Structure Of BaTiO3 Research Articles

Luminescence of Pr-Doped Barium Titanate-Calcium Titanate Material

Pr-doped barium titanate-calcium titanate with rich barium is prepared by a sol-gel technique. A relatively strong red luminescence is observed in the material when Pr-BaTiO3 material does not exhibit obvious red luminescence. The wavelength range of luminescence near red light is broad. The phenomenon is discussed with respect to the substitute of Ca and the two-photon luminescence effect. The experimental results provide a possible way to develop new materials with photoluminescence properties that can be controlled by external fields because the microscopic structure of BaTiO3 can be changed by temperature, stress, electric field, and so on.

Ab initio simulation of the influence of zirconium impurity ions on the atomic and electronic structure of BaTiO3

The influence of zirconium impurity ions on the atomic and electronic structure of cubic barium titanate is studied theoretically by the electronic density functional theory and pseudopotential theory. It is shown that Zr ions induce local distortions in the BaTiO3 lattice, although neither zirconium nor titanium ions shift from their ideal positions, so that the structure of BaTi1 − xZrxO3 compounds remains cubic. The introduction of zirconium in an amount of 37.5 at % broadens the energy gap by 0.18 eV.

Three-scale analysis of BaTiO3 piezoelectric thin films fabrication process and its experimental validation

A three-scale analysis of crystal growth process is newly proposed based on the first-principles calculation and on the finite element analysis in order to generate a new biocompatible piezoelectric thin film. Crystal growth process of lead-free BaTiO3 thin films was designed and experimentally generated on SrTiO3(100), (110), (111), and MgO(100) substrates using the radio-frequency magnetron sputtering method. Crystal structures of BaTiO3 were measured by X-ray diffraction (XRD) θ/2θ scan. We used Pt for the electrode and measured piezoelectric strain constants d 33 using the ferroelectric measurement system. As a result, analytical crystal orientation fractions on SrTiO3(110) and (111) substrates had good quantitative agreement with experimental ones, and ones on SrTiO3(100) and MgO(100) substrates corresponded with these experimental crystal structures. Furthermore, analytically determined piezoelectric strain constants d 33 qualitatively showed a good agreement with experimental ones. Especially, for SrTiO3(100) and MgO(100) substrates, the differences of d 33 depending on orientation fractions were analyzed by the three-scale simulation accurately. Consequently, it is confirmed that the three-scale analysis is a useful simulation tool to design new biocompatible piezoelectric thin films.

First-Principles Calculations of Electronic Structure and Solution Energies of Mn-Doped BaTiO3

Doping with 3d transition metals, particularly Mn, is thought to play an important role in determining the reliability of dielectrics used in multi-layer ceramic capacitors (MLCCs). However, a detailed examination of the electronic structure, solution energies and compensation mechanisms of these systems is lacking. In this paper, the quantitative analysis of the substitution of Mn in perovskite-type BaTiO3 using first-principles calculations in combination with chemical thermodynamics is reported. The solution energies of dopants with vacancy and n-type and p-type charge compensations have been systematically calculated. Substitution onto the two crystallographically different cation sites in cubic BaTiO3 under four different thermodynamic conditions with different chemical potentials is also examined. Mn is found to be stable on Ti sites under all conditions examined, although its charge state varies. In the oxidizing limit, Mn substitutes for Ti as a Mn4+ ion, but in the reducing limit, Mn substitutes for Ti as a Mn2+ ion compensated by the formation of an O vacancy. Depending on the Fermi level of the system, the valence state of Mn varies from Mn4+ under p-type conditions, to Mn2+ under n-type conditions. Mn3+ is not found to be stable. These results agree well with the experimentally determined site preferences and valence states of Mn, and help to further elucidate the features of Mn-doped BaTiO3 at the atomic level.

Novel Multiferroic Lead-Free BaTiO<sub>3</sub>/FeBSi Composite Films

“Green” multiferroic BaTiO3/FeBSi composite films were grown by pulsed laser deposition and ion beam sputtering on general Pt/Ti/SiO2/Si substrates. Room temperature X-ray diffraction and Raman scattering show that the crystal structures of BaTiO3 and FeBSi are tetragonal and amorphous, respectively, and no additional or intermediate phase peaks appears in the composite films. A cross-sectional scanning electron microscopy image clearly demonstrates a 2-2 type structure with sharp interface between the top FeBSi layer and bottom BaTiO3 layer. The magnetic properties of the top FeBSi are obviously modified by the bottom BaTiO3. The composite films show obvious ferroelectric feature.

XRD studies on phase formation and the crystallite structure of BaTiO3 synthesized by HBM: the effect of calcination temperature

XRD studies on phase formation and the crystallite structure of BaTiO3 synthesized by HBM: the effect of calcination temperature

Probing Local Dipoles and Ligand Structure in BaTiO3 Nanoparticles

Improved routes for the preparation of nanoparticles, in conjunction with the development of more sophisticated structural probes for nanostructured materials, allows questions to be addressed regarding fundamental size limits on material properties. The property addressed here is structural off-centering, the molecular basis for the existence of switchable dipoles in polar materials, and whether it is turned off when particles become very small. This is probed using neutron scattering in a sample of free-standing, capped nanoparticles of the canonical perovskite ferroelectric, BaTiO3, with sizes near 5 nm. The structure, analyzed in reciprocal and real space, reveals the atomic correlations of the nanoparticle oxide and the capping benzyloxy ligand groups, and allows careful comparison with the structure of bulk BaTiO3. Even at these very small sizes, Ti is locally strongly off-centered, despite presenting cubic Bragg scattering.

Electron-Loss Near-Edge Structure (ELNES) of BaTiO3

Extended abstract of a paper presented at Microscopy and Microanalysis 2010 in Portland, Oregon, USA, August 1 – August 5, 2010.

Ferroelectric, piezoelectric and electrostrictive properties of Ba(Ti1−xSnx)O3 ceramics obtained from nanocrystalline powder

Abstract Ba(Ti1−xSnx)O3 powders with particle size 77.48 nm has been obtained through high energy ball milling. A detailed TEM study confirms the particle size to be 77.48 nm. Electromechanical coupling constant (Kp), piezoelectric strain constant (d33) and density follow decreasing trend with increasing tin concentration. As Sn concentration increases, ferroelectricity decreases with lower values of coercive field and remnant polarization, and this is due to replacement of Ti4+ ion by Sn4+ ion in the ABO3 structure of BaTiO3. Considerable strain values have been observed with very low value of degree of hysteresis and this implies good applicability of the ceramics.

Multiferroic properties in Ba0.93Bi0.07Ti1−xMnxO3 ceramics

Nominal composition of Ba0.93Bi0.07Ti1−xMnxO3 (x=0, 0.02, and 0.04) ceramics have been prepared by a modified Pechini method. X-ray diffraction analysis reveals that the samples are pure perovskite BaTiO3 (BTO) structure with no trace of impurity phase. The cell volume of the composites increases monotonously with the increase in Mn content, which indicates that Mn ions have been incorporated into the lattice of Ba0.93Bi0.07TiO3. The samples are experimentally confirmed to show ferromagnetic (FM) and ferroelectric behaviors simultaneously at room temperature. The temperature dependent magnetic behaviors show complex magnetic interactions including FM, antiferromagnetic, and paramagnetic. These results suggest that the dopant Bi and Mn help BTO transit from pure ferroelectric to multiferroic materials and the magnetic behaviors can be explained by the bound magnetic polaron model with inhomogeneity of Mn dopant distribution.

Structure and dielectric properties of BaTiO3–BiScO3 ceramics sintered by CaF2–4LiF aids

The effect of CaF2–4LiF (1–5 mol.-%) on the phase structure, microstructure and dielectric properties of 0·9BaTiO3–0·1BiScO3 (0·9BT–0·1BS) ceramics has been investigated. The 0·9BT– 0·1BS with CaF2–4LiF dopant ceramics sintered at 1100°C show a pure perovskite structure. Results show that CaF2–4LiF dopant can improve the sintering ability of 0·9BT–0·1BS ceramics when CaF2–4LiF content is below 3 mol.-%. The ceramics with 3 mol.-%(CaF2–4LiF) sintered at 1100°C exhibit a high permittivity, low dielectric loss as well as flat ϵ′ v. temperature curve indicating a favourable temperature stability, which are listed as follows: ϵ′25°C=1483, tan δ25°C=0·00309, Δϵ′/ϵ′25°C ≤ ± 13% at 100 kHz, in the temperature range from –55 to 150°C. This low sintering temperature allows using relatively inexpensive internal electrodes in the production of future capacitors.

Low‐Temperature Synthesis of Phase‐Pure 0D–1D BaTiO3 Nanostructures Using H2Ti3O7 Templates

AbstractOne‐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.

Sensitivity analysis and optimization of interatomic potential parameters for perovskites

An effective interatomic potential is crucial for molecular dynamics simulations. In this paper, a more effective optimization method for potential parameters is proposed. Sensitivity analysis is used to find the key parameters affecting the structure and properties most in all the potential parameters. The secondary parameters are ignored, and the dimension of the optimization is reduced. The genetic algorithm is adopted to optimize the key parameters. The results show that the structure and physical properties of BaTiO3 and SrTiO3 simulated by the optimized potential are more close to experimental data.

Mn-Doped BaTiO3 Thin Film Sintered Using Nanocrystals and Its Dielectric Properties

BaTiO3 thin films homogeneously doped with Mn were prepared by a novel powder-sintering thin-film process. Mn-doped BaTiO3 nanocrystals 5–7 nm in diameter were synthesized by a sol–gel method and sintered to form a highly densified microstructure containing columnar grains epitaxially grown on a (111)-oriented Pt/TiO2/Al2O3 substrate at a low temperature of 800 °C. On the basis of the results of various structural analyses, Mn was suggested to act as an acceptor in the perovskite structure of BaTiO3, which was also supported by the experimental finding indicating that the leakage current density was significantly improved compared with that of a nondoped BaTiO3 thin film. Moreover, the dielectric constant of the Mn-doped BaTiO3 thin film, 728 at 10 kHz with a loss tangent of 1.3%, was higher than that of the nondoped BaTiO3 thin film, probably owing to the electrostrictive effect induced by in-plane tensile stress. These results clearly indicate the feasibility of using doped BaTiO3 nanocrystals in the powder-sintering thin-film process for improving dielectric properties.

DIFFERENTIAL SCANNING CALORIMETRY INVESTIGATION OF PHASE TRANSITION IN BaZrXTi1-XO3

ABSTRACT Lead-free BaZrxTi1-xO3 (x = 0; 0.025; 0.125) ceramics have been obtained by a conventional method. A single-phase perovskite structure of the ceramics was identified by the X-ray diffraction method. EDS analysis, performed for the individual grains of the tested sample, showed a good homogeneous distribution of all elements throughout the grains. The thermal behaviour of BaZrxTi1-xO3 (x = 0; 0.025; 0.125) ceramics was studied using the Differential Scanning Calorimetry (DSC). Measurements showed the influence of Zr addition on the character of phase transition in the BaTiO3 structure. The results were compared with these ones obtained for pure BaTiO3.

Structural Characteristics of (Ba0.94Gd0.06)(Ti0.97Mg0.03)O3 in Cubic Structure Determined by High-Energy Synchrotron-Radiation Powder Diffraction

Structural study by high-energy synchrotron-radiation powder diffraction has been performed for (Ba0.94Gd0.06)(Ti0.97Mg0.03)O3 (BGTM) at 473 K to investigate the substitution effects of Gd and Mg on the cubic structure of BaTiO3. Our precise electron-density analysis using the maximum entropy method (MEM)/Rietveld method demonstrates that the bonding electron density between the Ti and O atoms in BGTM decreases with the substitution of Gd and Mg elements, which provides a significant contrast to the fact that the Ti–O bond length is shortened in BGTM. No obvious change is observed on the Ba–O ionic bonding. It is considered that the lowering of the cubic–tetragonal phase transition temperature in BGTM is attributed to the decrease in covalency on the Ti–O bond in BGTM. The features of thermal motions of the constituent atoms are discussed on the basis of the mean square thermal displacement parameters by taking account of the chemical bonding nature and tolerance factor of the BaTiO3 system.

Chemisorption of water and carbon dioxide on nanostructured BaTiO3–SrTiO3(001) surfaces

The interaction of water and carbon dioxide with nanostructured epitaxial (Ba,Sr)TiO3(001) thin film and bulk single crystal SrTiO3(001) surfaces was studied using x-ray photoemission spectroscopy (XPS), thermal desorption spectroscopy (TDS), and density functional theory (DFT). On both surfaces, XPS and TDS indicate D2O and CO2 chemisorb at room temperature with broad thermal desorption peaks (423–723 K) and a peak desorption temperature near 573 K. A comparison of thermal desorption Redhead activation energies to adsorption energies calculated using DFT indicates that defect surface sites are important for the observed strong adsorbate-surface reactivity. Numerical calculations of the competetive adsorption/desorption equilibria for H2O and CO2 on SrTiO3(001) surfaces show that for typical atmospheric concentrations of 0.038% carbon dioxide and 0.247% water vapor the surfaces are covered to a large extent with both adsorbates. The high desorption temperature indicates that these adsorbates have the potential to impact measurements of the electronic structure of BaTiO3–SrTiO3(001) surfaces exposed to air, or prepared in high vacuum deposition systems, as well as the electrical properties of thin film ATiO3-based devices.

Structural and ferroelectric properties of solid-state derived carbonate-free barium titanate (BaTiO 3) nanoscale particles

This work highlights the low-cost fabrication and characterization of perovskite BaTiO3 nanoscale particles. X-ray diffraction studies show that an insufficient reaction time at ∼800 °C will not result in the formation of the perovskite BaTiO3 structure, whereas over-sintering (∼900 °C) results in BaTiO3 and by-products of BaTi2O5. The polyvinyl alcohol polymer-dispersed nano-BaTiO3 system exhibits a proportionately large remanent polarization (∼1 μC cm−2) and coercive field (70 kV cm−1). The inexpensive synthesis is attractive for large-scale production and device application.

Local atomic structure of niobates and titanates from X-ray absorption spectroscopic data

The local atomic structure of PbTiO3, BaTiO3, and KNbO3 perovskite-type crystals and K x Na1 − x NbO3 solid solutions in different phases is investigated using the angular dependence of the pre-edge structure of the Ti and Nb K X-ray absorption spectra and the EXAFS data. In noncubic phases, a considerable deviation of the local structure from the structure determined from diffraction data is observed only for the tetragonal phase of the BaTiO3 crystal. It is revealed that, in the cubic phase of niobates, the niobium atoms are characterized by significant displacements from the centrosymmetric positions along the threefold axes, so that they are close in the magnitude and the direction to the displacements in the low-temperatures rhombohedral phases.

Domain structures of BaTiO3 in epitaxial BaTiO3/(NiFe2O4/BaTiO3)m/SrTiO3 multilayer films

BaTiO3/(NiFe2O4/BaTiO3)m/SrTiO3 (m = 1, 2, 3, 4) epitaxial heterostructures were fabricated on (0 0 1)-SrTiO3 substrates by employing the pulsed-laser deposition technique. Crystallographic characteristics of these multilayered composite films such as lattice constants, c/a ratio of tetragonal unit cell and the fraction of c-domain with the c-axis of the tetragonal unit cell parallel to the substrate normal direction or degree of c-axis orientation were evaluated. The coexistence of c- and a-domains with the c-axis of the tetragonal unit cell perpendicular to the substrate normal direction in these heterostructures was verified by the {3 0 3} asymmetric rocking curve measurement.