Ba0.5Sr0.5TiO3 Research Articles

Enhancement of energy density in novel Ba0.67Sr0.33TiO3 nanorod array nanocomposites

The majority of the previously reported nanocomposites obtainable with higher energy density (>15 J cm−3) relies strongly on much higher breakdown strength (>4000 kV cm−1). The operation of capacitors in such higher applied electric field brings challenges because of the substantially increased the failure probability. In this study we explored the dispersibility and the orientation of fillers in nanocomposites as they play vital roles in the energy density. Based on the infinite element modulation results, an original design of 1–3 type composite structure was employed in the current study. This design adopts the one-dimensional (110)-oriented monodispersed barium strontium titanate Ba0.67Sr0.33TiO3 (BST) nanorod array as fillers embedded in the three-dimensional poly (−vinylidene fluoride) (PVDF) polymer matrix. With these originally designed BST/PVDF nanocomposites, we have demonstrated a significant enhancement of energy density at a lower applied electric field. For example, an energy density of 13.10 J cm−3 at electric field of 3400 kV cm−1 can be obtained, an enhancement of 3 times larger than that of bare PVDF. Moreover, the discharge efficiency is maintained at 69% at 3400 kV cm−1. The high performance of this originally designed nanacomposite demonstrated its potential application in the next generation energy storage devices.

Observation of Phase Transitions of Ba0.6Sr0.4TiO3–Silicon Hybrid Metamaterial by THz Spectra

The ferroelectric thin film such as BaSrTiO3 (BST), exhibiting great tunable characteristics, is a hot spot in photonic devices for both microwave and terahertz frequencies. This report presents a ...

Terahertz wave modulation properties of thermally processed BST/PZT ferroelectric photonic crystals

BST ( Ba 0.5 Sr 0.5 TiO 3 ) / PZT ( Pb 0.52 Zr 0.48 TiO 3 ) photonic crystals were fabricated by magnetron sputtering and annealed at 620 ° C − 700 ° C . By controlling the crystallinity and the oxygen vacancies of the ferroelectric photonic crystals, the optically and electrically controllable terahertz wave modulations were realized. The variation in refractive index of the 680°C annealed sample showed the highest modulation to the optical pump and increased to 11.9 due to the highest absorption near 532 nm. In the optical pump, the electrons from Ti 3 + 2 p 3 / 2 ions could be stimulated and captured by Ti 4 + 2 p 3 / 2 ions, and the ratio of Ti 3 + / Ti 4 + observed increased with the increasing annealing temperature, indicating the increasing oxygen vacancies concentration, which increased the 532 nm optical absorption and contributed to the improved optical modulation. The excess Pb migrating to the surface at higher annealing temperature might be one reason for the degradation of optical modulation. The increasing polarization and leakage current could contribute to the increasing permittivity and loss with the increasing annealing temperature. Two different results were observed on the sample annealed at 680°C when the order of applying external optical and electric fields was changed, due to the different migration mechanisms of excited carriers. This work provides a potentially effective approach to fabricate THz sensing, imaging, and communications devices with multi-function in the modulation of optical and electric multi-fields.

Vacancy-induced resistive switching and synaptic behavior in flexible BST@Cf memristor crossbars

In this study, carbon fibers (Cf) coated with Ba0.6Sr0.4TiO3 (BST) (BST@Cf) were prepared by magnetron sputtering and subsequently heated in nitrogen to produce oxygen vacancies. BST@Cf and nitrogen-treated BST@Cf were cross-stacked on polyimide (PI) film to make a BST@Cf memristor. The electrical properties of BST@Cf memristor were measured after being bent 3000 times. The device exhibits bipolar figure-of-eight (f8) hysteresis loop characteristics under applied voltage. The hysteresis loops narrow with increasing temperature of heat treatment in nitrogen, due to decrease in oxygen vacancy concentration. The hysteresis loops demonstrate the switching process of resistance between high resistance state (HRS) and low resistance state (LRS), with a maximum HRS/LRS ratio of 106. The switching process can be divided into two parts, corresponding to Schottky Emission and Fowler-Nordheim (F–N) Tunneling. It is notable that no electroforming voltage is required to stimulate the memristor. The constructed memristor was cycled successfully 1000 times and retained the LRS 787 s during power cut off. In addition, the device exhibited synaptic behavior including learning and forgetting processes, in accordance with the paired-pulse facilitation (PPF) rule. The use of BST@Cf in the construction of the nonvolatile memristor imparts flexibility to the device allowing for the possibility of wearable flexible intelligent memristor based electronic devices in the future.

Influence of solid loading on densification behavior, micromorphology and dielectric properties of Ba0.67Sr0.33TiO3 ceramics fabricated by a novel DCC-HVCI method

Ba0.67Sr0.33TiO3 (BST) ceramics with highly improved dielectric performance were fabricated by a novel direct coagulation casting via high valence counter ions (DCC-HVCI) method. The influence of solid loading on densification behavior, micromorphology, and dielectric performance of the samples was investigated. With the increase of solid loading from 40 to 50 vol%, the maximum densification rate of BST ceramics increased from 0.090 to 0.122 s−1, and the densification temperature decreased from 1424 to 1343 °C, which indicated that high solid loading could promote the densification behavior of samples during sintering. BST ceramics fabricated by the DCC-HVCI method showed uniform grain size and microstructure, which was beneficial for the dielectric properties of BST ceramics. Samples obtained from 45 vol% suspensions possessed the lowest dielectric permittivity (εr ≈ 2801), and the dielectric loss (tanδ≈0.0262) was about 1/10 of that of dry-pressed samples (tanδ≈0.301), which could be attributed to the composition homogenization.

Polar nano-clusters in nominally paraelectric ceramics demonstrating high microwave tunability for wireless communication

Dielectric materials, with high tunability at microwave frequencies, are key components in the design of microwave communication systems. Dense Ba0.6Sr0.4TiO3 (BST) ceramics, with different grain sizes, were prepared in order to optimise the dielectric tunability via polar nano cluster effects. Dielectric permittivity and loss measurements were performed at both high and low frequencies and were supported by results from X-ray powder diffraction, scanning and transmission electron microscopies, Raman spectroscopy and piezoresponse force microscopy. The concentration of polar nano clusters, whose sizes are found to be in the range 20–50 nm, and the dielectric tunability increase with increasing grain size. A novel method for measurement of the microwave tunability in bulk dielectrics is presented. The highest tunability of 32 % is achieved in ceramics with an average grain size of 10 μm. The tunability of BST ceramics with applied DC field is demonstrated in a prototype small resonant antenna.

Mechanically controllable nonlinear dielectrics.

Strain-sensitive Ba x Sr1-x TiO3 perovskite systems are widely used because of their superior nonlinear dielectric behaviors. In this research, new heterostructures including paraelectric Ba0.5Sr0.5TiO3 (BSTO) and ferroelectric BaTiO3 (BTO) materials were epitaxially fabricated on flexible muscovite substrate. Through simple bending, the application of mechanical force can regulate the dielectric constant of BSTO from -77 to 36% and the channel current of BTO-based ferroelectric field effect transistor by two orders. The detailed mechanism was studied through the exploration of phase transition and determination of band structure. In addition, the phase-field simulations were implemented to provide theoretical support. This research opens a new avenue for mechanically controllable components based on high-quality oxide heteroepitaxy.

High energy density with ultrahigh discharging efficiency obtained in ceramic-polymer nanocomposites using a non-ferroelectric polar polymer as matrix

To overcome the low discharging efficiency of ceramic-polymer composites using ferroelectric polymers as matrix and to take the advantage in fabrication offered by the polar polymer, a polar but non-ferroelectric polymer – poly(methyl methacrylate) (PMMA) – was selected as the matrix in the development of high performance composites for energy storage. Ba0.5Sr0.5TiO3 (BST) nanoparticles were selected as the filler. Freestanding and flexible BST-PMMA ceramic-polymer nanocomposites with BST content up to 30 vol.% were fabricated in thickness of about 5 μm using spin-coating process and were systemically studied. Due to the strong interaction between the polar groups of PMMA and the hydroxyl groups on the surface of BST nanoparticles, the suspension of BST nanoparticles in PMMA solution exhibits excellent stability and, hence, the nanocomposite films have excellent microstructure uniformity and compatibility between the BST nanoparticles and PMMA matrix. All the BST-PMMA films exhibit excellent frequency (100 Hz to 1 MHz) and temperature (−90 to 100 °C) stabilities in their dielectric properties with a high energy-storage density of more than 11 J/cm3. Most importantly, an ultra-high discharging efficiency of almost 100% is obtained in all the nanocomposites.

Enhanced energy storage properties of fine-crystalline Ba0.4Sr0.6TiO3 ceramics by coating powders with B2O3–Al2O3–SiO2

A core–shell mixing technique was utilized to modify the Ba0.4Sr0.6TiO3 (BST)particles in order to obtain the fine-crystalline Ba0.4Sr0.6TiO3 ceramics and improve ceramics energy storage capability. Coating layers of (9B2O3–13Al2O3–78SiO2, mol%) (BAS)were deposited onto Ba0.4Sr0.6TiO3 nanoparticles by a sol-precipitation method. The microstructures, phase composition and dielectric properties were investigated. And fine-crystalline BST ceramics with an average grain size below 150 nm by coating BAS has been prepared. The dielectric breakdown strength and energy storage density significantly improved due to the addition of BAS. The maximum energy storage density obtained from coating 3 wt% BAS was 1.8 J/cm3 at 410 kV/cm, which was higher than pure BST ceramics. Thus, the core-shell architecture is an effective strategy to improve the energy storage performance.

Effect of volume fraction on magnetoelectric coupling effect of Co0.1Cu0.9Fe2O4/Ba0.8Sr0.2TiO3 composite liquid

Co0.1Cu0.9Fe2O4 (CCFO) and Ba0.8Sr0.2TiO3 (BST) particles were respectively prepared by chemical coprecipitation and hydrothermal method, then CCFO/BST composite liquid was synthesized by distributing surface modified CCFO and Ba0.8Sr0.2TiO3 particles into insulating silicone oil. Effects of volume fraction (ϕv = 1%, 2%, 5% and 10%) on the microstructure, dielectric, ferroelectric and magnetoelectric coupling effect were comparatively investigated. XRD showed that the pure phase of CCFO and BST particles was successfully prepared. CCFO/BST composite particle shows ferromagnetic behavior due to the contribution of magnetic phase CCFO. The dielectric constant of CCFO/BST composite liquid is about 1/25 of the composite particles, and the dielectric constant value of the composite liquid decreases with increasing the volume fraction because the permittivity of silicone oil is far smaller than that of CCFO/BST composite particles. The relative change of dielectric constant of composite liquid under the action of external magnetic field is greater than that of composite particle due to its mobility of particles in liquid. The values of remnant polarization (Pr), coercive field (Ec) and leakage current of CCFO/BST composite liquid increase monotonically with increasing volume fraction, while excessive volume fraction may result in abnormal phenomenon because of the agglomeration of particles. Magnetic field-induced chain structure of the composite liquid has been observed under a light microscope at a magnification of 200. The maximal magnetoelectric (ME) coupling coefficient is about 89.78 V/(cm Oe), which is obtained in the CCFO/BST composite liquid when the volume fraction is 10%.

Application of Ba0.5Sr0.5TiO3 (Bst) Film Doped with 0%, 2%, 4% and 6% Concentrations of RuO2 as an Arduino Nano-Based Bad Breath Sensor

Ba0.5Sr0.5TiO3 (BST) film doped with variations in RuO2 concentration (0%, 2%, 4%, and 6%) has been successfully grown on a type-p silicon substrate (100) using the chemical solution deposition (CSD) method and spin-coating at a speed of 3000 rpm for 30 s. The film on the substrate was then heated at 850 °C for 15 h. The sensitivity of BST film + RuO2 variations as a gas sensor were characterized. The sensitivity characterization was assisted by various electronic circuitry with the purpose of producing a sensor that is very sensitive to gas. The responses from the BST film + RuO2 variation were varied, depending on the concentration of the RuO2 dope. BST film doped with 6% RuO2 had a very good response to halitosis gases; therefore, this film was applied as the Arduino-Nano-based bad-breath detecting sensor. Before it was integrated with the microcontroller, the voltage output of the BST film was amplified using an op-amp circuit to make the voltage output from the BST film readable to the microcontroller. The changes in the voltage response were then shown on the prototype display. If the voltage output was ≤12.9 mV, the display would read “bad breath”. If the voltage output >42.1 mV, the display would read “fragrant”. If 12.9 mV < voltage output ≤ 42.1 mV, the display would read “normal”.

Polymerizable Ceramic Ink System for Thin Inkjet-Printed Dielectric Layers.

An innovative ceramic ink system for thin inkjet-printed dielectric layers is presented, with which it is possible to avoid undesired drying effects. This system contains surface-modified Ba0.6Sr0.4TiO3 (BST) particles, a cross-linking agent, and a thermal radical initiator. The polymerization starts immediately after the ink drop contacts the heated substrate and therefore leads to very homogeneous topographies. Since an organic/inorganic composite ink is used, no sintering is needed after printing and thus printing on flexible substrates is possible. A comparison of the printing and drying behavior between modified and nonmodified BST with the described ink system is performed. The successful surface modification is confirmed via X-ray photoelectron spectroscopy (XPS). Topographies of different printed structures are compared by white light interferometry, the occurring polymerization is confirmed by measurements with an oscillatory rheometer, layer thicknesses are determined by scanning electron microscopy (SEM) images, and the capacitance of a printed capacitor is measured via impedance spectroscopy. It is successfully shown that the developed ink system enables the production of thin ceramic layers (<1 μm) with very homogeneous topographies since undesired drying effects can be avoided. The printed dielectric layers on flexible substrates have a high ceramic content and a high permittivity of 40.

Investigation of Ba0.6Sr0.4TiO3 thick films by means of a novel THz-TDS approach

Ba0.6Sr0.4TiO3 (BST) ferroelectric thick films were grown on MgO(0 0 1) and Al2O3(0 0 0 1) single-crystal substrates by using a pulsed laser deposition method. Structural, morphological, optical, and terahertz characterization of the BST films were performed by X-ray Diffraction, Atomic Force Microscopy, Spectroscopic Ellipsometry (SE), and Terahertz Time-Domain Spectroscopy (THz-TDS). Single-phase samples with strong preferred (1 1 1) orientation and surface roughness lower than 1.5% of their thicknesses have been obtained for both types of substrates. SE was employed to extract the thickness and optical properties by using a 3-layer optical model (substrate/thin film/roughness). The inferred refractive index @630 nm is around 2.05, while the optical interference is visible until 3.3 eV. The THz-TDS measurements in transmission set-up were carried out one after the other on substrates before and after the BST film deposition. The standard THz-TDS analysis of double-layer samples proved difficult to complete in the cases in which a thin or thick film is deposited on a much thicker substrate of known dielectric properties. However, we have been able to extract the complex dielectric permittivity in the THz domain for BST samples with thicknesses of few microns, by developing a specific procedure of data analysis.

Improved energy storage properties of Mn and Y co-doped BST films

Ba0.67Sr0.33TiO3 (BST) thin film and Ba0.664Y0.006Sr0.33Ti0.995Mn0.005O3 (BYSTM) thin film were deposited on LaNiO3 (LNO)/SiO2/Si substrates by radio frequency magnetron sputtering. All films show polycrystalline with a perovskite structure. A compact, crack-free and uniform morphologies were observed. The breakdown strength and polarization are improved by Mn and Y co-doping. The optimal recoverable energy density of 9.75 J/cm3 for BYSTM is much larger than 3.54 J/cm3 for BST.

Enhanced electrostrain in Cu2+-doped Ba0.8Sr0.2TiO3

In this study we report large defect-mediated electrostrain (∼0.2%) in Cu2+-doped Ba0.8Sr0.2TiO3 (BST) ceramics. This electrostrain is due to the large reversible switching of the 90° domains facilitated by the defect dipoles. The increased tetragonality due to the J-T distortion in the Cu2+-doped compositions is also responsible for the higher electrostrains obtained. With the aid of Electron Paramagnetic Resonance (EPR) Spectroscopic studies, it is also found that, the nature of the defect dipoles significantly influences the electrostrain in these copper doped materials.

Structural and dielectric properties of B2O3/Li2O-added Ba0.6Sr0.4TiO3 multilayer ceramics for tunable devices

B2O3 and Li2O (B/L)-added Ba0.6Sr0.4TiO3 (BST) ceramics sintered at 940 °C exhibited a dense microstructure with large grains. The amount of B/L additive was 4.5 wt% with a B/L ratio of 1.5:1. The B/L-related liquid phase assisted the densification of the BST ceramics. This BST ceramic displayed a large dielectric constant (εr) of 2834 with a low dielectric loss (tan δ) of 0.21% at 1.0 MHz. It also displayed a large tunability (28.2% at 10 kV/cm) and a high figure of merit (FOM) of 134. BST thick-films were synthesized using the tape casting method. The thick-film densified at 940 °C exhibited a large tunability of 18.7% at 10.0 kV/cm and an FOM of 208; these are higher than the values reported in the literature. Multilayer ceramics (MLCs) consisting of five layers of 40-μm-thick BST thick-films and Ag electrodes were also fabricated at 940 °C. No diffusion occurred between the Ag electrode and BST thick-film. A large tunability of 67.6% at 52 kV/cm with a high FOM of 294 was obtained from this MLC. This verified that the B/L-added BST ceramic is effective for application in tunable multilayer devices.

Synthesis, characterisation and dielectric properties of low-loss Zr-doped barium strontium titanate materials

ABSTRACTA series of materials of the composition Ba0.7Sr0.3ZrxTi(1 − x)O3 (BSZT), where x = 0.00, 0.01, 0.02 and 0.03, were synthesised through the sol–gel method whereupon the manifestations of partial substitution of Ti4+ by Zr4+ on the structural and dielectric behaviour of Ba0.7Sr0.3TiO3 (BST) were studied. X-ray diffraction patterns of all samples showed the development of a single-phase crystalline perovskite structure. The dielectric behaviour of the ceramic samples has been studied in detail in the frequency range 10 Hz to 1 MHz at room temperature, and as a function of increase in temperature. The sample with 2% Zr recorded the highest dielectric constant. The dielectric loss values for all the BSZT compositions are remarkably low, tan δ = 0.021∼0.026 at 1 MHz, in contrast to the literature reports. It is observed that small amount of Zr doping on BST, where 0 < x ≤ 0.03 results in the enhancement of dielectric constant while decreasing the bulk density and dielectric loss.

Fabrication and Characterization of Fully Inkjet Printed Capacitors Based on Ceramic/Polymer Composite Dielectrics on Flexible Substrates

The preparation of fully inkjet printed capacitors containing ceramic/polymer composites as the dielectric material is presented. Therefore, ceramic/polymer composite inks were developed, which allow a fast one-step fabrication of the composite thick films. Ba0.6Sr0.4TiO3 (BST) is used as the ceramic component and poly(methyl methacrylate) (PMMA) as the polymer. The use of such composites allows printing on flexible substrates. Furthermore, it results in improved values for the permittivity compared to pure polymers. Three composite inks with varying ratio of BST to PMMA were used for the fabrication of composite thick films consisting of 33, 50 and 66 vol% BST, respectively. All inks lead to homogeneous structures with precise transitions between the different layers in the capacitors. Besides the microstructures of the printed thick films, the dielectric properties were characterized by impedance spectroscopy over a frequency range of 100 Hz to 200 kHz. In addition, the influence of a larger ceramic particle size was investigated, to raise permittivity. The printed capacitors exhibited dielectric constants of 20 up to 55 at 1 kHz. Finally, the experimental results were compared to different theoretical models and their suitability for the prediction of εcomposite was assessed.

All-Inorganic Flexible Ba0.67Sr0.33TiO3 Thin Films with Excellent Dielectric Properties over a Wide Range of Frequencies.

With rapid advances in flexible electronics and communication devices, flexible dielectric capacitors exhibiting high permittivity, low loss, and large electric-field tunability over a wide frequency range have attracted increasing attention. Here, a large-scale Ba0.67Sr0.33TiO3 (BST) dielectric thin film sandwiched between SrRuO3 (SRO) bottom electrode and Pt top electrode is fabricated on a flexible mica substrate. The mica/SRO/BST/Pt capacitor exhibits a dielectric constant (εr') of more than 1200, a loss tangent [tan(δ)] as low as 0.16, and a tunability of 67% at low frequencies around 10 kHz. Simultaneously, the capacitor can retain an εr' of 540 and a tan(δ) of 0.07 at microwave frequencies, e.g., 18.6 GHz. Moreover, even when the capacitor is bent to a small radius of 5 mm or undergoes 12 000 bending cycles (at 5 mm radius), almost no deterioration in εr', tan(δ), and tunability is observed. The excellent dielectricity and mechanical flexibility and durability endow the mica/SRO/BST/Pt capacitor with huge potential for flexible electronic and microwave applications.

Highly enhanced dielectric loss of MgO-doped Ba0.67Sr0.33TiO3 ceramics prepared by a non-contamination DCC-HVCI method

MgO-doped Ba0.67Sr0.33TiO3 (BST) ceramics with uniform microstructure and enhanced dielectric loss were prepared by direct coagulation casting via high valence counter ions (DCC-HVCI) method. MgO was utilized as acceptor dopant as well as coagulating agent to release Mg2+ solidifying ceramic suspensions. Effect of sintering temperature and MgO doping content on microstructure and dielectric properties of BST ceramics was investigated. It was found that the loss tangent value (tan δ) decreased remarkably from 0.025 to 0.004 with increasing MgO concentration from 0.5 to 1.5 mol%. The 1.5 mol% MgO-doped BST ceramics processed high density of 99.5% and tan δ of 0.004 which is improved by 150% compared with that of dry-pressed samples. This improvement can be attributed to the ubiquitous distribution of MgO in BST ceramic matrix leading to the enhanced inhibitive effect. This paper provides a novel facial route to prepare high-performance functional ceramics with high reliability and low cost.