Barium TitanateJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 8 2007Soonil Lee The ferroelectric phase transition behavior in BaTiO3 was investigated for various annealing times, temperatures, and Ba/Ti ratios by means of a differential scanning calorimeter. Coupling these observations with powder X-ray diffraction and transmission electron microscopy allowed new insights into the barium oxide (BaO),titanium dioxide (TiO2) phase diagram. The transition temperature was varied systematically with the Ba/Ti ratio at annealing temperatures from 1200° to 1400°C in air. The transition temperature decreased with increasing concentrations of BaO and TiO2 partial Schottky defects, and showed a discontinuous change at the phase boundaries. Beyond the solubility region, two peritectoid reactions were confirmed and revised; first around 1150°C for Ba1.054Ti0.946O2.946,Ba2TiO4+BaTiO3 and second 1250°C for BaTi2O5,Ba6Ti17O40+BaTiO3, respectively. All other regimes of the BaO,TiO2 were found to be consistent with the reported diagrams in the literature. [source] Effect of the Liquid-Phase Characteristic on the Microstructures and Dielectric Properties of Donor- (Niobium) and Acceptor- (Magnesium) Doped Barium TitanateJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 1 2003Seok-Hyun Yoon Changes in the microstructure and dielectric properties with the variation of the donor/acceptor ratio in BaTiO3 ceramics were investigated. In donor-rich specimens, a liquid that appeared during sintering did not penetrate into grain boundaries. However, in the acceptor-rich specimens, the grains were separated by a liquid film during sintering. The much higher mobility of the liquid film than that of the grain boundaries was suggested to cause extensive grain growth in acceptor-rich BaTiO3. The macroscopic homogenization of dopants because of grain growth in acceptor-rich specimens resulted in changes in the dielectric properties. [source] Hydrothermal Synthesis of Tetragonal Barium Titanate from Barium Chloride and Titanium Tetrachloride under Moderate ConditionsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 3 2002Huarui Xu Tetragonal BaTiO3powders were prepared hydrothermally at 240°C, in only 12 h, using BaCl2·2H2O and TiCl4, which are rather easy to manipulate. Characterization via X-ray diffractometry, scanning electron microscopy, Brunauer,Emmett,Teller analysis, and differential scanning calorimetry confirmed that increasing the NaOH excess concentration (from 0.5M to 2.0M) and decreasing the initial TiCl4concentration (from 0.625M to 0.15M) promotes the formation of tetragonal BaTiO3powders. After reaction, the powders were proved to be phase-pure BaTiO3, with no impurities, such as Cl, and CO32,. [source] Revisit to the Origin of Grain Growth Anomaly in Yttria-Doped Barium TitanateJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 8 2001Jung-Kun Lee In this study, the effect of atmosphere during calcining and sintering of Y2O3 -doped BaTiO3 was investigated to reveal the origin of the anomaly of grain growth and conductivity as a function of Y2O3 content. Samples with various atmospheric histories were prepared. Microstructural and electrical variations were observed using SEM, dielectric (,r vs T) and thermopower measuring techniques, and impedance spectroscopy. An abrupt decrease in grain growth and a transition from semiconducting to insulating behavior were observed when the Y2O3 concentration exceeded 0.3 mol% and the samples were heat-treated in an O2 atmosphere. In contrast, the samples treated under N2+ 5% H2 atmosphere revealed neither grain growth anomaly nor conductivity anomaly even though the Y2O3 concentration was much greater than 3 mol%. The undoped BaTiO3 samples also demonstrated increased average grain size with increased oxygen partial pressure. Therefore, it was suggested that the grain growth anomaly did not result from the formation of cation vacancies V,Ba or V,,Ti. To investigate the origin of the grain growth anomaly, the Curie temperature, concentration of free electrons, and impedance spectra were measured. The grain growth anomaly and conductivity anomaly were associated with abrupt changes in all the measurements. These abrupt changes could be explained by the partial incorporation of donor dopants. Consequently, the origin of the anomaly in the microstructure and electrical properties are discussed in terms of grain-boundary segregation of the donor dopant. [source] Positive Temperature Coefficient of Resistivity Effect in Highly Donor,Doped Barium TitanateJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 6 2001Darko Makovec BaTiO3 ceramics doped with different La concentrations (0,12 mol%) were prepared by sintering under the reducing conditions of a nitrogen atmosphere containing 1% hydrogen. The critical donor concentration that causes blocking of the exaggerated grain growth was observed to be ,10 mol% La. The samples, which were semiconducting after sintering under reducing conditions, were subsequently reoxidized by annealing in air to induce the positive temperature coefficient of resistivity (PTCR) effect. After reoxidation at 1150°C a noticeable PTCR effect was observed in the samples doped with La concentrations as high as 2.5 mol%. The room-temperature resistivity after reoxidation was found to increase with increasing donor concentration due to an increase in the thickness of the insulating layers at the grain boundaries. TEM analysis showed that reoxidation of the samples caused precipitation of the Ti-rich compound Ba6Ti17O40 inside the doped BaTiO3 -matrix grains. [source] Effect of Silver on the Sintering and Grain-Growth Behavior of Barium TitanateJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 12 2000Chin-Yi Chen Silver and its alloys frequently are used as electrode material for BaTiO3 -based dielectrics. In the present study, a small amount of fine silver particles have been intimately mixed with BaTiO3 powder. The sintering and grain-growth behavior of the silver-doped BaTiO3 in air are investigated. The solubility of silver in BaTiO3, as revealed by lattice-parameter measurement, electrical measurement, and electron probe microanalysis, is <300 ppm. The densification of BaTiO3 is slowed slightly by the addition of silver inclusions. However, the presence of a small amount (<0.3 wt%) of silver increases the amount and size of abnormal grains. When the silver content is >0.3 wt%, the grain growth of BaTiO3 then is prohibited by the silver inclusions. [source] Role of Length Scale on Pressure Increase and Yield of Poly(vinyl butyral),Barium Titanate,Platinum Multilayer Ceramic Capacitors during Binder BurnoutJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 11 2000Leo C.-K. The binder-burnout kinetics of poly(vinyl) butyral from BaTiO3 multilayer ceramic capacitors with platinum metal electrodes were analyzed by combining thermogravimetric analysis with infrared spectroscopy. The rate of weight loss was accelerated when both BaTiO3 and platinum metal were present, and the presence of both metal and ceramic enhanced the production of CO2. The activation energy and pre-exponential factor were determined by analysis of the weight-loss data with a first-order kinetics model. Then, the decomposition kinetics were incorporated into a coupled heat- and mass-transport model to predict pressure increases as a function of the heating cycle. The heating cycles determined in this manner then were used to evaluate the yield of capacitors 1.3,3.8 cm long and 0.3,1.3 cm high. The optimum yield was realized at an aspect ratio (height:length) of 1:3. [source] Necessary Conditions for the Formation of {111} Twins in Barium TitanateJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 11 2000Byoung-Ki Lee The experimental conditions for {111} twin formation in BaTiO3 were investigated. When BaTiO3 compacts without excess TiO2 were sintered either in an oxidizing atmosphere (air) or in a reducing atmosphere (95N2,5H2), no {111} twins formed within the BaTiO3 grains and no abnormal grain growth occurred. In contrast, many {111} twins were present within the abnormally grown grains in the excess-TiO2 -containing BaTiO3 samples sintered in air, while no twins were observed in the excess-TiO2 -containing samples sintered in 95N2,5H2. X-ray diffraction analysis showed that excess TiO2 forms a Ba6Ti17O40 phase during sintering with the space group A2/a in air and a Ba6Ti17O40,x phase with the space group C in 95N2,5H2. It appears therefore that excess TiO2 and an oxidizing atmosphere are necessary for {111} twin formation in BaTiO3. These results may also indicate that the interface structure between BaTiO3 and Ba6Ti17O40 influences the twin formation. [source] Low-Temperature Synthesis of Phase-Pure 0D,1D BaTiO3 Nanostructures Using H2Ti3O7 TemplatesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 9 2010Duk Kyu Lee Abstract One-dimensional (1D) barium titanate (BaTiO3) nanowires, which were uniformly covered with 0D BaTiO3 nanocrystals, were synthesized by using a simple solvothermal reaction of protonated trititanate (H2Ti3O7) nanowires with barium hydroxide octahydrate [Ba(OH)2·8H2O] at 80 °C in ethanol/water mixed solvent systems. The compositions of the mixed solvents , the volume ratio of ethanol to deionized water , was a key controlling parameter in order to determine the phase formation and primary particle size of the 0D BaTiO3 nanocrystals. Single-phase cubic perovskite BaTiO3 started to form at 80 °C in a mixed solvent containing more than approximately 60,% by volume of ethanol. Field-emission scanning electron microscopy (FESEM) and high-resolution transmission electron microscopy (HRTEM) analysis revealed that the as-prepared BaTiO3 retained its wire-shaped morphology with nanocrystals on the surface. Furthermore, the synthetic mechanism of the 0D-1D BaTiO3 nanostructures was demonstrated in view of the dielectric tuning of the mixed solvent and the similarities between the crystal structures of BaTiO3 and H2Ti3O7. [source] Potential Bioelectroactive Bone Regeneration Polymer Nanocomposites with High Dielectric Permittivity,ADVANCED ENGINEERING MATERIALS, Issue 10 2009Zhi-Min Dang The frequency dependence of the dielectric permittivity of (barium titanate,hydroxyapatite)/poly(vinylidene fluoride) three-phase nanocomposites is investigated at room temperature and different fractions of barium titanate. The permittivity increases with increasing concentration of barium titanate. A weak decrease in permittivity is also observed for frequencies below 106 Hz. The SEM image inset in a dielectric permittivity vs. frequency curve shows that rod-like hydroxyapatite and sphere-like barium titanate nanoparticles exist in the three-phase nanocomposites. [source] Synthesis and Dielectric Properties of Niobia Coating on BaTiO3INTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 6 2009Jia-Jia Gan Different from conventional powder mixing, this study demonstrates a method of homogeneous coating for niobia (Nb2O5) on ferroelectric barium titanate (BaTiO3) powders. The precipitation of Nb coating with pH has been determined quantitatively by the inductance-coupled plasma method. Crystalline phases were determined by X-ray diffractometry, and the formation of a "core-shell" structure with a Nb concentration gradient was observed by a transmission electron microscope with X-ray energy-dispersive spectroscopy. The dielectric constant (K) of the samples prepared by the nanocoating method showed a more stable temperature coefficient of capacitance and well satisfied the requirements of X7R. [source] On the tetragonality of the room-temperature ferroelectric phase of barium titanate, BaTiO3JOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 3 2009Dean S. Keeble The room-temperature phase of the important ferroelectric material barium titanate, BaTiO3, was re-investigated by single-crystal X-ray diffraction on a sample grown by the top-seeded solution growth method, with the intention of demonstrating once again that the structure has tetragonal symmetry consistent with the space-group assignment P4mm and thus resolving recent controversy in the scientific community and literature [Yoshimura, Kojima, Tokunaga, Tozaki & Koganezawa (2006). Phys. Lett. A, 353, 250,254; Yoshimura, Morioka, Kojima, Tokunaga, Koganezawa & Tozaki (2007). Phys. Lett. A, 367, 394,401]. To this end, the X-ray diffraction pattern of a small (341,µm3) sample of top-seeded solution-grown BaTiO3 was measured using an Oxford Diffraction Gemini CCD diffractometer employing Mo,K, radiation and an extended 120,mm sample-to-detector distance. More than 104 individual diffraction maxima observed out to a maximum resolution of 0.4,Å were indexed on two tetragonal lattices. These were identical to within the standard deviations on the lattice parameters and were related to each other by a single rotation of 119.7° about the [11] direction of the first tetragonal lattice (the major twin component), although the actual twinning operation that explains the observed diffraction pattern both qualitatively and quantitatively is shown to be conventional 90° twinning by the m[101] operation. Importantly, it is not necessary to invoke either monoclinic symmetry or a coexistence of tetragonal and monoclinic phases to explain the observed diffraction data. [source] Dispersion of nanoscale BaTiO3 suspensions by a combination of chemical and mechanical grinding/mixing processesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 3 2007Kuo-Liang Ying Abstract The colloidal stability of aqueous nanometer- and micrometer-scale barium titanate (BaTiO3) utilizing poly (methacrylic acid) (PMAA-Na) and polyacrylamide/(,- N,N -dimethyl- N -acryloyloxyethyl)ammonium ethanate (PDAAE) was investigated. In addition to chemical dispersants, the effects of mechanical milling using either conventional ball milling or nanogrinding/-mixing on the dispersion of BaTiO3 suspensions were also studied. Characterization of the particle size distribution (d50), viscosity, and morphology of BaTiO3 particles in the suspensions revealed that a sole chemical dispersant or mechanical milling was insufficient to achieve nanometer-scale dispersion. The best dispersion results were obtained with a combination of PMAA-Na dispersant and nanogrinding/-mixing, which could provide sufficient electronic repulsive force and shear force to disperse the 80-nm BaTiO3 powders uniformly in the aqueous suspension. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007 [source] Carbon combustion synthesis of complex oxides: Process demonstration and featuresAICHE JOURNAL, Issue 10 2005K. S. Martirosyan Abstract Carbon combustion synthesis of oxides (CCSO) is a novel process to rapidly produce high-purity, submicron, and porous powders of complex oxides. It is a modified form of self-propagating high temperature synthesis (SHS) that uses carbon as the fuel instead of a pure metal. The CO2 release increases the porosity and friability of the products. Like SHS, it is much faster (order of minutes) than the calcination processes (order of hours). CCSO has several advantages over SHS (the initial components are less expensive, porosity of the products is up to 70%). CCSO can produce complex oxides, such as LaGaO3, which cannot be produced by SHS. The feasibility and features of CCSO are illustrated by its use in producing barium titanate, lithium manganese, and lanthanum gallium oxides. The carbon concentration enabled control of the moving front temperature and average velocity and the particle size and surface area. © 2005 American Institute of Chemical Engineers AIChE J, 2005 [source] Synthesis of Micron-Scale Platelet BaTiO3JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 4 2007Dan Liu Micron-scale platelet barium titanate was synthesized using a twostep molten salt and topochemical technique. Plate-like BaBi4Ti4O15 was first synthesized as a precursor by molten salt synthesis. Then, Bi3+ in the precursor was replaced by Ba2+ and formed perovskite-structure BaTiO3 through a topochemical reaction. The BaTiO3 single crystals have an average size of 5,10 ,m and a thickness of 0.5 ,m. The purpose of this article is to control the particle shape with desired structure. High aspect ratio BaTiO3 platelets are suitable templates to obtain textured ceramics (especially Pb(Mg1/3Nb2/3)O3,32.5PbTiO3) by the templated grain growth process. [source] Effect of Green Density on the Thermomechanical Properties of a Ceramic During SinteringJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 8 2006Sam E. Schoenberg The thermomechanical properties of a commercial barium titanate were experimentally or theoretically determined for samples with green densities ranging from 45% to 55%. For stresses less than 300 kPa, sample deformation was determined to be linear viscous for all three stages of sintering. The shrinkage rates at a given temperature can differ by up to ,25% as the green density changes from 45% to 55%, and the maximum shrinkage rate increased with decreasing green density. The increase in shrinkage rate with lower green density samples persisted through the final sintering stage. The viscosity was determined by cyclic loading dilatometry to range from 5 to 6 GPa·s in the initial stage of sintering, to 2 GPa·s in the intermediate stage, and to increase to 10,20 GPa·s for all specimens in the final stage of sintering. Differences in the final-stage viscosity were attributed to grain size differences. Relaxation times for the sintering body were estimated to be less than 1 s, indicating that viscous behavior is dominant throughout the sintering process. [source] Preparation of a Monodispersed Suspension of Barium Titanate Nanoparticles and Electrophoretic Deposition of Thin FilmsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 8 2004Juan Li A transparent and stable monodispersed suspension of nanocrystalline barium titanate was prepared by dispersing a piece of BaTiO3 gel into a mixed solvent of 2-methoxyethanol and acethylacetone. The results of high-resolution transmission electron microscopy (HR-TEM) and size analyzer confirmed that the BaTiO3 nanoparticles in the suspension had an average size of ,10 nm with a narrow size distribution. Crystal structure characterization via TEM and X-ray diffraction indicated BaTiO3 nanocrystallites to be a perovskite cubic phase. BaTiO3 thin films of controlled thickness from 100 nm to several micrometers were electrophoretic deposited compactly on Pt/Ti/SiO2/Si substrates. The deposited thin film had uniform nanostructure with a very smooth surface. [source] Synthesis and Electrorheological Characterization of Polyaniline/Barium Titanate Hybrid SuspensionMACROMOLECULAR SYMPOSIA, Issue 1 2006Fei Fei Fang Abstract As organic/inorganic composites having attracted much attention due to their heterogeneous physical properties, conducting polyaniline (PANI) and barium titanate (BaTiO3) which possesses large electronic resistance and excellent dielectric strength, were utilized to synthesize PANI/BaTiO3 hybrid which is applicable for an electrorheological (ER) material via ,in-situ' oxidative polymerization. Physical properties of the obtained PANI/BaTiO3 composites were characterized via Fourier-transform infrared spectra (FT-IR), thermogravimetry analysis (TGA), and scanning electron microscopy (SEM). The ER behaviors were investigated via a rotational rheometer, and their shear stresses were fitted using our previously proposed rheological equation of state. [source] Fully embedded lumped LC-quadrature hybrid coupler into organic packaging substrate for power samplingMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 3 2009Yi Jae Lee Abstract In this article, fully embedded lumped LC-quadrature hybrid coupler are designed, fabricated, and characterized into multilayered organic packaging substrate. This embedded device comprised high Q MIM capacitors and circular spiral stacked inductors. For realizing fully embedded high Q capacitor, barium titanate (BaTiO3) composite high dielectric film was utilized. The measured return loss and isolation were better than 25 dB. Measured insertion loss was about 0.38,0.42 dB at the frequencies ranged from 824 to 894 MHz. The coupler exhibited a coupling loss of 23.3,24 dB. The phase error between through and coupling ports was 1.2°,2.4°. It has a size of 2.8 mm ×2.95 mm ×0.77 mm (height), which is the smallest one in the couplers developed onto the packaging substrate. The measured performance characteristics were also well matched with the 3D EM simulated ones. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 845,848, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24173 [source] Dielectric properties of polyethylene terephthalate/polyphenylene sulfide/barium titanate nanocomposite for application in electronic industryPOLYMER ENGINEERING & SCIENCE, Issue 8 2010Monika Konieczna Polymer/ceramic nanocomposites designed for application as electronic packaging were prepared using corotating twin-screw extruder. The dielectric properties of the composites made from polyethylene terephthalate (PET), polyphenylene sulfide, and barium titanate were studied as a function of BaTiO3 fraction in the range between 0.75 and 1.5 wt%. Processing parameters were optimized in order to obtain the nanocomposites with appropriate dielectric properties like dielectric permittivity ,,, dielectric losses ,,, and their temperature stability in a wide frequency range. The measurements showed the increase of the dielectric permittivity value ,, in the composites in comparison to both pure polymers. The dielectric loss factor tg, of the composites was found to be much smaller than that of the pure PET. The weak influence of the ceramics on the temperature stability of the dielectric properties of the composites was stated. POLYM. ENG. SCI., 50:1613,1619, 2010. © 2010 Society of Plastics Engineers [source] Polymeric composites for use in electronic and microwave devicesPOLYMER ENGINEERING & SCIENCE, Issue 3 2004Alexandre Moulart The dielectric and conductive properties of thermoplastic (ABS) composites filled with ceramic powder (barium titanate), conductive powders (carbon black, copper) and conductive fibers (carbon, steel) were investigated for use in electromagnetic crystals and microwave devices. Barium titanate/ABS composites were produced that had dielectric constants over 8 and loss tangents of 0.01, which are the requirements for electromagnetic crystals. Carbon black/ABS and steel fiber/ABS composites were obtained with conductivities suitable for electromagnetic shielding (over 10,3 S/cm). Fused decomposition modeling was tested as a method for building electromagnetic crystals and showed promising results. Polym. Eng. Sci. 44:588,597, 2004. © 2004 Society of Plastics Engineers. 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