Barium Strontium Titanate Nanoparticles Research Articles

The Role of Silanization of Barium Strontium Titanate Nanopowders on the Dielectric Constant and Thermal Stability of Epoxy Nanocomposites

AbstractThis paper reports polymer composites′ microstructure and dielectric properties based on an epoxy resin matrix containing different amounts (from 2–10 wt. %) of barium strontium titanate nanoparticles. (Ba,Sr)TiO3 was prepared using the hydrothermal method, showing an average particle size of 100 nm. The composites′ thermal properties and morphology were characterized using thermogravimetric analysis, differential scanning calorimetry, and scanning electron microscopy. Our studies show that the (Ba,Sr)TiO3 nanoparticles were well dispersed in the epoxy resin matrix thanks to controlled silane functionalization. Accordingly, the glass transition temperature (Tg) value of the nanocomposites was found to be 159.0 °C at 10 wt. % (Ba,Sr)TiO3 loading and is higher than the neat epoxy resin Tg (Tg=154.7 °C). Moreover, the dielectric composite properties were investigated comprehensively via a wide range of frequencies from 10 Hz to 100 kHz. The results indicate that (Ba,Sr)TiO3 nanopowders and the surface modifying filler play a crucial role in the significant increase of the dielectric constants, approximately 1.5 times at the optimum added amount (Ba,Sr)TiO3. The limited functionalization of (Ba,Sr)TiO3 nanoparticles by the silane affords to control the nanocomposite dielectric loss. Furthermore, the nanocomposites also exhibited good thermal stability.

Tuning Ba/Sr ratios of BaxSr1-xTiO3 of polymer nanocomposites toward significant enhancement of energy storage performance by optimized phase composition

The rapid development of portable electronic equipment, hybrid electric vehicles and pulse power systems have put forward higher requirements for new dielectric materials, making flexible polymer dielectrics attractive. Barium strontium titanate nanoparticles with different compositions were successfully prepared by using oxalate. A series of PVDF/BaxSr1-xTiO3 nanoparticles nanocomposites were prepared using the semi-crystalline ferroelectric polymer polyvinylidene fluoride PVDF as the polymer matrix. The microstructure and electrical properties of the nanocomposites were characterized to explore the effects of the composition and intrinsic properties of the filling phase on the nanocomposites. Among all the groups of nanocomposites, the 1 vol% PVDF/Ba0.6Sr0.4TiO3@DA NPs has the highest discharge energy density at the breakdown field strength, which is 7.8 J/cm3. The excellent discharge energy efficiency of 1 vol% PVDF/Ba0.6Sr0.4TiO3@DA NPs is maintained at 65 % at 300 kV/mm. This paper can provide experimental guidance and theoretical basis for the development of high energy storage density dielectric materials and their application in dielectric energy storage capacitors.

Characteristic Making of Ba0.4Sr0.6TiO3 Thin Film Nanoparticles

Presently, the research on thin films is essentially useful in the world of science and technology. Therefore, this study aims to explore Barium Strontium Titanate (BST) as the basis in the making of dynamic random access memory (DRAM). This DRAM technology produces small cells that have faster operations, lower energy, longer data storage period, and are found to havemade up of Barium Strontium Titanate nanoparticles (Ba0.4Sr0.6TiO3; BST). BST applications in the form of capacitors can be used as gas sensors, temperature sensors, microwave phase shifters, tunable filters, oscillators, infrared sensors, etc.The main component of BST was showed by the sol-gel method, and the device structure constituted of Si/SiO2/RuO2/TiO2 /Ba0.4Sr0.6TiO3/Al. All the samples were annealed at 400, 450, 500, 550, 600, 650 and 700 ℃ for 60 min. The sample was annealed to see the crystalline structure of the sample.The sol gel method was chosen in the process of making thin films of Ba0.4Sr0.6TiO3 (BST) because this method was easier and cheaper than other techniques. The thin film was characterized by optical and electrical properties. The results showed that a rise in the annealing temperature increased the crystalline, grain size, thickness and surface roughness of the sample. The characterization was carried out on the device structure (Si/SiO2/RuO2/TiO2/Ba0.4Sr0.6TiO3/Al) in order to examine the optical and electrical properties, including the current density and the dielectric features. At the annealing temperature of 700 ℃, the device showed the best value, with the absorption peak at the wavelength of 688 nm. And also, with the dielectric constant (εr) of 2,500, capacitance (C) of 22.10 nF, dense alternating current (ρau) of 2.54×104 Ω.m, conductance (σau) of 1.20×10-2 1/Ω.m, and current density of 9.85×10 -5 A.cm-2 at 0.5 V. The results of characterization of this capacitor are very good to be used as an infrared sensor.
 HIGHLIGHTS
 
 The explore Barium Strontium Titanate (BST) as the basis in the making of dynamic random access memory (DRAM)
 BST applications in the form of capacitors can be used as gas sensors, temperature sensors, microwave phase shifters, tunable filters, oscillators, infrared sensors, etc.
 The results showed that a rise in the annealing temperature increased the crystalline, grain size, thickness and surface roughness of the sample
 
 GRAPHICAL ABSTRACT

Compact Wideband Circularly Polarized Dielectric Resonator Antenna With Dielectric Vias

Using dielectric vias, we propose a compact and wideband circularly polarized (CP) dielectric resonator antenna (DRA). The dielectric vias are realized by filling barium strontium titanate nanoparticles with a dielectric constant of 20 into a perforated printed circuit board (PCB) substrate. Owing to the high effectivedielectric constant of the dielectric via-loaded PCB substrate, the electrical size of the DRA is reduced. The arrangement of dielectric and air vias inside the DRA structure allows for redistributing the resonant frequencies of different radiating modes. This design incorporates a third higher-order mode into the passband, resulting in wide impedance and axial ratio (AR) bandwidths. A cross slot is used to excite the CP fields. The standard PCB process is utilized to manufacture the antenna structure. The fabricated prototype has measured impedance and AR bandwidths of 46.9% and 26.7%, respectively. The measured overlapping bandwidth is 25.4%. Our prototype has a compact footprint of 0.61 × 0.61 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\lambda^2_0$</tex-math></inline-formula> where λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> is the wavelength in free space at the center frequency. The proposed dielectric vias technique has potential abilities in size reduction and bandwidth enhancement.

Design of Substrate-Integrated Dielectric Resonator Antenna With Dielectric Vias

For the first time, dielectric vias were used to design a substrate-integrated dielectric resonator antenna (SIDRA). The dielectric vias consist of cylindrical holes drilled into the PCB substrate and filled with presintered nanoparticles of barium strontium titanate (BST). The BST nanoparticles were found to have a dielectric constant of 20, with an approximate loss tangent of ~0.05. The dielectric-vias loaded substrate constitutes an effective medium for the DRA design. The dielectric vias are arranged in a concentric manner around a core substrate material region, giving a wideband multiring SIDRA. It was found that the wideband behavior is due to two different dielectric resonator modes, namely, the TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">δ11</sub> mode and TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">δ31</sub> half-mode. The TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">δ31</sub> half-mode is a modified version of the TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">δ31</sub> -mode of a regular dielectric resonator and is reported here for the first time. The measured and simulated -10-dB impedance bandwidths of the DRA are 33.4% and 35.8%, respectively.

Structural, optical and electrical studies on zinc doped barium strontium titanate as photo-anode for DSSC device

Nano crystalline Barium strontium titanate (BST) and zinc doped barium strontium titanate (BSZT) with general formula Ba0.5−xSr0.5ZnxTiO3 (x = 0, 0.05, 0.10 and 0.15) were synthesized by modified sol–gel method. The synthesized nano crystalline powders were characterized using XRD, UV-DRS, FTIR, FESEM, particle size analysis (PSA) and I-V Photovoltaic tests. The structural, optical and electrical properties of the nano crystalline powders were explored. XRD results confirm the formation of cubic structure and their average crystallite size is estimated. The electrical investigation indicates that the addition of Zn to BST nanoparticles improves the conductivity of the sample, hence it could be potential candidate for the solar cells.

PVDF/PMMA dielectric films with notably decreased dielectric loss and enhanced high‐temperature tolerance

ABSTRACTPolymer dielectrics generally have comparatively low dielectric constant, operating temperatures, and/or high dielectric loss, which limits their uses especially in harsh environment. In this article, a novel trilayered nanocomposite film (TNF) was constructed via solution‐casting and, subsequently, hot‐pressing process, which was composed of two outer layers of polyvinylidene fluoride (PVDF, high dielectric constant) and a middle layer of polymethyl methacrylate (PMMA, high glass transition temperature, Tg). The two outer layers of TNF were filled with barium strontium titanate nanoparticles to further increase the dielectric constant of PVDF. The PMMA in the middle layer was used to largely suppress the dielectric loss and simultaneously improve the temperature tolerance of TNF. Results show that the introduction of PMMA induced oriented crystal formation in the interface regions between PVDF and PMMA components. Moreover, most of the impurity ions were dramatically immobilized by partly oriented α crystals and high Tg PMMA layer until the temperature exceeded 120 °C. Therefore, the TNFs showed a high‐temperature tolerance and notably decreased loss, which are promising for widespread energy storage applications where harsh working conditions are present. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019, 57, 1043–1052

Strong tribocatalytic dye decomposition through utilizing triboelectric energy of barium strontium titanate nanoparticles

In the suspensions with the Ba0.75Sr0.25TiO3 (BST) nanoparticles with an average size ~20 nm for triboelectric energy harvesting, dye decompositions were found to occur readily in the course of a normal stirring in dark at room temperature. More importantly, the decomposition efficiency can be greatly improved through some simple modifications in stirring rods and as high as 99.0% Rhodamine B can be decomposed in 3 h under a mild stirring of 300 rpm. Some well-designed experiments have been conducted, which show that the observed dye decompositions are directly related to the friction between BST nanoparticles and stirring rods in magnetic stirring. It is proposed that with the mechanical energy absorbed from friction, the BST nanoparticles have exerted a novel tribocatalytic effect for dye decompositions, which is confirmed by the detection of intermediate products of •OH and •O2− in stirring. These results clearly demonstrate that nanostructured oxides have the capability to harvest mechanical energy from ambient environment through friction for dye decomposition, which represents an important application for harvesting mechanical friction energy.

Enhanced properties of SPEEK with incorporating of PFSA and barium strontium titanate nanoparticles for application in DMFCs

Novel blend nanocomposite proton-exchange membranes were prepared using sulfonated poly (ether ether ketone) (SPEEK), perfluorosulfonic acid (PFSA), and Ba0.9Sr0.1TiO3 (BST) doped-perovskite nanoparticles. The membranes were evaluated by attenuated total reflection, X-ray diffraction spectroscopy, water uptake, proton conductivity, methanol permeability, and direct methanol fuel cell test. The effect of two additives, PFSA and BST, were investigated. Results indicated that both proton conductivity and methanol barrier of the blend nanocomposite membranes improved compared with pristine SPEEK and the as-prepared blend membranes. The methanol permeability and the proton conductivity of the blend membrane containing 6 wt% BST obtained 3.56 × 10−7 cm2 s−1 (at 25 °C) and 0.110 S cm−1 (at 80 °C), respectively. The power density value for the optimum blend nanocomposite membrane (15 wt% PFSA and 6 wt% BST) (54.89 mW cm-2) was higher than that of pristine SPEEK (31.34 mW cm-2) and SPF15 blend membrane (36.12 mW cm-2).

High energy density polymer nanocomposites with Y‐doped barium strontium titanate nanoparticles as fillers

Dielectric nanocomposites with an enhanced energy density are highly desired in modern electronic and electrical power systems. In this study, the authors developed a new flexible dielectric nanocomposite thin film using Y-doped barium strontium titanate (Y:BST) nanoparticles as fillers and polyvinylidene fluoride as a polymer matrix. The nanocomposites exhibited a high energy density of 11.07 J/cm3 at 4300 kV/cm with a low filler content. Through the analysis of defect chemistry with X-ray photoelectron spectroscopy, the dopant Y3+ occupies A-site of the perovskite structure, which is associated with the generation of Ba&Sr vacancies and oxygen vacancies for charge compensation. As a result, TiO6 2– octahedron distortion occurs, which is responsible for the enhanced dielectric permittivity. Meanwhile, the dielectric loss maintains a low level and the breakdown strength increases at a low filler loading, resulting in improved energy density.

A Modularized and Switchable Component for Flexible Passive Device: Terahertz Photonic Crystals with Fine‐Tuning

AbstractIn this work, tunable terahertz photonic crystals (PCs) used as modularized and switchable components in flexible passive device are designed and prepared. Flexible woodpile structures created by the direct‐writing technology with a composite ink system composed of barium strontium titanate nanoparticles and polydimethylsiloxane are immersed in 5CB liquid crystals (LCs), where the orientation of LC molecule is modulated by the external magnetic field. Each of these can work in terahertz wavelength with specific position and depth of the dips in the transmittance spectra due to different geometries as well as having the ability of fine‐tuning. Experiments show that the photonic gaps of these PCs can cover from 0.2 to 0.3 THz, as well as about 7.5% fine tunability of photonic gap appearing with the orientation change of the magnetic field. More interestingly, the dips of photonic gaps keep the same position but become deeper with the increase of layer, an ability to realize another dimensional switchover. This work demonstrates that efficient terahertz PCs with different geometry parameters could be dynamically tuned by the orientation of magnetic field and it can open a universal approach to shrinking the size of device and rapid manufacturing in a large throughput.

All-Printed Flexible Microwave Varactors and Phase Shifters Based on a Tunable BST/Polymer

This paper presents all-printed varactors and phase shifters using direct-ink writing methodologies on flexible organic films. The key enabler is a novel ferroelectric nanoink that allows printing high dielectric constant, low loss, and electrostatically tunable dielectrics at extremely low temperatures. The dielectric is made by suspending nanoparticles of barium strontium titanate (BST) in thermoplastic cyclic olefin copolymer (COC) to create a multiphase BST/COC nanocomposite. Unlike conventional ferroelectric ceramics, this ferroelectric dielectric requires no sintering and can be printed on any substrate. After printing, it is cured at temperatures below 200 °C. Careful stoichiometry and particle analysis of BST powders resulted in identifying conditions for achieving electrostatic tunability. A high relative permittivity of ${ \varepsilon _\text{r} = 38}$ and a very low dielectric loss of ${\tan \delta = 0.002}$ at $f= 10$ GHz were measured for the printed sinterless dielectric. The ink allows printing voltage-variable capacitors with a capacitance tunability up to 10% at microwave frequencies. The tunable capacitors were utilized in a left-handed transmission line design to create all-printed tunable phase shifters with up to a maximum phase shift of $\Delta \phi = {97}$ ° and a maximum figure of merit of 29°/dB at $f= 10$ GHz.

Characterization of microwave-sintered barium strontium titanate nanoparticles prepared by the hydrothermal method

The hydrothermal technique was used to synthesize barium strontium titanate nanoparticles of Ba1−xSrxTiO3 (BSTx), where x = 0.2 and 0.3. The nanoparticles of BSTx are annealed at 800 °C for 1 h to stabilize the crystalline phase. The annealed BSTx was used to produce ceramic bodies employing a microwave sintering at 1200 °C. Effectively, BSTx samples are synthesized via double-sintering route. BST0.20 and BST0.30 are subjected to the particle size analysis, crystal structure analysis and dielectric and ferroelectric properties. The observations are interesting and the results could be correlated and compared with earlier reports.

Anticipatory life-cycle assessment of supercritical fluid synthesis of barium strontium titanate nanoparticles

The life-cycle impacts of the supercritical fluid synthesis production of barium strontium titanate nanoparticles were assessed at the lab-scale and compared to conventional synthesis methods.

Abnormal cubic-tetragonal phase transition of barium strontium titanate nanoparticles studied by in situ Raman spectroscopy and transmission electron microscopy heating experiments

Phase stability of the ferroelectric materials at high temperature is extremely important to their device performance. BaxSr1−xTiO3 (BST) nanoparticles with different Sr contents (x = 1, 0.91, 0.65, 0.4, and 0) are prepared by a facile hydrothermal method. Using Raman spectroscopy and transmission electron microscopy (TEM) analyses under in situ heating conditions (up to 300 °C), the phase transitions of BST nanoparticles between 25 °C and 280 °C are comprehensively investigated. The original Curie temperature of BST nanoparticles decreases abruptly with the increase in Sr content, which is more obvious than in the bulk or film material. Besides, an abnormal phase transition from cubic to tetragonal structure is observed from BST nanoparticles and the transition temperature rises along with the increase in Sr content. Direct TEM evidences including a slight lattice distortion have been provided. Differently, BaTiO3 nanoparticles remained in the tetragonal phase during the above temperature ranges.

The enhanced electrocaloric effect in P(VDF-TrFE) copolymer with barium strontium titanate nano-fillers synthesized via an effective hydrothermal method

An effective hydrothermal method is developed to synthesize barium strontium titanate nanoparticles with a mean size below 30 nm, which are used for the fabrication of nanocomposite films consisting of P(VDF-TrFE) and ceramic nanoparticles.

A Solution Processed Flexible Nanocomposite Electrode with Efficient Light Extraction for Organic Light Emitting Diodes

Highly efficient organic light emitting diodes (OLEDs) based on multiple layers of vapor evaporated small molecules, indium tin oxide transparent electrode, and glass substrate have been extensively investigated and are being commercialized. The light extraction from the exciton radiative decay is limited to less than 30% due to plasmonic quenching on the metallic cathode and the waveguide in the multi-layer sandwich structure. Here we report a flexible nanocomposite electrode comprising single-walled carbon nanotubes and silver nanowires stacked and embedded in the surface of a polymer substrate. Nanoparticles of barium strontium titanate are dispersed within the substrate to enhance light extraction efficiency. Green polymer OLED (PLEDs) fabricated on the nanocomposite electrode exhibit a maximum current efficiency of 118 cd/A at 10,000 cd/m2 with the calculated external quantum efficiency being 38.9%. The efficiencies of white PLEDs are 46.7 cd/A and 30.5%, respectively. The devices can be bent to 3 mm radius repeatedly without significant loss of electroluminescent performance. The nanocomposite electrode could pave the way to high-efficiency flexible OLEDs with simplified device structure and low fabrication cost.

Fabrication and Thermal Properties of Polyimide/Ba0.77Sr0.23TiO3 Nanocomposites

Polyimides (PIs) are considered to be one of the most important engineering materials. The nano-particle of barium strontium titanate (BST) with formulation of Ba0.77Sr0.23TiO3 was synthesized by the sol-gel method. In this process, different contents of BST suspensions in polyamic acid (PAA) solution were imidized by heat treatment to form PI/BST nanocomposites. Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), simultaneous thermal analysis (STA), scanning electron microscope (SEM), and transmission electron microscopy (TEM) were used to characterize the structure and properties of the obtained nanocomposites. It was found that the BST nanoparticles sized 32–40 nm were dispersed homogeneously in the polyimide matrix without aggregation. The ζ potential of PI/BST 33 vol.% was decreased in contrast with that of the pure polyimide. The coefficient of thermal expansion (CTE) of PI/BST 33 vol.% was measured between 36°C and 600°C. CTEs comparison showed about 80% decrease in the CTE value of the nanocomposite in respect to the pure polyimide in a wider temperature range.

Electrical energy density and dielectric properties of poly(vinylidene fluoride-chlorotrifluoroethylene)/BaSrTiO 3 nanocomposites

A series of poly(vinylidene fluoride-chlorotrifluoroethylene) (P(VDF-CTFE))/barium strontium titanate (BST) nanocomposites were fabricated by solution casting method. The addition of BST nanoparticles could enhance both the dielectric constant and the displacement of the resultant composite significantly. The surface activation of BST nonaparticles with KH550 was confirmed as an effective way to improve the breakdown strength of the composite. The high electric displacement ( D > 15 μC/cm 2), breakdown field (>200 MV/m) and low dielectric loss in P(VDF-CTFE)/BST nanocomposites suggest that the high electrical energy density may be desirable. That indicates the potential application of this class of copolymer/ceramics nanocomposites for high energy storage components.

Fabrication of highly dispersed crystallized nanoparticles of barium strontium titanate in the presence of N,N-dimethylacetamide

Highly dispersed nanoparticles of barium strontium titanate (BST) were successfully synthesized by hydrolysis method using N,N-dimethylacetamide as a solvent at 120 °C and 140 °C. X-ray diffraction analysis (XRD) showed that the as-prepared particles presented a perovskite polycrystalline structure. The result of transmission electron microscopy (TEM) images revealed the particle size in the range of 5–30 nm. The composition without any annealing treatment characterized with the parallel plate capacitor method displayed good dielectric properties.