Structure Of Barium Titanate Research Articles

Photocatalytic properties of BaTiO3/Fe2O3 under visible and ultraviolet irradiation

Nanosized composite materials based on BaTiO3 with 0.5 % and 1 % Fe2O3 were prepared by the sol-gel method and subsequent heat treatment. This work showed that increasing the content of iron(III) oxide in a heterostructured material affects the bleaching of the dye rhodamine B upon irradiation with visible and ultraviolet light. The highest photocatalytic activity was observed on the solid surface of the samples in an air environment under both visible and UV irradiation. The BaTiO3/0.5 % Fe2O3 sample was found to be most effective in an air environment when irradiated with an artificial visible light source. The increase in efficiency could be due to the best separation of charge carriers at the interface between the barium titanate and iron(III) oxide structures and the highest concentration of the resulting radical anions. An increase in the mass fraction of Fe2O3 led to a decrease in the efficiency of the nanoscale composite photocatalyst, which was due to a greater recombination of charge carriers.

Influence of Silicon Dioxide on the Structure and Dielectric Properties of Barium Titanate

Influence of Silicon Dioxide on the Structure and Dielectric Properties of Barium Titanate

Nanoimprinting Solution-Derived Barium Titanate for Electro-Optic Metasurfaces.

Electro-optic metasurfaces have demonstrated significant potential in enhancing the modulation speed and efficiency for fast and large-scale free-space optical devices. Barium titanate has a strong electro-optic Pockels coefficient, but its availability in thin-film form is restricted due to costly growth processes or low thickness. Here, we fabricated active metasurfaces using an etch-free bottom-up process with sol-gel-based polycrystalline barium titanate with a large electro-optic coefficient similar to bulk lithium niobate. We achieve strong hybrid Mie/surface lattice resonances with a quality-factor of 200 at 633 nm wavelength, enhancing the light-matter interaction and therefore the Pockels effect. The metasurface transmission is electro-optically modulated with up to 5 MHz driving frequency at low voltages of less than 1 V thanks to resonant enhancement of the modulation amplitude by 2 orders of magnitude. This successful demonstration of electro-optic modulation in nanoimprinted barium titanate structures paves the way for low-cost and large-scale free-space modulators or tunable metalenses.

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

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

Effects of yttrium doping on structural, electrical and optical properties of barium titanate ceramics

In this report, we study the Yttrium-doped Barium Titanate (Y-BT) Ba1 − xYxTiO3 (with x = 0.00, 0.01, 0.03, 0.05, 0.07 mmol) perovskite ceramics synthesized by sol-gel method. The as-made powder samples were pressed into a pellet shape and subsequently sintered at 1300 °C for 5 h in air. The structural, morphological, electrical, and optical properties of the synthesized samples were investigated by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), impedance analyzer, and UV-Vis-NIR Spectroscopy respectively. The XRD study revealed the formations of single phase tetragonal structure of Barium Titanate (BT) with ∼23–33 nm mean crystallite size. The crystallite size increases initially with Y-doping, found at about 33 nm for x = 0.01, and reduces for increase in Y3+ concentration further. The microstructural study from FESEM depicts the uniform distribution of compact and well-faceted grain growth for Y-BT in contrast with undoped barium titanate. The average grain size (∼0.29–0.78 μm) of the Y-BT decreases with increasing doping concentration. Frequency-dependent impedance analyses show enhanced dielectric properties like dielectric constant, quality factor, and conductivity with low dielectric loss in the presence of Yttrium. The optical bandgap energy (∼2.63–3.72 eV) estimated from UV-Vis-NIR diffuse reflection data shows an increasing trend with a higher concentration of yttrium doping.

Determination of the doping profile of lanthanum impurities in thin-film barium titanate structures

The paper presents a calculation of doping concentration profile in a two-layer barium titanate film, one of the layers of which contains lanthanum impurity. The theoretically predicted distributions were experimentally verified. Influence of the doping profile on the magnitude of the electrocaloric (EC) response of ferroelectric films is assessed by numerical simulation. It is demonstrated that at the same La concentration, the magnitude of the EC effect can change by 40% due to the distribution of the lanthanum concentration in the structure. The results obtained allow optimizing the technological process to ensure the required characteristics of ferroelectric thin films.

Multifunctional tunable visible light metalens based on double-layer barium titanate.

A tunable metalens plays an indispensable role in the development of integrated optics, multi-imaging systems, etc. We propose a multifunctional tunable metalens that combines a double-layer barium titanate (BTO) structure and geometric phase in the visible light band. The refractive indices of the upper and lower layer BTO nanorods can be tuned continuously and independently by applying external voltage (0-60 V), and the lower layer can be converted between a full-wave plate and normal scattering unit, while the scatterers of the upper layer can be switched between a half-wave plate and full-wave plate. The voltages of the upper and lower layers can be adjusted to achieve different functions such as optical switches, conversion between monofocal and bifocal metalenses, adjustment of bifocal intensity, and broadband focusing (585-690 nm). Simulation results show that the multifunctional tunable metalens has a good focusing effect. A metalens with high focusing efficiency, dynamic reconfigurability, and a switching function has tremendous application potential in the fields of multifunctional devices, biomedicine, optical communication, imaging, and so on.

Kittel’s Brief Comments Endorsing an Alternative View on Barium Titanate

Charles Kittel has written a masterpiece book, “Introduction to Solid State Physics” (ISSP). He mentions in the chapter on ferroelectrics in detail that barium titanate is the typical displacive-type ferroelectric compound where the Ti4+ displacement develops a dipole moment, which has made a deep impression in our mind. The author’s group, however, has arrived at an alternative viewpoint on the unit cell structure of barium titanate based on their exhaustive experimental studies. Accordingly, the author sent his relevant papers in 2006 and 2007 to Kittel. He endorsed the results frankly with reminiscence. He mentioned revising the ferroelectric chapter of ISSP according the author’s suggestions. It appears to be admissible to publish details now after Kittel has passed away. A long time misunderstanding of the phase transition in barium titanate is due to the text book knowledge of ISSP.

Study on microstructural influence of graphene on synthesis of BaTiO3

Abstract A composite of polycrystalline Ferroelectric ceramics Barium titanate (BaTiO3) in perovskite (ABO3) structure with Graphene was prepared from BaCO3 and TiO2 mixture by sonicating, ball milled and followed by sintering at 1000 °C. Graphene of 0.04 mol added to BaTiO3 and sintered at 1000 °C to develop the crystalline and microstructural properties of composite. Composite sintered at 1000 °C temperature mostly shows pure barium titanate (BaTiO3) poly crystalline single phase material with presence of few secondary unwanted phases. X-ray diffraction (XRD) of the composite exhibits substantial effect of graphene on the crystal structure of barium titanate (BaTiO3). Micro Raman confirms the growth of BaTiO3.FESEM of Barium titanate (BaTiO3) with graphene (0.04 mol) almost shows change in crystal growth where grown of phases are clearly distinguished with porous free nature.

Study of changes in the crystal structure of BaTiO<sub>3</sub> under the effect of X-ray radiation

X-ray diffractometers are widely used in studying the atomic structure of mono- and polycrystalline substances. The radiation source of conventional laboratory diffractometers is a soldered x-ray tube with the maximum power consumption 1 – 3 kW. The radiation spectrum of the tube is determined by the anode material (usually, these are spectrally pure metals Cr, Ni, Fe, Cu, Mo, Ag). The wavelengths of the characteristic radiation range within 0.56 – 2.29 Е . We present the results of studying the effect of X-ray radiation power on the structure of barium titanate. Comparison of the diffraction spectra of BaTiO 3 (laminar polydomain ferroelectric single crystal and nanopowder samples) showed that the spectrum structure changes significantly with an increase in the power of X-ray beam (Cu K α radiation) from 100 (5 mA, 20 kV) to 800 W (20 mA, 40 kV). For example, a rearrangement of the domain structure and, hence, a change in the dielectric characteristics of the material were observed for BaTiO 3 single crystal. The rearrangement was accompanied by the formation of continuous transition zones (between domains) containing a cubic phase. As for the BaTiO 3 nanopowder, a change in the structure was observed in the direction of the axis of spontaneous polarization c and an invariance of the structure in the plane a – c . The results obtained can be used to control the physical properties of ferroelectric and ferroelastic materials, in particular, the memristor characteristics of epitaxial films based on YBa 2 Cu 3 O 7– δ due to changes in their twin structure under X-ray irradiation.

Effect of Nickel and Cobalt co-substitution on the structural and dielectric properties of Barium Titanate ceramics

The influence of Nickel and Cobalt co-substitution on the structure and dielectric properties of barium titanate (BaTiO3) ceramics has been investigated. Nickel and Cobalt co-substituted BaTiO3 ceramics with general formula BaTi1−x(Ni,Co)xO3 has been synthesized for x = 0.0, 0.02, 0.04 and 0.08 through conventional solid state reaction route. The structural analysis carried out by X-ray diffraction reveals the successful incorporation of Ni2+ and Co2+ ions in the Ti4+ site of BaTiO3 with all samples under study having tetragonal structure. However the tetragonality (c/a ratio) seems to be decreasing with increase of co-substitution. The dielectric measurements are done at different frequencies and temperatures. The room temperature dielectric constant decreased considerably for the Ni and Co co-substituted samples. The phase transition of the BaTi1−x(Ni,Co)xO3 has been investigated by studying the temperature dependence of dielectric constant. Nickel and Cobalt co-substituted samples showed diffused nature of phase transition with a notable reduction in the Curie temperature with the increase of co-substitution. The Curie temperature is reduced to 104 °C for x = 0.08 composition whereas for x = 0.0 the Curie temperature is 123 °C. Enhancement in conductivity is observed with addition of Nickel and Cobalt addition. Nearest-neighbour hopping model is used to explain the conduction in the samples under study and energy of activation for conduction is calculated from Arrhenius plot.

Effect of mechanical stresses on the domain structure of barium titanate single crystals

This review article summarizes the material of years of research on the impact of mechanical stresses on the domain structure of multiaxhetoelectrics using the example of barium titanium monocrystals. Since the discovery of the ferroelectric properties of barium titanate in 1944, this material has been the subject of comprehensive investigation as the first practically important and perhaps the most famous ferroelectric. The domain structure of barium titanate is sensitive to mechanical stresses arising both from simple uniaxial compression and from point impacts by local mechanical loading. Mechanical stress applied to a ferroelectric crystal may have a significant effect on dielectric and piezoelectric properties. In particular, 90-degree domain switching is possible under the influence of stresses. The most interesting experimental results are obtained in the study of elastoplastic processes in BaTiO 3 originating from local mechanical stresses. The following features are found and studied: development of strained region around the point of application of the load; “internal” 90-degree domain that does not extend to the crystal surfaces and does not close upon other domains; the growth of 90-degree domains under the influence of residual mechanical stresses; growth of cracks along charged 90-degree domain walls. The notions of “ferroplastic effect” (crystal deformation due to the formation of 90-degree ferroelectric domains) and “ferromechanical effect” (crack formation and growth along charged 90-degree domain walls) are introduced. The hypothesis of a significant role of oxygen vacancies in the processes of 90-degree domain reorientation was put forward and experimentally confirmed. In particular, an increase in the concentration of oxygen vacancies by reducing annealing of barium titanate single crystals creates more favorable conditions for the appearance of an "internal" 90-degree domain under local mechanical load. The study of the mechanisms governing the formation of a domain structure in ferroelectric crystals remains an important problem of modern materials science.

Study of the effect of La3+ doping on the properties of ceramics based on BaTiOx

The paper presents results of the influence of doping with lanthanum (La3+) on structural, conductive properties and phase composition of ceramics based on barium titanate, obtained by solid-phase synthesis, followed by thermal annealing at 800 °C for 5 h. The study found that the doping of the structure of barium titanate with lanthanum leads to a change in the phase composition with the phase (Ba0.94La0.06) (TiO3) of the substitution solid solution and impurity inclusions of the anatase and BaTi2O5 phases dominating. In this case, the formation of the cubic phase (Ba0.94La0.06)(TiO3) leads to a slight change in the average particle size and a decrease in the dielectric constant, as well as a shift of the absorption edge. According to IVC measurement data, it was found that for doped La3+ structures, a significant decrease in the magnitude of amperage, and a change in shape of IVC loop are observed. The increase in resistance for doped structures is due to the formation of lanthanum containing particles in the structure, as well as the change in the geometric dimensions of particles, leading to changes in the dislocation density, which creates additional distortions and defects in the structure.

Preparation and Study the Structure of Pure and Impure Barium Titanate with Zr4+ Ion

Preparation and Study the Structure of Pure and Impure Barium Titanate with Zr4+ Ion

Preparation and study the structure of pure and impure barium titanate with Mg2+ ion

Pure and doped barium titanate with Mg2+ ion at two molar ratios x= (5%, 10%) mol. has been synthesized by solid state reaction technique. The powders sintered at two temperatures (1000 °C and 1400 °C). An XRD technique was used in order to study the crystal structure of pure and doped barium titanate, which confirmed the formation of the tetragonal phase of BaTiO3, and then calculate the lattice parameters of pure and doped barium titanate, the addition of magnesium ion Mg2+ can lead to decreases lattice parameters.

Effect of Reagents on the Properties of Barium Titanate Synthesized in Subcritical Water

The structure and morphology of fine-crystalline barium titanate synthesized in a subcritical water fluid at 230°C and 2.9 MPa were studied. Barium oxide, barium hydroxide octahydrate (Ba(OH)2 · 8H2O), and two modifications of titanium oxide (rutile and anatase) were used as starting reactants. Relationships between the composition and properties of the reactants and the characteristics of the product (barium titanate) were revealed. They indicate that the product structure in the subcritical water is formed via a solidphase mechanism.

First-principle study of the polarization, atomic displacements and electronic structure of angular-deformed barium titanate

The influence of β and γ angular deformation on polarization, TiO(3) bond distances, atomic displacements, number of states, valence charge distributions and valance charge asymmetry of barium titanate (BaTiO3) has been investigated using local density approximation. The results show that for all angles of 89.5°≤ β&γ ≤ 90.5°, there is a clear correlation between polarization, TiO(3) bond distances, atomic displacements and number of states of the 3dz2 orbital. For the case of γ-deformation the values of polarization and the other parameters are approximately constant in the range of 89.8°≤γ ≤ 90.2° and an abnormal behavior is observed at γ = 89.6°. In this case valence charge asymmetry of Ti 3d orbital has a direct relation with the polarization and atomic displacements of Ti atoms for the whole region of γ, especially at γ = 89.6°. In the case of β-deformation, an approximately symmetrical behavior versus β variations is observed for all above-mentioned parameters. In this case, a direct relation between valence charge asymmetry of Ti 3d orbital, polarization and atomic displacements is remarkable only for β > 89.8° and the region of β < 89.8° does not reveal such a direct relation.

Preparation and study the structure of pure and impure barium titanate with Mg2+ ion

Pure and doped barium titanate with Mg2+ ion at two molar ratios x= (5%, 10%) mol. has been synthesized by solid state reaction technique. The powders sintered at two temperatures (1000 °C and 1400 °C). An XRD technique was used in order to study the crystal structure of pure and doped barium titanate, which confirmed the formation of the tetragonal phase of BaTiO3, and then calculate the lattice parameters of pure and doped barium titanate, the addition of magnesium ion Mg2+ can lead to decreases lattice parameters.

Characterization of BaTiO3 nanocubes assembled into highly ordered monolayers using micro- and nano-Raman spectroscopy

We investigated the influence of heat treatment on the crystallographic structure and ferroelectric phase transition behavior of barium titanate (BaTiO3, BT) nanocubes assembled into highly ordered monolayers, using tip-enhanced Raman spectroscopy (TERS), temperature-dependent micro-Raman spectroscopy, and scanning transmission electron microscopy (STEM). TER spectra from individual BT nanocubes with the size of about 20 nm were obtained with a side-illumination optical setup, and revealed that heat treatment enhances their tetragonality. The result of temperature-dependent micro-Raman spectroscopy showed that the ferroelectric phase transition behavior of the monolayers becomes similar to that of bulk BT through heat treatment in spite of their thickness. STEM observation for the cross-section of the heated BT nanocube monolayer showed that amorphous layers exist at the interface between BT nanocubes in face-to-face contact. These results indicate that the tetragonal crystal structure of BT nanocubes is stabilized by heat treatment and the formation of the interfacial amorphous layer during heat treatment may be a key to this phenomenon.

All Roads Lead to TiO2: TiO2-Rich Surfaces of Barium and Strontium Titanate Prepared by Hydrothermal Synthesis

Through high-resolution electron microscopy, the surface structure of barium titanate and strontium titanate nanoparticles are found to be terminated by a TiO2 double layer. These results confirm prior observations of TiO2-rich surface reconstructions on strontium titanate nanoparticles made hydrothermally at high pH and single crystals prepared with wet chemical etching. Of all the reconstructions observed on single crystals for these two materials, we report for first time the √13 × √13R33.7° structure on the {001} facets of hydrothermally prepared barium titanate and strontium titanate nanocrystals. The aqueous environment common to the two preparation methods preferentially leaves strontium and barium depleted from the A-sites near the surface and leads to TiO2-terminated surfaces for both materials. Analysis indicates that the observed structures are the thermodynamic lowest energy structures in aqueous conditions.