BaTiO3 Nanopowders Research Articles

Electric and Damping Properties of PU Based IPNs-BaTiO3 Nanocomposites

(PU/UP IPNs)-BaTiO3 nanocomposites with different amounts of BaTiO3 nanopowder are prepared and polarized. The ferroelectric and dielectric properties are detected and the relationship between electric properties and damping properties are discussed in detail. Results indicate that the synergistic effects can be created successfully by elastic damping of polymer, frictional damping of BaTiO3, and piezoelectric damping of nanocomposites after poling. The nanocomposites increase the damping property evidently and sustain mostly ferroelectric and dielectric characters of inorganic phase. The introduction of BaTiO3 into IPNs decreases the resistivity, and this has advantages to enlarge the damping loss factor (tanδ).

A Study on the Preparation of Nano-Crystalline Barium Titanate Powder by a Sol-Gel Method

In this work, high purity BaTiO3 (BT) nano-powders by a sol-gel process was prepared with Ba(NO3)2 and Ti(C4H9O)4 materials in order to acquire uniform size grains. The effects of the crystallinity, microstructure of BT nano-powders calcined at different temperatures and dielectric properties of the ceramics were investigated by XRD, SEM and impedance analyzer, respectively. Scanning electron microscopy and X-ray diffraction investigation revealed cubic plates and crystallite size. The results revealed that crystallite size and calcination temperature of BT and influence on the dielectric constant.

Dielectric Thin Film from Barium Titanate Nanopowders

BaTiO3 nanopowders prepared by using organic acid precursor method were thermally grown onto steel under a vacuum of 10−5 torr, using an Edwards E-306 coating unit. Reflection measurements of coated steel, in the spectral range 200-1100 nm, were carried out using a double beam spectrophotometer. Characterizations of the deposited layer such as adhesion, hardness, dielectric properties and corrosion resistance have been investigated. Surface morphology of fabricated thin film using scanning electron microscope (SEM) reveal that adhered, dense and void free deposited film enables the coated steel to exhibit high corrosion resistance. The microhardness is improved from 116 HV for uncoated steel to 464 HV for coated ones. Dielectric properties were investigated for coated and pure steel samples. The impedance and phase were found to increase with frequency for the as-deposited samples.

Coating of BaCO3Crystals with TiO2: Versatile Approach to the Synthesis of BaTiO3Tetragonal Nanoparticles

The fabrication of the very thin (<1 μm) dielectric layers for the next generation of miniaturized multilayer ceramic capacitors will require barium titanate, BaTiO3, particles of 100−200 nm with narrow particle size distributions, high density, and high tetragonality. Composite particles, consisting of a BaCO3 core and a TiO2 shell, can be efficiently used for the solid-state synthesis of nanocrystalline tetragonal BaTiO3 powders at moderate temperatures. A uniform layer of amorphous titania has been formed on the surface of fine barium carbonate crystals suspended in a peroxotitanium(IV) solution by a precipitation process. Formation of single phase BaTiO3 from the BaCO3@TiO2 particles occurs by a single step reaction at 600−650 °C, whereas the conversion of mechanical mixtures of nanocrystalline raw materials BaCO3 and TiO2 requires temperatures ≥800 °C and produces much coarser powders. The lowering of the reaction temperature can be attributed to the maximization of the contact surface between the reactants and to the minimization of diffusion distances. The BaCO3@TiO2 particles undergo spontaneous fragmentation and spheroidization during the reaction, and, consequently, the resulting BaTiO3 nanoparticles have no memory of the initial shape of the barium carbonate crystals. The final powders have high density (94−98%), high tetragonality (c/a ratio: 1.006), average particle size of 140 nm, and no agglomerates bigger than 300 nm. The solid-state reaction of BaCO3@TiO2 particles is a simple process that could be competitive with the oxalate and the hydrothermal routes for the mass production of high-quality BaTiO3 nanopowders.

Zirconia coating of hydrothermal BaTiO3 nanopowder and its dielectric properties

Zirconia coating of hydrothermal BaTiO3 nanopowder and its dielectric properties

Preparation of BaTiO3 Nanopowders and Sintering to Dense Nanocrystalline Ceramics

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Size effect on crystal structure and chemical bonding nature in BaTiO3 nanopowder

The size effect on the crystal structure including the chemical bonding nature has been investigated for several kinds of BaTiO3 nanopowder with the particle sizes down to 50 nm in diameter, by means of powder diffraction using high-energy synchrotron radiation. The Rietveld refinement reveals that the BaTiO3 nanopowder consists of tetragonal and cubic structure components at 300 K. The feature of coexistence can be illustrated by the core/shell model for the particle, in which the shell with a cubic structure covers the core with a tetragonal structure. The thickness of the cubic shell is almost constant irrespective of the particle sizes, and is estimated as approximately 8 nm. Hence, the critical particle-size, where the entire particle is covered with the cubic shell, is suggested as 16 nm. The charge density distributions of the BaTiO3 nanopowder in the cubic phase at 410 K are revealed by the maximum entropy method. Changes in the bonding electron density and the ionic valence expected are not observed clearly even in the 50 nm crystal compared with the bulk crystal.

Influence of BaTiO3 on damping and dielectric properties of filled polyurethane/unsaturated polyester resin interpenetrating polymer networks

A series of BaTiO3 fiber and nanopowder unfilled and filled interpenetrating polymer networks (IPNs) composed of polyurethane (PU) and unsaturated polyester resin (UP) are prepared by simultaneous polymerization process. The effect of PU/UP component ratios, the types and amounts of BaTiO3 filled, the polarization treatment to filled IPNs, on the damping properties are investigated by dynamic mechanical thermal analyzer (DMTA). The morphology and microstructures of unfilled and filled IPNs are examined by transmission electron microscope (TEM). The dielectric loss and dielectric constant at different temperatures are studied by AC impedance analyzer. Moreover, the relationship between damping and dielectric properties is discussed in terms of dielectric constant and dielectric loss measured. The results show that the PU/UP component ratios in IPNs, the types of filler, and the amount of nanopowder added all affect the damping behaviors and degree of phase separation of unfilled and filled IPNs. Through polarization treatment, the filled IPNs exhibit synergistic action in systems caused by elastomeric damping mechanism, interfacial frictional damping mechanism and piezoelectric damping mechanisms. The maximum value of E″ of filled IPNs with 70% BaTiO3 increase above 100 MPa and the temperature ranges of tan δ > 0.3 is higher than 100°C compared with unfilled IPNs. Moreover, the maximum value of E″ and the temperature ranges of tan δ > 0.3 increases dramatically after polarizing process. The dielectric properties and its relation with damping properties studies reveal that the temperature ranges exhibit excellent consistency of maximum dielectric loss and dielectric constant with damping loss factor.

The Effect of Oxygen Vacancies in the Early Stages of BaTiO3 Nanopowder Sintering

The Effect of Oxygen Vacancies in the Early Stages of BaTiO₃ Nanopowder Sintering

Size Effects in BaTiO3 Nanopowders Studied by EPR and NMR

To study the effect of the particle size on the material properties, Mn 2 + EPR and 137 Ba NMR measurements were performed on BaTiO 3 particles with average diameters between 15 nm and 255 nm. Typical changes in the fine structure tensor and the quadrupole coupling tensor, respectively, are observed which allow us to make conclusions about the structure model for the nanograins in the ferroelectric tetragonal phase.

Size driven phase transition of barium titanate nanoparticles prepared by plasma chemical vapor deposition

Size driven phase transition of barium titanate nanoparticles prepared by plasma chemical vapor deposition

Glycothermal synthesis and characterization of tetragonal barium titanate

Tetragonal barium titanate (BaTiO3) particles were synthesized at temperature as low as 220°C through glycothermal reaction by using Ba(OH)2·8H2O and amorphous titanium hydrous gel as precursors and 1,4-butanediol and water as solvent. XRD, DSC and Raman data support that glycothermal processing method provides a simple low-temperature route for producing tetragonal BaTiO3 nanoparticles without alkaline mineralizers. It is also demonstrated that the size and shape of BaTiO3 particles can be controlled by reaction conditions such as reaction temperature and various volume ratio of 1,4-butanediol/water. This processing method can fabricate BaTiO3 powders with narrow size distribution and low aggregation. In addition, BaTiO3 nanopowder with a Ba/Ti atomic ratio of 1.000±0.003 can be obtained in a reproducible manner with glycothermal process.

Phase Transition and Physical Characteristics of Nanograined BaTiO3 Ceramics Synthesized from Surface‐Coated Nanopowders

Nanograined BaTiO3 ceramics prepared from 40‐nm‐size BaTiO3 nanopowders exhibited the cubic as well as the tetragonal phase, while nanograined BaTiO3 ceramics prepared from BaTiO3 nanopowders coated with Mn had only the tetragonal phase. The dielectric constant of the latter was 10 times larger than that of the former; the latter exhibited PTCR behavior with a resistivity jump ratio of about 5.0 × 104. These physical properties of the BaTiO3 ceramics appeared to be significantly affected by the strain near grain boundaries; such strain resulted in a phase transition from the cubic to the tetragonal phase in the nanograined BaTiO3 ceramics, even though the grain size was about 40 nm.

The preparation of porous perovskite membranes using BaTiO3 nanopowders

The aim of this study was to develop a simple and reliable procedure in order to prepare composite membranes through the deposition of thin porous layers of perovskite-like oxides onto ceramic porous supports. BaTiO3 nanopowders with controlled properties were obtained by Low Temperature Aqueous Synthesis (LTAS) and used as starting materials for the thin film deposition. Process parameters were determined in order to obtain a stable suspension of the nanopowder. The nanopowder was then effectively used to realize the layers with controlled properties. The results of characterisation tests indicated that the porosity of the deposited layers was of a mesoporous type and that the starting nanopowder did not undergo structural changes after the deposition process.

Preparation of Nanocrystalline BaTiO3 Characterized by in Situ X-ray Absorption Spectroscopy

Barium titanate (BaTiO3) nanopowders were prepared through a combined polymerization and pyrolysis of a metallo-organic precursor. The mean particle size dm could be adjusted by choosing appropriate reaction temperatures and tempering atmospheres. In the present in situ study of this particular solid-phase reaction, X-ray absorption near-edge structure (XANES) spectroscopy at the Ti K and Ba L3 edges was applied in the preparation route of BaTiO3 nanopowders. A pronounced distortion of the lattice symmetry was found to occur in very fine BaTiO3 nanopowders (dm 20 nm). In addition, Ti K XANES investigations were performed in the formation of titanium dioxide (TiO2) nanopowders as a reference case, enabling identification of amorphous TiO2 as an intermediate in the BaTiO3 preparation route.