Barium Titanate Layer Research Articles

Breggovskie rezonansy v mul'tiferroidnom kristalle s dvoynoy nelineynost'yu

The influence of double (electrical and magnetic) nonlinearity on the Bragg resonances of the hybrid electromagnetic-spin waves in a multiferroic crystal has been theoretically and experimentally revealed. The multiferroic crystal consists of an yttrium iron garnet layer with a periodic system of grooves on the surface and a ferroelectric strontium–barium titanate layer. A dispersion relation for the hybrid waves is obtained, and the mechanism of formation of main and hybrid band gaps, namely, suppression bands, is revealed. It is shown that taking into account the magnetic nonlinearity leads to frequency rearrangement of both band gaps and taking into account the electrical nonlinearity leads to frequency rearrangement of only the hybrid band gap. In the general case, the effects of the electrical and magnetic nonlinearities on the hybrid band gap can be compensated.

Enhancement of Mechanical Properties of Multilayer Ceramic Capacitors through a BaTiO3/polydopamine Cover Layer.

To fabricate multilayer ceramic capacitors (MLCCs) that can withstand external impacts, technologies to achieve excellent adhesion and mechanical strength of the cover layer should be essentially developed. Low adhesion and strength of the cover layer can lead to delamination and cracks in the MLCC, respectively. In this study, we present a method for applying polydopamine (PDA), a mussel-inspired adhesive protein, for as robust cover layer on an MLCC. Barium titanate (BT) particles treated with PDA increase the dispersion stability of the BT/PDA slurry, preventing re-agglomeration of the particles and enhancing the adhesiveness and strength owing to the cohesive properties of PDA. Compared to the BT layer, the adhesion of the BT/PDA layer was significantly enhanced by 217%; consequently, the compression modulus of the BT/PDA cover layer increased by 29.4%. After firing, the N-doped graphitic PDA played an important role in producing an MLCC cover layer with increased hardness and toughness. Furthermore, the N-doped graphitic PDA with a hydrophobic surface forms tortuous moisture paths in the cover layer, preventing the degradation of insulation resistance of the MLCC.

Quality Enhancement of Fiber Optic Surface Plasmon Resonance Biosensor Consisting of Metal and Barium Titanate Layer by Using Aluminum Alloy in Medical Applications

Quality Enhancement of Fiber Optic Surface Plasmon Resonance Biosensor Consisting of Metal and Barium Titanate Layer by Using Aluminum Alloy in Medical Applications

Detection of glucose concentration using a surface plasmon resonance biosensor based on barium titanate layers and molybdenum disulphide sheets

Diabetes is rapidly becoming a serious and life-threatening disease. It affects 415 million persons worldwide and is a leading cause of death among those aged 20 to 59. It is essential to develop a rapid-detection, accurate and sensitive glucose detector. In this work, a biosensor based on surface plasmon resonance (SPR) is proposed theoretically for the detection of glucose concentration. To realize higher sensitivity, the proposed SPR sensor contains a barium titanate layer placed between the metal (Ag) thin film and the molybdenum disulphide layer. Barium titanate material shows notable dielectric properties, such as low loss and a high index of refraction. It is expected to give a large shift in the resonance angle caused by a tiny change in the analyte refractive index. By optimizing the thicknesses of barium titanate and Ag and the number of molybdenum disulphide layers, the proposed biosensor can exhibit an ultra-high sensitivity of 307.36 deg RIU−1. The extremely high sensitivity makes the proposed SPR-based biosensor encouraging to be used in many fields of biosensing.

Influence of misfit stresses on the dielectric permeability of ferroelectric superlattices BaTiO3/BaZrO3

Based on the temperature dependences of the dielectric constant and the tangent of the dielectric loss angle in an alternating electric field, the reasons for the increase in the temperature range of the existence of the ferroelectric phase and the increase in the dielectric response of the BaTiO3/BaZrO3 ferroelectric superlattices in comparison with the analogous characteristics of its individual components are discussed. The results of a significant increase in these characteristics for the superlattice under consideration are explained on the basis of the concept of elastic misfit stresses arising in different layers of the superlattice due to the mismatch of the sizes of the unit cells that make up the lattice of single-crystal layers. These stresses lead to the formation of longitudinal polarization in the layers of barium titanate BaTiO3 and to the related contribution of the transverse component of the dielectric tensor to the effective permeability of the superlattice in the direction normal to the plane of the layers. Simultaneously, the misfit stresses of the lattice layers cause the appearance of a ferroelectric phase transition in the barium zirconate BaZrO3 layers in the superlattice with the appearance of spontaneous polarization and an increase in the dielectric constant of this layer in the direction normal to the plane of the lattice layers. The increase in dielectric losses in the low-temperature region is explained by the motion of domain walls in the layers of barium zirconate. Along with the dielectric response, the deformations that arise in the layers of the BaTiO3/BaZrO3 ferroelectric superlattice extend the temperature interval of the existence of the polar state in the lattice layers by several hundred degrees compared to barium titanate.

Performance Analysis of SPR Sensor Based on Polymer-tipped Optical Fiber Coated with Barium Titanate Layer

In this paper, an optical fiber SPR sensor based on polymer-tipped optical fiber (PTOF) coated with a gold film and a Barium Titanate (BaTiO3) layer has been designed and analyzed by finite difference time-domain (FDTD) method. Three SPR dips are observed and the sensitivity is proved to be higher than the structure without BaTiO3. A novel measurement method based on sum-value and difference-value of two SPR dips is proposed. Compared with conventional measurement method based on single dip, the measurement based on sum-value can significantly improve the sensitivity and the measurement based on difference-value can effectively reduce the environmental influence.

Study of Surface Plasmon Resonance Sensor Based on Polymer-Tipped Optical Fiber With Barium Titanate Layer

In this article, an optical fiber SPR sensor based on polymer-tipped optical fiber (PTOF) coated with a gold film and a Barium Titanate (BaTiO3) layer has been designed and optimized by finite difference time-domain (FDTD) method. Three SPR dips are observed and the optimal sensitivity of single-mode PTOF SPR sensor coated with an additional BaTiO3 layer reaches 6710 nm/RIU when refractive index (RI) of analyte is 1.333–1.343. A novel measurement method based on sum-value and difference-value of two SPR dips is proposed. Compared with conventional measurement method based on single dip, the measurement based on sum-value can significantly improve the sensitivity and the measurement based on difference-value can effectively reduce the environmental influence.

Sensitivity enhancement of surface plasmon resonance biosensor based on graphene and barium titanate layers

A surface plasmon resonance-based biosensor, consisting prism, silver, barium titanate (BaTiO3) and graphene layers, is presented by using angular interrogation. The structure is specially designed to further enhance the sensitivity and to decrease the full width at half maximum (FWHM) thereby improving the sensor performance. Theoretical analysis shows that the highest sensitivity can reach at 257°/RIU where the thickness of Ag layer is 45 nm with 10 nm BaTiO3 and one graphene layer. Compared with existing biosensors, the proposed biosensor exhibits higher sensitivity, lower FWHM and two times better preformation in the quality factor of the sensor, which would make our design have more applications in the field of biosensors.

Forming Porous Structures on Silicon with a Ferroelectric for Capacitive Microelectronic and Microsystems Engineering Elements

The formation of heterostructures based on porous silicon with barium titanate for application in capacitive electronic and microsystem engineering elements has been experimentally investigated. The dependences of the capacitance and permittivity on the porous matrix dimensions, number of deposited barium titanate layers, and material of capacitor structure plates has been analyzed.

Piezoelectric Energy Harvesting Characteristics of Barium Titanate Based Composite Laminates under Cyclic Concentrated Loads

We investigate the dynamic electromechanical behavior in barium titanate (BT) based composite cantilevers under cyclic concentrated loads in a combined numerical and experimental approach. The laminated composite cantilever consists of the BT and copper (Cu) layers, and the BT layer has sensing and driving electrodes. The output voltage of the cantilevers due to cyclic bending were calculated by three dimensional finite element method. The output voltage was then measured, and numerical simulations were compared with test results to verify the finite element model. The influences of sensing electrode geometry and load resistance on the dynamic electromechanical fields were examined in detail.

Barium titanate coated and thermally reduced graphene oxide towards high dielectric constant and low loss of polymeric composites

Novel barium titanate (BT) layer coated and thermally reduced graphene oxide (TGO) hybrid sheets (BT@TGO) were successfully synthesized by a facile sol-gel method combining with thermal treatment process (600 °C) under nitrogen atmosphere. The BT precursors attached on graphene oxide (GO) sheets were crystallized into perovskite structure with high permittivity and GO sheets were thermally reduced heavily at such high temperature simultaneously. The hybrids were used as filler to fabricate high performance dielectric polyvinylidene fluoride (PVDF) composites by solution blending method and their dielectric performances were studied. It was found that addition of BT@TGO decreases the electrical conductivity when compared with TGO/PVDF composites and pure PVDF, and BT@TGO/PVDF composites exhibit not only high dielectric constant but also low dielectric loss. For instance, at 103 Hz, the dielectric constant of PVDF composites containing 8.0 wt% BT@TGO is up to ∼56.3 at room temperature, which is over 5 times than that of pure PVDF polymer (∼10.3). More importantly, the dielectric loss is suppressed and only 0.058, which should be attributed to the effective encapsulation of insulating BT layer with high permittivity on the TGO surface. In addition, the improved thermal stability and crystallization behavior of BT@TGO/PVDF composites were also investigated.

Piezoelectric Detection and Response Characteristics of Barium Titanate Unimorph Cantilevers Under AC Electric Fields

This paper studies the detection and response characteristics of barium titanate (BT) unimorph cantilevers under alternating current (AC) electric fields both numerically and experimentally. The unimorph cantilever consists of the BT layer and Cu shim, and the BT layer has sensing, grounding and driving electrodes. The deflection and output voltage of the cantilevers were predicted by three dimensional finite element analysis (FEA). The deflection and output voltage were also measured, and a comparison was made between prediction and experiment. The deflection, stress, output voltage and output power were then discussed.

OS1509-289 チタン酸バリウム積層材料の圧電振動発電・動的応答挙動

This paper studies the vibration energy harvest and response characteristics of poled barium titanate (BT) unimorph cantilevers both analytically and experimentally. The unimorph cantilever consists of the BT layer and Cu shim, and the BT layer has sensing, grounding and driving electrodes. The output voltage of the cantilever excited by bending vibration was predicted by three dimensional finite element analysis (FEA). The output voltage was also measured, and a comparison was made between prediction and experiment. The effects of sensing electrode geometry and load resistance on the dynamic electromechanical fields and output power were then discussed in detail.

Properties of BaTiO3/BaZrO3 ferroelectric superlattices with competing instabilities

Properties of (BaTiO$_3$)$_1$/(BaZrO$_3$)$_n$ ferroelectric superlattices (SLs) with $n = {}$1--7 grown in the [001] direction are calculated from first principles within the density functional theory. It is revealed that the quasi-two-dimensional ferroelectricity occurs in these SLs in the barium titanate layers with a thickness of one unit cell; the polarization is oriented in the layer plane and weakly interacts with the polarization in neighboring layers. The ferroelectric ordering energy and the height of the barrier separating different orientational states of polarization in these SLs are sufficiently large to provide the formation of an array of independent polarized planes at 300 K. The effect of the structural instability on the properties of SLs is considered. It is shown that the ground state is a result of simultaneous condensation of the $\Gamma_{15}$ polar phonon and phonons at the $M$ point (for SLs with even period) or at the $A$ point (for SLs with odd period); it is a polar structure with out-of-phase rotations of the octahedra in neighboring layers, in which highly polarized layers are spatially separated from the layers with strong rotations. The competition between the ferroelectric and structural instabilities in biaxially compressed SLs manifests itself in that the switching on of the octahedra rotations leads to an abrupt change of the polarization direction and can cause an improper ferroelectric phase transition to occur. It was shown that the experimentally observed $z$-component of polarization in the SLs can appear only as a result of the mechanical stress relaxation.

Ion beam synthesis and investigation of nanocomposite multiferroics based on barium titanate with 3d metal nanoparticles

Ni + ions with an energy of 40 keV into ferroelectric barium titanate plates to doses in the range (0.5–1.5) × 10 17 ions/cm 2 . It has been found that nanoparticles of metallic iron, cobalt, or nickel are formed in the bar� ium titanate layer subjected to ion bombardment. With an increase in the implantation dose, the implanted samples sequentially exhibit superparamagnetic, soft magnetic, and, finally, strong ferromagnetic properties (a)

Analysis and Characterization of Phase Evolution of Nanosized BaTiO3 Powder Synthesized Through a Chemically Modified Sol-Gel Process

In the current research, a cost-effective and modified method with a high degree of reproducibility was proposed for the preparation of fine nanoscale and high-purity BaTiO3. In contrast to the other established methods, in this research, carbonate-free BaTiO3 nanopowders were prepared at a lower temperature and in a shorter time span. To reach an in-depth understanding of the scientific basis of the proposed process, an in-detail analysis was carried out for characterization of nanoscale BaTiO3 particles via differential thermal analysis (DTA)/thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) techniques aided by theoretical calculations. The effects of the temperature and time of calcination process on the preparation mechanism, phase transformation, tetragonality, and particle size of BaTiO3 were examined. The reaction that results in the formation of barium titanate initiated at approximately 873 K (600 °C) and seemed to be completed at approximately 1073 K (800 °C) and the polymorphic transformation of cubic to tetragonal initiated at approximately 1173 K (900 °C). It seemed to be completed at approximately 1373 K (1100 °C). According to the reaction mechanism, the formation of BaTiO3 in the initial stage of the interfacial reaction between BaCO3 and TiO2 depends on the BaCO3 decomposition. In the second stage, the BaTiO3 formation is controlled by barium diffusion through the barium titanate layer. In this stage, in contrast to the literature, no secondary phase was detected. The overall characterizations showed the temperature is more effective than time on the progress in process of preparation because of its diffusion-controlled nature.

Microstructural and optical investigations of Ce-doped barium titanate thin films by FTIR and spectroscopic ellipsometry

(BaTiO3)1− x (CeO2) x (with x = 0, 1, 3, 5.7 and 16 at.%) thin films were prepared by electron beam evaporation method. According to X-ray diffraction, nanosized and amorphous Ce-doped barium titanate thin films were obtained. The crystallinity diminished as Ce content increased. The increase in the Ce slightly shifts the absorption peaks at 433–450 and 416–424 cm−1 to higher wavenumbers. A two-layer model was used to describe the experimental ellipsometric data. The Bruggeman effective medium approximation (BEMA) was used to describe the surface roughness layer and the Cauchy dispersion relation was used to describe the main Ce-doped barium titanate layer. The refractive index and the extinction coefficient were found to increase with increasing Ce content; however, the optical band gap decreased with increasing Ce content. The accurate determination of the optical constants of Ce-doped barium titanate thin films may favor them in the applications of optical thin film devices.

Magnetostrictive/electrostrictive fracture of the piezomagnetic and piezoelectric layers in a multiferroic composite: Anti-plane case

The main purpose of the present work is to study the influences of magnetostriction, electrostriction and piezomagnetic/piezoelectric stiffening on the fracture behavior of a layered multiferroic composite. For comparison, it is assumed that there is a crack, parallel to the interface, in each layer. Methods of cosine transform and Cauchy singular integral equations are used to solve the crack problem. Numerical results of the stress intensity factor (SIF) are provided and the computational accuracy is demonstrated. Discussion on the numerical results indicates that the multiferroic composite consisting of cobalt ferrite and barium titanate layers are more prone to fracture under electric loading than under magnetic loading. In the case of magnetostriction, to increase the shear modulus of the piezomagnetic layer would raise the SIF; but to increase that of the piezoelectric layer would reduce the SIF; in the case of electrostriction, inverse results are obtained. Piezomagnetic stiffening can affect the SIF when the composite is under electrostriction; piezoelectric stiffening can influence the SIF if the composite is under magnetostriction. In addition, it is also revealed that two parallel equal cracks may shield each other even if an interface exists between them.

Electrophoretic Deposition of CoFe2O4 Nanograins Dispersed in a Laser Ablated BaTiO3 Matrix

Thin film nanocomposites composed by CoFe2O4 grains, deposited by electrophoresis, and subsequently covered by a laser ablation deposited BaTiO3 layer, were prepared with different cobalt ferrite concentrations (x). The cobalt ferrite phase was under a compressive strain that relaxed as the CoFe2O4 concentration increased. Consequently, a blueshift of the Raman peaks of CoFe2O4 was observed, that decreased with increasing x. The dielectric permittivity of the films was found to decrease with increasing cobalt ferrite concentration, due to the decrease of the barium titanate layer grain size with increasing CoFe2O4 content in the films.

Selective laser sintering of barium titanate–polymer composite films

A selective laser sintering process has been used to consolidate electro-ceramic thin films on silicon substrates. Methods of forming pre-positioned layers of barium titanate were investigated by spin-coating the feedstock powder mixed with a commercial polymer photo-resist. The ceramic–polymer composite was deposited directly onto a nickel film which was evaporated onto a silicon substrate, pre-oxidised to form an electrically insulating layer. A range of laser processing parameters was identified in which consolidated barium titanate layers could be formed. The laser power was found to be more influential in forming sintered microstructures than laser exposure time. The microstructure of barium titanate films is sensitive to the SLS laser-processing conditions, with the optimum laser powers for the processing of the BaTiO3–polymer found to be in the range 17–20 W. This article highlights the possibility of using ‘direct write’ techniques to produce piezoelectric materials upon silicon substrates.