All-inkjet-printed Metal-Insulator-Metal (MIM) capacitor

BaTiO₃-resin hybrid composite is one of the most promising candidates to surmount the intrinsic process issues of pure ceramic materials such as the requirement of high temperature sintering, disability to be integrated with dissimilar materials, etc. We utilized the inkjet printing to prepare all-inkjet-printed MIM (Ag/BaTiO₃-resin hybrid film/Ag) capacitor. The microstructures of the MIM capacitor were investigated to confirm the integrity of dissimilar layers within MIM capacitor. The dielectric properties of BaTiO₃-resin hybrid film in MIM capacitor were also investigated by measuring its relative permittivity and loss tangent. The inkjet-printed BaTiO₃-resin hybrid composite film showed that its relative permittivity and loss tangent were 70 and 0.011 at 1 MHz, respectively.     

界面极化注极聚丙烯薄膜驻极体的电荷存储特性研究

本文报道一种基于双层介质界面极化机理的新型驻极体注极技术: 借助辅助层对PP薄膜进行注极. 采用表面电位测试方法考察了注极温度、注极电压对所获PP薄膜驻极体电荷存储性能的影响, 并利用热刺激放电技术研究了其高温电荷存储性能, 同时测试了PP薄膜驻极体在X和Y方向的静电场分布. 结果表明: 界面极化注极是一种比电晕注极更为优异的驻极体形成方法. 在一定温度下, 驻极体表面电位随注极电压的增加而增加, 而且两者呈线性关系, 这一结果与注极过程的电荷积聚方程的分析完全一致. 注极温度的影响研究表明, 在保持注极电压不变(注极电压范围为0.5–3.0 kV)的情况下, 温度低于75 ℃时, 温度的变化对于注极效果的影响不明显; 当注极温度大于75 ℃ 时, PP薄膜驻极体的表面电位随注极温度的增加而增加. 表面电位随时间的变化研究表明, PP薄膜驻极体具有良好的电荷存储稳定性. 对其表面电位分布的测试表明, 界面极化注极所形成的PP薄膜驻极体呈现均匀的静电场分布.     

Synthesis of transparent BaTiO3 nanoparticle/polymer composite film using DC field

Transparent BaTiO₃ nanoparticle/polymer composite films were synthesized from titanium-organic film and barium ion in aqueous solution under direct current (DC) field. Titanium-organic precursor was synthesized from titanium isopropoxide, acetylacetone and methacrylate derivative. The UV treatment was effective to increase the anti-solubility of the titanium-organic film during DC processing. BaTiO₃ nanoparticles were crystallized in the precursor films on stainless substrates without high temperature process, as low as 40°C. The crystallite size of BaTiO₃ increased with increasing reaction temperature from 40 to 50 °C at 3.0 V/cm. BaTiO₃ nanoparticles also grew in size with increasing reaction time from 15 min to 45 min at 3.0 V/cm and 50 °C. Transparent BaTiO₃ nanoparticle/polymer films were synthesized on stainless substrates at 3.0 V/cm and 50°C for 45 min.     

Transport, structural and thermal studies on nanocomposite polymer blend electrolytes for Li-ion battery applications

Nanocomposite polymer electrolytes (NCPEs) composed of poly(vinylidenefluoride-co-hexafluoropropylene) (PVdF-co-HFP) as a host polymer, Poly(vinyl acetate) (PVAc) as an additive, Ethylene Carbonate (EC) as a plasticizer, Lithium Perchlorate as dopant salt and Barium Titanate (BaTiO₃) as a filler were prepared for various concentrations of BaTiO₃ using solvent casting technique. Thermal stability of the sample having maximum ionic conductivity was found using TG/DTA analysis. Nano composite polymer electrolytes were subjected to ac impedance analysis spectra for acquiring the ionic conductivity values at different temperature. Surface structure of the sample was analysed using scanning electron microscope and the complexations of samples were analysed using X-ray diffraction analysis. It was noted that the polymer electrolyte contains 8 wt. % of BaTiO₃ showed maximum ionic conductivity than the other ratios of BaTiO₃.     

A novel NiO/BaTiO3 heterojunction for piezocatalytic water purification under ultrasonic vibration

This work designed and prepared a novel heterojunction composite NiO/BaTiO₃ through a method of photodeposition and used it in piezocatalytic dye removal for the first time. Results of the piezocatalytic test indicated that the NiO/BaTiO₃ composite presented superior efficiency and stability in the RhB degradation under the vibration of ultrasonic waves. The best NiO/BaTiO₃ sample synthesized under light irradiation for 2 h displayed an RhB degradation rate of 2.41 h⁻¹, which was 6.3 times faster than that of pure BaTiO₃. By optimizing the piezocatalytic reaction conditions, the degradation rate constant of NiO/BaTiO₃ can further reach 4.14 h⁻¹ A variety of systematic characterizations were executed to determine the reason for the excellent piezocatalytic performance of NiO/BaTiO₃. The band potentials of NiO and BaTiO₃ are found to coincide, and at their contact interface, they may create a type-II p-n heterojunction structure. Driven by the potential difference and the built-in electric field, piezoelectrically enriched charge carriers can migrate between NiO and BaTiO₃, resulting in improved efficiency in charge separation and an increase in the piezoelectric catalytic performance. This study may provide a potential composite catalyst and a promising idea for the design of highly efficient catalysts in the field of piezoelectric catalysis.     

Nanocrystalline oxide (Y2O3, Dy2O3, ZrO2, NiO) coatings on BaTiO3 submicron particles by precipitation

Nanocoatings (5–20 nm) of different compounds on fine BaTiO₃ particles were obtained by means of precipitation processes. Homogeneous and smooth shells of Y(OH)CO₃ and Dy(OH)CO₃ were grown from nitrate solutions in the presence of urea. An irregular coating consisting of zirconia nanoparticles was produced from zirconyl nitrate solution using ammonia as a precipitating agent after adsorption of a polymeric polyelectrolyte on the BaTiO₃ surface. Composite particles with a peculiar morphology were obtained by inducing heterogeneous nucleation and growth of Ni(OH)₂ lamellae on the BaTiO₃ surface. The different shells can be transformed in a nanocrystalline coating of the corresponding oxide (Y₂O₃, Dy₂O₃, ZrO₂, NiO) by calcination at moderate temperatures (400–700 °C). The overall results indicate that precipitation from solution represents a versatile process to grow a second-phase layer on the surface of BaTiO₃ particles. This approach can be used as an alternative to mechanical wet mixing for controlled doping of ferroelectric materials and for the fabrication of composite materials with specific geometry of the two-phase assembly.     

Nanoparticulate BaTiO<Subscript>3</Subscript> film produced by aerosol-type nanoparticle deposition

Aerosol-type nanoparticle deposition (NPD) is a magical method to form a dense electroceramic film with a fine, nanoscale structure on a substrate surface by depositing ceramic particles through a nozzle at room temperature. This film has the potential to be applied to various electronic, environmental, and energy devices. However, the deposition mechanism and the nanostructure in the film are not understood sufficiently. This study aimed at investigating the crystal structure of an NPD as-deposited film, and compared the crystal structures of the NPD as-deposited film, annealed film, and the raw powders consisting of particles with diameters of 200 and 50 nm, respectively, using barium titanium oxide (BaTiO₃). We found that the crystal in BaTiO₃ with a disordered phase due to the Ba displacement within the BaTiO₃ was responsible for the adhesion between the BaTiO₃ crystalline particles having a diameter of approximately 10 nm, as well as with the substrate.     

Dielectric and magnetic properties of low-temperature fired NiCuZn-BaTiO3 composites

The composition effects on the dielectric and magnetic properties of NiCuZn-BaTiO₃ composites fired at low temperature were investigated. The coexistence of perovskite BaTiO₃ and spinel ferrite phases in the composites were observed; no significant chemical reactions occurred between BaTiO₃ and NiCuZn ceramics during sintering. The nanosized BaTiO₃ powders favored a decrease in grain size. The saturation magnetization, remanent magnetization and real permeability continuously decreased with increasing BaTiO₃ content. And the real permittivity continuously increased with the BaTiO₃ content. The Q-factor (quality factor) exhibited relatively high values with 20-30 wt% BaTiO₃. All composite materials exhibited a low dielectric loss below 100 MHz. Synthetically considerations, the composites with 20-30 wt% BaTiO₃ could obtain relatively high real permeability and real permittivity values, and the magnetic and dielectric losses were relatively low, so they were the best candidates to produce LC-integrated chip elements.     

Electrical and dynamic mechanical behavior of BaTiO3/VGCF/LDPE composite

The electrical and dynamic mechanical behavior of barium titanate (BaTiO₃)/vapor-grown carbon fiber (VGCF)/Low Density Polyethylene (LDPE) composites has been studied. The measurement of electrical conductivity exhibits a lower percolation threshold and a more distinct two-stage percolation region, especially with a wide plateau between the two stages, for BaTiO₃/VGCF/LDPE composites compared to the two-component system of VGCF/LDPE. This can be attributed to increase of the effective concentration of VGCF and the obstruction of BaTiO₃ particles on VGCF networks. The dynamic mechanical spectra of BaTiO₃/VGCF/LDPE composites present a distinctive α relaxation region with its peak value nearly remaining constant at its high temperature side in contrast to the abrupt decrease of LDPE. Moreover, the loss factor in the α relaxation region reaches its largest value for the composite of 8 vol% VGCF content. This means that the piezo-damping effect really functions in BaTiO₃/VGCF/LDPE composites and only in certain conditions can this effect have practical significance. Further examination of the damping behavior in a different relaxation region demonstrates that the piezo-damping effect is directly related to the relaxation behavior of the polymeric matrix. Also, the piezo-damping effect is highly temperature and frequency dependent. The dielectric measurements suggest that, before the formation of a certain critical conducting state, the energy dissipation approach of the piezo-damping effect may be mainly determined by the interfacial polarization effect in the composite. Thus, it may be inferred that the piezo-damping effect also contributes to the dramatic increase of the loss factor at the high temperature side of the α relaxation peak for the BaTiO₃/LDPE composite and functions practically even if there is no presence of VGCF.     

Surface reaction characteristics at low temperature synthesis BaTiO3 particles by barium hydroxide aqueous solution and titanium tetraisopropoxide

Well-crystallized cubic phase BaTiO₃ particles were prepared by heating the mixture of barium hydroxide aqueous solution and titania derived from the hydrolysis of titanium isopropoxide (TTIP) at 328 K, 348 K or 368 K for 24 h. The morphology and size of obtained particles depended on the reaction temperature and the Ba(OH)₂/TTIP molar ratio. By the direct hydrolytic reaction of titanium tetraisopropoxide, the high surface area titania (TiO₂) was obtained. The surface adsorption characteristics of the titania particles had been studied with different electric charges OH⁻ ions or H⁺ ions. The formation mechanism and kinetics of BaTiO₃ were examined by measuring the concentration of [Ba²⁺] ions in the solution during the heating process. The experimental results showed that the heterogeneous nucleation of BaTiO₃ occurred on the titania surface, according to the Avrami's equation.     

Electrophoretic deposition of BaTiO3/CoFe2O4 multiferroic composite films

Electrophoretic deposition was utilized for preparation of BaTiO₃/CoFe₂O₄ multiferroic composite thick films on indium-tin oxide substrates. The suspensions for electrophoretic experiments were prepared by dispersing BaTiO₃ and CoFe₂O₄ nanoparticles with different molar ratios into solvents composed of ethanol and acetylacetone. Polyvinyl butyral was added to the suspensions in order to enhance the adhesion and strength of deposit and prevent cracking. The zeta potential values of BaTiO₃/CoFe₂O₄ suspensions were measured to be 26.4-36.9 mV. The experiment results showed that deposited films were obtained only when the applied electric field was larger than a certain critical value. XRD and SEM analysis depicted the presence of constituent phases in composite films. The percolation threshold of composite films was improved through dispersing ferromagnetic phase into ferroelectric phase. Therefore, the ferroelectric properties of composite thick films were maintained when the ferromagnetic properties were enhanced significantly with increasing CFO content.     

Dielectric and magnetoelectric properties of BaTiO3–CoMn0.2Fe1.8O4 particulate (0-3) multiferroic composites

Multiferroic properties of (x) CoMn_0.2Fe_1.8O₄–(1-x) BaTiO₃ particulate magnetoelectric (ME) composites with x = 0.1, 0.2, 0.3 M percentage was investigated. The CoMn_0.2Fe_1.8O₄ (CMFO) phase was synthesized by solution combustion route and BaTiO₃ (BT) phase was synthesized by wet chemical method. X-ray diffraction studies revealed the purity of constitute phases; confirmed the manifestation of CMFO and BT within the ME composite structure. The microstructural aspects were observed by using Fe-SEM; revealed the effect of constituent phases on the average grain size of the composites. The temperature dependent dielectric properties for BT exhibited the three anomalies associated to its crystallographic lattice structure change with temperature. Dielectric constant of the composite was found to be decreased with CMFO content. All the composite structures exhibited typical magnetic hysteresis nature at room temperature and showed linear effect on the saturation magnetization of the composite with CMFO content. The ME response was examined at room temperature with an ac magnetic field at 1 kHz, all the composite showed a sharp decreasing behavior of the ME voltage coefficient (α_ME) to an applied dc bias in low field region. The maximum α_ME factor of ～8.51 mV/cm Oe was observed for 10% CMFO–90% BT composition.     

Electromagnetic properties and microwave absorption properties of BaTiO3-carbonyl iron composite in S and C bands

BaTiO₃ powders are prepared by sol-gel method. The carbonyl iron powder is prepared via thermal decomposition of iron pentacarbonyl. Then BaTiO₃-carbonyl iron composite with different mixture ratios was prepared using the as-prepared material. The structure, morphology, and properties of the composites are characterized using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction, scanning electron microscopy (SEM), and a network analyzer. The complex permittivity and reflection loss of the composites have been measured at different microwave frequencies in S- and C-bands employing vector network analyzer model PNA 3629D vector. The effect of the mass ratio of BaTiO₃/carbonyl iron on the microwave loss properties of the composites is investigated. A possible microwave absorbing mechanism of BaTiO₃-carbonyl iron composite has been proposed. The BaTiO₃-carbonyl iron composite can find applications in suppression of electromagnetic interference, and reduction of radar signature.     

Enhanced low-field-magnetoresistance and electro-magnetic behavior of La0.7Sr0.3MnO3/BaTiO3 composites

We report the structural, magentoresistance and electro-magnetic properties of ferromagnet–ferroelectric–type (1−x)La_0.7Sr_0.3MnO₃/xBaTiO₃ (with x=0.0%, 3.0%, 6.0%, 12%, 15.0% and 18.0%, in wt%) composites fabricated through a solid-state reaction method combined with a high energy milling method. The insulator–metal transition temperature shifts to a lower temperature and resistivity increases while the feromagnetic–paramagnetic transition temperature remains almost unchanged with the increase of BaTiO₃ content. Magnetoresistance of the composites at an applied magnetic field H=3 kOe is enhanced in the wide temperature ranges with the introduction of BaTiO₃, which could be explained by the enhanced spin polarized tunneling effect induced by the introduction of BaTiO₃. The low-field magnetoresistance of the composite is analyzed in the light of a phenomenological model based on the spin polarized tunneling at the grain boundaries. Furthermore, the temperature dependence of resistivity for this series has been best-fitted by using the adiabatic small polaron and variable range hopping models. These models may be used to explain effect of BTO on the electronic transport properties on high temperature paramagnetic insulating region.     

Strongly enhanced pinning force density in YBCO–BaTiO3 nanocomposite superconductor

YBa₂Cu₃O_7−δ–BaTiO₃ (4 wt.%) (YBCO–BTO (4%)) composite bulk polycrystalline sample has been synthesized by solid state reaction method. The structure of composite sample has been investigated by X-ray diffraction and magnetization measurements were carried out using MPMS SQUID VSM. The superconducting transition temperature of the YBCO–BTO (4%) sample was similar to that of pure YBCO. The critical current density (J_c) for YBCO–BTO (4%) sample increases significantly as compared to pure YBCO sample. The enhancement of the critical current density in the YBCO–BTO (4%) sample has been attributed to the presence of BaTiO₃ nanoparticles acting as artificial pinning centres. The introduction of BaTiO₃ particles in YBCO increases pinning force density from 0.71 GN/m² to 1.41 GN/m² at 4 K and 0.33 MN/m² to 0.97 MN/m² at 77 K.     

Different temperature dependences of photorefractive parameters of Ce-doped and Rh-doped BaTiO3

eff and the electro-optic coefficient r₃₃ in Ce-doped and Rh-doped BaTiO₃ were determined by two-beam coupling measurements. It was found that the effective trap density N_eff of BaTiO₃:Ce increases whereas that of BaTiO₃:Rh decreases with increasing temperature. The electro-optic coefficient r₃₃ of both crystals increases with temperature. The photorefractive response times were also measured and found to decrease with different rates as temperature increases in the two crystals. The results were discussed by using the two-centre model for BaTiO₃:Ce and three-charge-state model for BaTiO₃:Rh. We found that the different temperature dependence of N_eff in the two crystals was due to the fact that the deep- and shallow-trap levels in BaTiO₃:Ce are caused by different impurity centres whereas those in BaTiO₃:Rh are caused by different charge states of the same impurity centre. Received: 16 July 1998/Revised version: 26 October 1998     

In Situ Charge Characterization of TiO<Subscript>2</Subscript> and Cu–TiO<Subscript>2</Subscript> Nanoparticles in a Flame Aerosol Reactor

Charge distribution characteristics were investigated for nanoparticles synthesized in a diffusion flame aerosol reactor. The nanoparticles considered were pristine TiO₂ and Cu–TiO₂, with Cu dopant concentrations ranging from 1 to 5 wt% with particle size from 25 to 60 nm. In situ measurements were conducted by integrating a tandem differential mobility analyzer (TDMA) experimental setup with the flame aerosol reactor. A charging model was used to identify the important parameters that govern the two charging mechanisms (diffusion and thermo-ionization) in the flame and their relative importance at different operating parameters. The results indicate that TiO₂ and Cu–TiO₂ nanoparticles carry single as well as double unit charges. The charged fraction depends on particle size as well as on dopant concentration. The charged fraction increased with increasing particle size and decreased with copper dopant concentration. Measured charged fractions were similar for both the polarities at different mobility diameters. Based on the flame operating parameters, the calculations indicate that diffusion charging is dominant in the flame, which is consistent with the experimental results.     

Synthesis and study of electroactive nanoparticles and their polymer composites for novel applications

Polymer ceramic composites using a polymer binder, nanosized BaTiO₃ and metal particles were developed for radiation shielding in the microwave region. From X-ray Diffraction (XRD) the crystallinity and nanosize of BaTiO₃ was confirmed in the composite. Interesting changes in Differential Scanning Calorimetry (DSC) were observed before and after ball milling of BaTiO₃. Shielding Efficiency (SE) of microwave radiation has been measured from transmitted fraction (TF) of electromagnetic waves (EM) at different frequencies. The changes in TF were assigned to reflection and absorption of EM waves in different composites.     

Raman scattering studies on nanocrystalline BaTiO3 Part II—consolidated polycrystalline ceramics

BaTiO₃ dense ceramics with different grain sizes from 5.6 µm down to 35 nm were thoroughly studied by Raman spectroscopy. The temperature characteristics of optical phonons were compared with those obtained for powders. The micrograined ceramic revealed the well‐known spectrum profiles and transitions, typical for bulk BaTiO₃. On the other hand, the Raman spectra obtained for a nanograined ceramic with an average grain size of 35 nm revealed a tetragonally distorted pure BaTiO₃ phase showing a diffused phase transition behaviour with respect to temperature. Abnormality of phonon damping characteristics for the nanograined ceramic was demonstrated through comparison with powders with various crystallite sizes and the micrograined ceramic. The Curie temperature of the nanograined ceramic was estimated to be 105 °C from the temperature characteristic of a sharp peak at 307 cm⁻¹, which is one of the most specific tetragonal features for bulk BaTiO₃. In the present study, local stabilization of the tetragonal phase in ultra‐fine grains was experimentally demonstrated from comparison between the Raman spectroscopic results for powders and ceramics prepared through microemulsion‐mediated synthesis. Rather long phonon mean free paths can exist even in such ultra‐fine grains, but the phonon characteristics originating from various grains are diffused mainly because of the effect of internal stress. Copyright © 2007 John Wiley & Sons, Ltd.     

X-Ray diffraction and Raman spectroscopy studies of superlattices BaTiO3/(Ba0.5,Sr0.5)TiO3/SrTiO3

The structural characteristics of the BaTiO₃/(Ba_0.5,Sr_0.5)TiO₃/SrTiO₃ superlattice on a (001) MgO substrate have been studied using X-ray diffraction. The modulation period and unit cell parameters of layers forming the superlattice have been measured. The sizes of coherent scattering regions and average microstrains in the direction perpendicular to the surface have been estimated. The obtained characteristics are compared to those of the two-layer BaTiO₃/(Ba_0.5,Sr_0.5)TiO₃ superlattice. The Raman spectra demonstrate a substantial shift of the soft E(TO) mode in the three-layer superlattice as compared to the position in the two-layer superlattice. The effects observed are associated with a substantial increase in the temperature of the phase transition of the three-layer superlattice to the paraelectric phase.