BaTiO3 Nanopowders Research Articles

Structural Details of BaTiO3 Nano-Powders Deduced from the Anisotropic XRD Peak Broadening.

In this study, nano-BaTiO3 (BTO) powders were obtained via the solvothermal method at different reaction times and were investigated using transmission electron microscopy (TEM), X-ray diffraction (XRD) and Raman spectroscopy. The results were compared with those obtained for a larger crystallite size BTO powder (BTO-m). The sizes of the cuboid crystallites (as determined by XRD and TEM) ranged from about 18 to 24 nm, depending on the reaction time. The evolution with temperature of the structure parameters of nano-BTO was monitored by means of X-ray diffraction and Raman spectroscopy and no signs of phase transition were found up to 170 °C. Careful monitoring of the dependence of the XRD peak widths on the hkl indices showed that the effect of the cubic crystallite shape upon the XRD peak widths was buried by the effect of hidden tetragonal line splits and by anisotropic microstrain. The good correlation of the line widths with the tetragonal split amplitudes, observed especially for BTO-m above the transition temperature, indicates tetragonal deformations, as also revealed by Raman spectroscopy. The large anisotropic microstrain shown by the nano-powders, which had a maximum value in the <100> directions, was considered evidence of the phenomenon of surface relaxation of cubic crystallites edged by {100} faces. The observed behavior of the nano-BTO structures with increasing temperature may suggest a correlation between the surface relaxation and tetragonal deformation in the nano-cubes. The experimental results for both nano-BTO and mezoscale-BTO are in agreement with the core-shell model.

Dielectric Properties of BaTiO3-Epoxy Nanocomposites in the Microwave Regime.

We synthesized BaTiO3–epoxy nanocomposites (particle size < 100 nm) with volume fractions up to 25 vol. %, whose high-frequency complex permittivity was characterized from 8.2 to 12.5 GHz. The maximum dielectric constant approaches 9.499 with an acceptable loss tangent of 0.113. The dielectric loss gradually saturates when the particle concentration is higher than 15 vol. %. This special feature is an important key to realizing high-k and low-loss nanocomposites. By comparing the theoretical predictions and the experimental data, four applicable effective-medium models are suggested. The retrieved dielectric constant (loss tangent) of 100-nm BaTiO3 nanopowder is in the range of 50–90 (0.1–0.15) at 8.2–12.5 GHz, exhibiting weak frequency dispersion. Two multilayer microwave devices—total reflection and antireflection coatings—are designed based on the fabricated nanocomposites. Both devices show good performance and allow broadband operation.

Enhanced electrocaloric effect within a broad temperature range in lead-free polymer composite films by blending the rare-earth doped BaTiO3 nanopowders

Enhanced electrocaloric effect within a broad temperature range in lead-free polymer composite films by blending the rare-earth doped BaTiO3 nanopowders

BaTiO3 films for multilayer devices by tape casting

The diversity of the applicational scope of modern printed electronics relentlessly requires the improvement of operational properties simultaneously with reducing the overall dimensions of devices. One of the most effective ways to overcome this major obstacle is the reduction of functional layers thickness in respect to the size of the device. In the present article, we are discussing a simple way of practical implementation of miniaturization concept through the application of a well-known high-productive industrial method of tape casting for obtaining thin nanostructured ceramic layers based on BaTiO3 nanopowders for MLCC. Using of nanosized powders per se imply a new approach of developing suspensions with suitable rheology for tape casting. We demonstrate, that a length of polymer molecule defines the size of floccules and therefore influences the thickness and surface quality of tape casted films. A certain nanopowder/polymer ratio contributes to the formation of the tapes with the surface roughness comparable with the size of one nanoparticle (20-25 nm). Moreover, it was established that developed suspensions are extremely sensitive to temperature changes. Lowering the temperature significantly affects the flow character of suspension and thus the thickness of casted tapes. Considering this fact, we propose an effective self-developed pre-cooling method of nanopowder suspension casting, which allows obtaining extremely thin and smooth tapes with a thickness of less than 1 µm and surface roughness of 20–25 nm by tape casting method.

Hydrothermal synthesis of tetragonal barium titanate nanopowders under moderate conditions

Monodispersed tetragonal barium titanate (BaTiO3) nanopowders were synthesized by a convenient hydrothermal route at a low temperature of 200?C in only 24 h. The key point of this method is to promote the generation of ultrafine titanium hydroxide precipitation precursors with the help of absolute ethyl alcohol and ammonia solution during the hydrolysis of Ti(OC4H9)4. The results of X-ray diffraction and Raman spectra show that the as-prepared BaTiO3 nanopowders possess tetragonal-dominant structure. The synthesized tetragonal BaTiO3 nanopowders exhibit relatively uniform size and good dispersity, with the average particle size of 96.1 nm and a tetragonality of 1.0073, which enable broad application prospects in the field of multilayer ceramic capacitors.

Green Synthesis of Ba1−Sr TiO3 ceramic nanopowders by sol-gel combustion method using lemon juice as a fuel: Tailoring of Microstructure, ferroelectric, dielectric and electrical properties

Abstract This article represents a simple, economic and low-temperature green combustion synthesis of Ba1−xSrxTiO3 (BST) ceramic nanopowders for composition x = 0.0, 0.2, 0.4, 0.6, 0.8 and 1.0 with lemon juice as a firing agent. The fabricated nanopowders were characterized by TGA/DSC, XRD, FTIR, FESEM, TEM etc. analytical techniques. XRD analysis reveals the formation of single-phasic tetragonal perovskite structure with no impurity phases for x = 0.0 to 0.2 samples. However, cubic phase was appeared for x = 0.4 to 1.0 samples. FTIR spectroscopic study evidenced the formation of perovskite structure by demonstrating a noticeable band in between 400 and 750 cm−1. The Scherrer and Williamson-Hall (W–H) analysis was utilized to evaluate the crystallite size. TEM study showed that, spherical shaped and uniform nanocrystalline powders (23–28 nm) were fruitfully synthesized. The saturation electric polarization (Ps), remanence polarization (Pr) and coercive field (Ec) decreases with increase in Sr2+ content expected to be dependent on the creation of oxygen vacancies and occurrence of cubic polymorphs by doping of Sr2+ ions. The ideal ferroelectric characteristics were obtained Ps = 5.6661 μC/cm2 and Ec = 2.1242 kV for pristine BaTiO3 sample. Dielectric constant (e’) was obtained at room temperature as a function of frequency, which shows exponential decay with the increase of frequency. The Maxwell-Wagner polarization and dipole polarization were existing in the Sr2+-substituted BaTiO3 nanopowders and were responsible for the obtained dielectric properties. The variation of DC-electrical resistivity (log ρ) versus temperature (300 K–833 K) was observed to be decreased with increasing temperature and Sr2+ substitution; demonstrating that an electrical energy transfer was a thermally stimulated procedure. The Sr2+-substitution has brought an overall enhancement in dielectric and electrical properties. However, the ferroelectric characteristics are weakened, which is primarily attributed to a considerable variation in the micro-structure of the solid.

Synthesis of tetragonal BaTiO3 nano-particle via a novel tartaric acid co-precipitation process

A novel tartaric acid co-precipitation process was firstly reported to prepare tetragonal BaTiO3 nano-powder with barium chloride, titanium tetrachloride as raw materials and tartaric acid as precipitant agent. The as-obtained BaTiO3 powder exhibited a small average particle size about 140 nm, which still held a high tetragonality (c/a ratio) of 1.0092, suggesting its promising applications in multilayer ceramic capacitors (MLCC). In addition, this synthetic method will be of general interest to people who focuses on synthesis technology of Ti-based multicomponent oxides nano-materials owing to its outstanding advantages, including mild reaction condition, facile synthetic processes and especially stabilization of (TiO)2+ even in a high pH about 8.

A new strategy to achieve the controllable preparation of nanoceramics with BaTiO3@resin core–shell nanoparticles

In this paper, phenolic resin (PR) is coated on the monodispersed BaTiO3 nanopowders (C-BTO) prepared by the co-precipitation method via a core–shell manner. This PR can optimize nanopowders’ dispersibility in the granulation, and act as a grain growth inhibitor during sintering. So BaTiO3 nanoceramics with dense and size-controlled morphology were achieved at a low sintering temperature. The microstructural and dielectric studies show that the grain size and dielectric properties initially increase and then decrease as the amount of PR increases. Moreover, the activation of PR is optimal at 20 wt%, and obtained ceramics have a high density and uniform grain size, with a relatively high dielectric constant (ɛmax) of 3545 and low dielectric loss (tanδ) of 0.011. Besides, by tailoring the particle size of C-BTO@PR powders, dense BaTiO3 ceramics with mean size of 135–308 nm can be obtained with sizes similar to initial particle. The results demonstrate that PR coated BaTiO3 nanopowders in core–shell structure is an effective strategy to prepare BaTiO3 nanoceramics controllably.

Study on the effect of Bi dopant on the structural and optical properties of BaTiO3 nanoceramics synthesized via sol-gel method

In this study the preparation of pure and Bismuth (Bi) doped barium titanate (BaTiO3) nanoceramics by sol-gel process is reported. The structural and optical properties of the samples were investigated using X-ray diffraction (XRD) and UV-visible spectroscopy. XRD results show that the samples are crystallized in the pure perovskite structure when calcined at relatively low temperature (800 °C) for 3 h, without the presence of secondary phases. Both Bi doping (1%, 2%) decrease the lattice parameters, tetragonality and the crystallite size. The decrease of their sizes can be explained by the replacement of large ionic radii of Ba2+ (1.35Å) ion by smaller ionic radii Bi3+ (1.03 Å) ion. A close investigation of the results shows that BT is a tetragonal-phase ferroelectric. The band gap of the Bi-doped BaTiO3 nanopowders is lower compared to that of pure BaTiO3, as determined from the analysis of UV absorbance spectra.

Structure and Dielectric Studies of Sn4+/Er3+ co-doped BaTiO3 Nano-Powders

Structure and Dielectric Studies of Sn⁴⁺/Er³⁺ co-doped BaTiO₃ Nano-Powders

The role of diffusion behavior on the formation and evolution of the core‐shell structure in BaTiO3‐based ceramics

AbstractIn this work, the influence of starting particle size and sintering conditions on the microstructures and dielectric properties of BaTiO3‐based ceramics coated with 0.3Bi(Zn1/2Ti1/2)O3‐0.7BaTiO3 were investigated to reveal the core‐shell structure by using high resolution transmission electron microscopy technique coupled with energy‐dispersive spectrometer analysis. The ion‐diffusion behavior plays a critical role in the formation and evolution of the core‐shell structure and, therefore, significantly influences the dielectric properties. When using starting powders containing BaTiO3 particles larger than 100 nm in size and sintering for shorter dwelling times (0.5‐2.0 hours), a core‐shell structure could be formed and retained owing to the limited diffusion behavior, enabling BaTiO3‐based ceramics to meet the X8R specification for multilayer ceramic capacitors applications at high temperatures. However, when using 80 nm BaTiO3 nanopowders and further extending the dwelling time to 6.0 hours, more driving energy was provided to prompt ion diffusion, which led to the compositional inhomogeneity becoming homogenized.

Influence of tin (IV) doping on structural and optical properties of rhombohedral barium titanate (BaTiO3)

The impact of tin (IV-Sn4+) doping into rhombohedral barium titanate (BaTiO3) towards the enhancement of second harmonic generation (SHG) was studied. XRD analysis confirms retention of rhombohedral symmetry in Sn4+ doped BaTiO3. UV-Vis absorption study reveals that Sn4+ doping has no significant effect on the optical band gap of BaTiO3. Raman spectrum portrays that undoped and Sn4+ doped BaTiO3 nanopowder exhibits Raman active modes of rhombohedral symmetry. The studies displays that Sn4+ doped BaTiO3 has created non-centrosymmetry, which could be utilized for enhancement in SHG and possibility to improve the efficiency in rhombohedral BaTiO3 based solar cells.

High-Performance Hybridized Composited-Based Piezoelectric and Triboelectric Nanogenerators Based on BaTiO3/PDMS Composite Film Modified with Ti0.8O2 Nanosheets and Silver Nanopowders Cofillers

In order to commercialize the rapidly developing technology of energy harvesters, the following devices need to be developed further for enhancing output performance, flexibility, scalability, facile fabrication, and cheaper price. The composite-based triboelectric nanogenerator (CTENG), which contains the above properties, is a promising technology that has attracted special interest for a decade. Focus has been placed on the hybrid concept between the composite-based piezoelectric nanogenerator (CPENG) and CTENG in order to enhance CTENG efficiency. This study presented a high-performance hybridized CPENG and CTENG device, which operated from the composite film of Ti0.8O2 nanosheets (Ti NSs)/silver nanoparticles (Ag NPs) co-doped BaTiO3 nanopowders (BT NPOs) inside the polydimethylsiloxane (PDMS) host. The 0.3 vol % of Ti NSs and 1.5 vol % of Ag NPs exhibited the optimum harvesting performance in all compositions, with an output voltage and current density reaching approximately 150 V and 0.32 μA/cm2, r...

Ferroelectric Fe–Cr Codoped BaTiO3 Nanoparticles for the Photocatalytic Oxidation of Azo Dyes

Ferroelectric Fe3+Cr3+ codoped BaTiO3 nanopowders have been successfully synthesized by a microwave-assisted hydrothermal method. The results indicate that by molar adjustment of the cations the ap...

Synthesis of bulk BaTiO3 aerogel and characterization of photocatalytic properties

BaTiO3 aerogels with a photocatalytic property were synthesized from metal barium via nanoparticle assembly method combined with ethanol supercritical drying technology. The specific surface area of the BaTiO3 aerogel could reach up to 233.24 m2/g, and the average pore size and total pore volume were 26.1 nm and 3.50 cm3/g, respectively. The sample showed excellent adsorption capacity and photocatalytic performance for 10 mg/L methyl orange solution (pH = 3), and the degradation rate reached up to 92.59% in 2 h, which was superior to BaTiO3 nanopowder. Moreover, the photodegradation rate was still about 80% after five-cycle experiments.

Structural, spectroscopic and dielectric properties of Ca-doped BaTiO3

Ca-doped barium titanate BaTiO3 nanopowders were synthesized by the sol–gel process using barium acetate [Ba(CH3COO)2], calcium acetate [Ca(CH3COO)2] and titanium butoxide [Ti(OC4H9)4] as precursors. This method was adopted because it allows obtaining powders of high purity, chemical homogeneity and fine particle size, and crystallization is possible at very low temperatures (800 °C) compared to that used by the conventional solid-state reaction method. In this study, the characterization of nanopowders and ceramics using X-ray diffraction (XRD), scanning electron microscopy (SEM), photoluminescence (PL), dielectric measurements, FTIR and Raman spectroscopy is carried out. The results revealed that the calcium ion incorporation had significant effect on structural and dielectric properties of barium titanate BaTiO3 (BT). XRD patterns suggested that nanopowders calcined at the temperature of 800 °C during 2 h could be crystallized into perovskite structure, with an average crystallite size in the range of 19.89–25.04 nm. Furthermore, it was observed that the Ca concentration variation affected the emission process with little displacement in the peak position. These results proved the optical band gap reduction by the presence of inter-band electron levels. Finally, the dielectric properties of the prepared samples were measured, revealing that the dielectric permittivity decreased with frequency increase, and the grain size and Curie temperature of the Ba1−xCaxTiO3 (BCT) ceramics sintered at 1200 °C were greatly affected by Ca substitution.

Magnetoelectric effect in magnetostrictive-piezoelectric composites containing magnetite nanoparticles

We report the use of nanoparticle (NP) magnetite, Fe3O4, in magnetostrictive-piezoelectric composites in trilayer laminate and single layer form. The magnetoelectric (ME) effect in both structures is highly anisotropic and linear up to 9 kOe. A trilayer laminated Fe3O4-NPs/PZT/Fe3O4-NPs composite displays the highest dc magnetic field response sensitivity, with dVME,ac/dHdc reaching 42 nV/Oe at a resonance frequency of 19.43 kHz. A slightly lower dVME,ac/dHdc of 35 nV/Oe is found for a single layer mixed composite containing Fe3O4 nanoparticles and BaTiO3 nanopowder at a resonance frequency of 0.4 kHz. The lowest ME response is observed for a single layer composite that had Fe3O4 nanoparticles and PZT powder where dVME,ac/dHdc is 1.4 nV/Oe at resonance (0.335 kHz). Our results show that composites containing Fe3O4 nanoparticles have potential applications that include wide magnetic field range vector magnetic field sensors – parallel magnetic field sensing using a trilayer configuration and perpendicular magnetic field sensing using a single layer configuration.

Sensing properties of barium titanate nanoceramics tailored by doping and microstructure control

BaTiO3 nanopowders doped with La and co-doped with La/Mn were prepared by auto-combustion and Pechini methods, respectively. The influence of the synthesis methods, dopants and sintering temperature on the BaTiO3 structure and its potential to be used as humidity and/or H2 gas sensor were studied. The optimization of all process parameters was performed to obtain adequate microstructure for the development of good sensor properties. The difference in the grain size between the La-doped and La/Mn co-doped samples and the formation of different types of defect structures in these ceramics were found to be significant for the desired electrical and ferroelectric properties. The La-doped ceramics with a pseudo-cubic structure showed the highest potential for gas sensors. The materials obtained by the Pechini method had a tetragonal structure and showed the best response, i.e., the change in electrical resistivity by four orders of magnitude in the humid atmosphere.

Nano-BaTiO3 phase transition behavior in coated BaTiO3-based dielectric ceramics

In this work, the phase structure of BaTiO3 nanopowders produced by the alkoxide-hydroxide and the hydrothermal method, respectively, was systemically investigated. BaTiO3 nanopowders with cubic phase produced by the alkoxide-hydroxide method could transform to tetragonal phase when heated to about 1100 °C. Cubic to tetragonal phase transformation behavior of BaTiO3 nanopowders coated with 0.3BZT-0.7BT or 0.03Nb2O5-0.01Co2O3 was studied. The internal stress within core-shell structure was proposed to explain the BaTiO3 phase transformation behaviors. The mismatch of thermal expansion coefficient between core and shell plays a crucial role in cubic to tetragonal phase transformation of BaTiO3. By tuning the composition of shell and the ratio of the shell to the core, the cubic BaTiO3 core can transform to tetragonal phase successfully after sintering at 1100 °C in BaTiO3 based ceramics with core-shell structure and it is mainly resulted by the reduced internal stress between the shell and core.

(Ba Ca)TiO3 nanopowder: Synthesis and their electrical and biological characteristics

Abstract Despite the applicable piezoelectric property of BaTiO3 (BT), its biomedical applications have been limited due to its weak bioactivity and osteoconductivity. To overcome these issues, in the present study, (BaxCa1-x)TiO3 (x = 1, 0.9, 0.8, 0.6, and 0) nanopowders were synthesized using a combination of sol-gel and mechanical activation processes. The changes in the chemical, electrical, structural and biological properties of BaTiO3, as a result of the substitution of Ba2+ with Ca+2 ions, were thoroughly studied. Substitution of Ba2+ with Ca2+ in the host (BaxCa1-x)TiO3 lattice changed the cubic structure of pure BT to tetragonal mode. Moreover, 40 at. % Ca2+ substitution in BT nanopowder ((Ba0.6Ca0.4)TiO3) resulted in decreased crystallite and particle size and reduced dielectric constant. In addition, bioactivity of (BaxCa1-x)TiO3 powder enhanced with increasing calcium content. MTT assay showed that 20 at.% Ca2+ substitution in the BT nanopowder resulted in significant increase in MG63 cell proliferation. Overall, calcium-substituted BT nanopowder could be a suitable candidate for bone repair.