Ba0.5Sr0.5TiO3 Research Articles

Control of the Surface Morphology of Ceramic/Polymer Composite Inks for Inkjet Printing

The use of organic/inorganic composite inks in the Drop on Demand inkjet printing technology is a promising as well as demanding approach for the fabrication of composite thick films. Therefore, a versatile ceramic/polymer composite ink system for inkjet printing is developed in this study, containing Ba0.6Sr0.4TiO3 (BST) and poly(methyl methacrylate) (PMMA). When developing such inks suitable for a one‐step fabrication, the major challenge is to fulfill the requirements of the inkjet printing technology and to obtain homogeneous surface morphologies after drying. Thus, possible influencing factors like the solvent composition, the solids content, and the ratio of ceramic to polymer are investigated to obtain a detailed knowledge for the general ink development. The fluid mechanical properties, viscosity, density, and surface tension are characterized. The main focus of this study lies on the drying behavior of the different inks, with the interactions of the ceramic particles, and the dissolved polymer molecules being highlighted. Furthermore, the drying behavior depending on the ink composition is shown. This study provides new insights into the possibility of using composite inks for the inkjet printing process and the fabrication of printed composite thick films in a single process step.

Microstructure and optical properties of Ba0.6Sr0.4TiO3 thin films prepared by pulsed laser deposition

Growth aspects of barium strontium titanate, Ba0.6Sr0.4TiO3 (BST) thin films grown on Si (100) and quartz substrates by pulsed laser deposition technique were investigated. The main objective of the work was to study the effect of substrate temperature and oxygen partial pressure on the microstructure and optical properties of the BST films. X-ray diffraction results revealed that the thin films were amorphous when the substrate temperature was up to 673 K and the crystallinity was found to be improved at the substrate temperature of 873 K. There was an increase in the lattice parameter value from 3.97 to 4.01 Å with an increase in the oxygen partial pressure. Scanning electron microscopy revealed smooth and uniform surfaces, while atomic force microscopy revealed that the particle size increased with decreasing oxygen partial pressure. UV-visible spectroscopy showed that the band gap of the BST films deposited on quartz substrate decreased from 4.41 to 3.73 eV as deposition temperature increased from 303 K to 873 K.

Influence of Y and Mn alternately doped order on the microstructures and dielectric properties of Ba0.6Sr0.4TiO3 films

ABSTRACTThe influences of Y and Mn alternately doped order on the microstructures and dielectric properties of the Ba0.6Sr0.4TiO3 (BST) films were reported in this paper. The Y and Mn alternately doped BST films were designed as YBST/MnBST/… and MnBST/YBST…multilayer films orderly expressed as (Y/Mn)M and (Mn/Y)M for short, and prepared on Pt/Ti/SiO2/Si wafers by an improved sol-gel method, where Y and Mn represent yttrium doped BST layer and manganese doped BST layer, and M is cycle unit, respectively. The microstructures of the alternately doped BST films were observed by SEM and the capacitance-voltage curves at 100 kHz or 1 MHz were measured by a HP4284A LCR meter and the dielectric properties in the range of 1GHz were measured by an E4991A impedance analyzer. Compared to Y or Mn doped multilayer BST film, (Y/Mn)M and (Mn/Y)M show higher dielectric tunability and lower dielectric loss with higher dielectric constant. Moreover, (Y/Mn)M show better dielectric properties than (Mn/Y)M because (Y/Mn)M show granular microstructures independent of M, while the (Mn/Y)M show granular microstructures when M is 2 and add to a surface layer of columnar microstructures on the granular microstructures when M is 4. The related mechanisms were obtained in terms of the XRD phase structures, the cross-sectional SEM microstructures and the AFM morphologies.

A reconfigurable miniaturized planar inverted‐F antenna with integrated BaSrTiO3 capacitor

AbstractIn this letter, a wide‐tuning range planar inverted‐F antenna (PIFA) of 17 × 10 mm2 dimension printed on a Rogers duroid RT5880 substrate is presented. The printed circuit board (PCB) dimensions are 1 × 60 mm2. First, the antenna is simulated with a localized capacitor and the effect of the capacitor losses on the antenna efficiency is studied. Then, the antenna is simulated with an integrated BaSrTiO3 (BST) tunable capacitor. The obtained results are in very good agreement with those obtained with localized elements. Finally, the BST thin film capacitor is fabricated and mounted on the antenna. The experimental results show a capacitor tunability of 56.7% at a bias voltage of 35 V, leading to an antenna agility of 42.2%.

Preparation and Characterization of Lead-Free (Ba<sub>0.4</sub>Sr<sub>0.4</sub>Ca<sub>0.2</sub>)(Zr<sub>0.05</sub>Ti<sub>0.95</sub>)O<sub>3</sub> Ceramics Using BST Seed Induced Method

The solid solution of lead-free (Ba0.4Sr0.4Ca0.2) (Zr0.05Ti0.95) O3 (BSCZT) ceramics were prepared from the seed induced method. The Ba0.6Sr0.4TiO3 (BST) were used as the seed crystals, they were prepared using the molten salt technique. The phase formation was examined using the X-ray diffraction technique (XRD). It was found that the single phase perovskite structure of BST was obtained at a temperature of 800°C. The ceramics were prepared using the conventional solid state reaction by adding of BST seed crystals at 2.5, 5, 7.5 and 10 mol%. The structure showed that a single phase perovskite was obtained after sintered at 1400 °C. This work confirmed that BST seed crystal successfully diffused into BSCZT ceramic and the BSCZT ceramic with a seed crystal showed higher dielectric than the BSCZT ceramic without seed crystals.

Highly dispersive Ba 0.6 Sr 0.4 TiO 3 nanoparticles modified P(VDF‐HFP)/PMMA composite films with improved energy storage density and efficiency

Polymer composite films with high energy density as well as high efficiency are promising dielectric materials in pulsed power systems. In improving the energy discharged efficiency, poly vinylidene fluoride-hexafluoropropylene [P(VDF-HFP)] film blended with 20 vol.% poly(methylmethacrylate) (PMMA), which has a much slimmer ferroelectric hysteresis loop, is employed as the polymer matrix. Highly dispersive Ba0.6 Sr0.4 TiO3 (BST) nanoparticles with an average particle size of 12.1 nm are utilised to improve the polarisation of the blend film without sacrificing the dielectric strength. Uniform nanocomposite films with high flexibility and excellent energy-storage performance are obtained. Especially, due to the optimisation of both polymer matrix and fillers, the BST modified P(VDF-HFP)/PMMA blend films show improved breakdown strength and depressed energy loss, which leads to an enhanced energy density of 10.3 J/cm3 at 378 kV/mm.

Flexoelectric effect in functionally graded materials: A numerical study

The flexoelectric effect has been observed in a wide range of dielectric materials. However, the flexoelectric effect can only be induced using the strain gradient. Researchers have examined the flexoelectricity using non-uniform loading (cantilever type) or non-uniform shape in dielectric materials, which may be undesirable in many applications. In the present article, we demonstrate induced flexoelectricity in dielectric functionally graded materials (FGMs) due to non-uniform Youngs’s modulus along the thickness. To examine flexoelectricity, Ba0.6 Sr0.4 TiO3 (BST) and polyvinylidene fluoride (PVDF) were used to numerically simulate the performance of FGMs. 2D simulation suggests that output voltage can drastically enhance for optimum grading index of FGMs.

High dielectric tunability in composites prepared using SiO2 coated Ba0.5Sr0.5TiO3 nanoparticles

Ba0.5Sr0.5TiO3 (BST) nanoparticles were coated with SiO2 using a chemical process. SiO2-coated BST was used as the starting material to prepare BST-xSiO2 (x = 0, 1.0, 2.0, 3.0, 4.0, and 5.0 wt%) composites via a conventional ceramic process. The influence of SiO2 on the structure and properties of these composites was systematically studied. Scanning electron microscopy (SEM) results showed that the porosity of the composites was obviously reduced by the addition of SiO2. X-ray diffraction (XRD) results indicated that, besides the perovskite phase of BST, a traceable secondary phase of BaTiSiO5 also existed. The formation of BaTiSiO5 was due to the reaction between SiO2 and barium from BST. This resulted in a lower phase transition temperature of BST phase in the composites. It was found that the dielectric constant and loss decreased with increasing SiO2 content. All the composites exhibited a low dielectric loss (< 0.01) and an almost frequency independent dielectric constant in a frequency range from 100 Hz to 100 kHz. All the composites exhibited a high tunability (> 47%). Although the tunability decreased with increasing SiO2 content, a higher tunability was achieved in the composites because the composites exhibited a much higher breakdown strength than the pure BST ceramics. Additionally, it was found that the tunability of the composites increased with the decrease of the operating temperature.

Dielectric and energy-storage performance of Ba0.5Sr0.5TiO3-SiO2 ceramic-glass composites

Ba0.5Sr0.5TiO3 (BST) nanoparticles coated with SiO2 were used as the starting material to prepare BST-xSiO2 (x = 0, 1.0, 2.0, 3.0, 4.0 and 5.0 wt%) ceramic-glass composites. The coated SiO2 results in the sintered composites with a lower porosity. All the composites exhibited an almost frequency independent dielectric constant that corresponds with a quite low dielectric loss (tanδ < 0.02) over a frequency range from 100 Hz to 1 MHz. It is found that the Curie temperature decreased with increasing x due to the reaction between the SiO2 and BST. As the x increased, the dielectric constant of the composites decreased and the electric breakdown strength increased. Interestingly, it is also found that the charge-discharge efficiency increased with an increasing x. The energy-storage density of more than 2.5 J/cm3 with a charge-discharge efficiency of about 80% was achieved in the composite with x = 1.0 wt%.

Filleted RDRA using novel ceramic dielectric (3G-BST) with stable gain and improved bandwidth for X-band application

In the present communication, a filleted rectangular dielectric resonator antenna (FRDRA) using novel synthesized ceramic dielectric is described. The proposed antenna has dual segment rectangular structure filleted at the edges of its upper surface. Teflon (εr = 2.1) occupies lower segment of the structure and liquid phase (3wt% of PbO-BaO-B2O3-SiO2 glass) sintered Ba0.5Sr0.5TiO3 (BST) namely 3G-BST (Average value of εr = 15) with filleted structure is used as upper segment. Liquid phase sintering reduces the manufacturing cost by reducing the sintering temperature of BST from 1250°C to 950°C without affecting the structure of ceramic with increasing density. The simulated impedance bandwidth of FRDRA is found to be 4.875GHz (7.735–12.610GHz), which is 8.57% greater than conventional dual segment rectangular dielectric resonator antenna (DS-RDRA). The experimental impedance bandwidth of FRDRA is 6.048GHz (7.0–13.048GHz). Among different feeding mechanisms, aperture-coupled feed mechanism is opted in the proposed antenna to reduce the spurious response and improve the antenna performance. Proposed FRDRA reduces material requirement and provides wider bandwidth with stable radiation pattern over its entire frequency band. The developed antenna is appropriate for use as primary feed in radar and satellite communication.

Residual stress effect on coupling electromechanical factor of epitaxial Barium Strontium Titanate (BST) thin films

Acoustoelastic (AE) effect of a mechanically pre-stressed layered piezoelectric structure of BST is investigated. Two samples of BST (Ba0.8Sr0.2TiO3) thin films were grown by rf-magnetron sputtering deposition techniques on a Pt(100)/MgO(100) and Pt(110)/MgO(110) substrates. The crystallographic orientation of BST thin films is analyzed by X-ray diffraction (XRD). A laser acoustic waves (LA-waves) technique is used to generate surface acoustic waves (SAW) propagating in both samples for epitaxial relationship examination. We perform an extended model to determine the residual stress and strain in BST films using the (XRD) X-ray diffraction measurement and the piezoelectric constitutive equations. Theoretical analysis of (SAW) propagation in a pre-stressed layered piezoelectric structure is achieved to discuss the effect of the measured residual stresses of BST films on the propagation behavior of Rayleigh waves and on the coupled electromechanical factor.

Enhanced energy storage properties of Ba0.4Sr0.6TiO3 lead-free ceramics with Bi2O3-B2O3-SiO2 glass addition

In this study, we present an effective strategy to enhance the energy storage properties of Ba0.4Sr0.6TiO3 (BST) lead-free ceramics by the addition of Bi2O3-B2O3-SiO2 (BBS) glass, which were prepared by the conventional solid state sintering method. The phase structure, microstructure and energy storage properties were investigated in detail. It can be found that the Ba0.4Sr0.6TiO3-x wt%(Bi2O3-B2O3-SiO2) (BST- x wt%BBS, 0≤x≤12) ceramics possess large maximum polarization (Pmax), low remanent polarization (Pr) and slim polarization electric field (P-E) hysteresis loops. The breakdown strength (BDS), recoverable energy storage density (Wrec) and energy storage efficiency (η) are enhanced obviously with the addition of BBS glass. The BST-9 wt%BBS ceramic is found to exhibit excellent energy storage properties with a Wrec of 1.98J/cm3 and a η of 90.57% at 279kV/cm. These results indicate that the BST-x wt%BBS ceramics might be good candidates for high energy storage applications.

Energy storage properties and electrocaloric effect of Ba0.65Sr0.35TiO3 ceramics near room temperature

Ba0.65Sr0.35TiO3 (BST) ceramics were synthesized by sol–gel route. The diffusion phase transition (DPT) characteristic was found in the temperature range from 150 to − 35 °C. The value of the DPT parameter γ values are 1.53 and 1.75, respectively at applied dc field of 0 and 16.7 kV/cm. It is implied that the phase transition of BST ceramics become more diffuse under the applied electric field. Temperature dependent polarization–electric field hysteresis loops were studied. It was found that the energy storage properties and electrocaloric effect near room temperature were the function of electric fields. The maximum value of recoverable energy density was 0.2812 J/cm3 with energy storage efficiency (η) of 78.67% obtained at room temperature under an electric field of 75 kV/cm. The largest η can achieve 98% under low electric field of 50 kV/cm. A large electrocaloric temperature change (ΔT max = 0.49 K) near room temperature was obtained by indirect method. Taken together, the ceramics have a promising candidate for energy-storage applications and cooling systems in the room temperature.

Experimental study of effect of strain on electrocaloric effect in (001)-epitaxial (Ba,Sr)TiO3 thin films

The effect of strain on the electrocaloric effect in (001)-epitaxial (Ba,Sr)TiO3 (BST) thin films was experimentally investigated via indirect estimation by measuring the electric field dependence of polarization at various temperatures. Compressively strained (Ba0.3Sr0.7)TiO3 films were deposited on (001)cSrRuO3/(001)SrTiO3 and (001)cSrRuO3/(001)(La0.3Sr0.7)(Al0.65Ta0.35)O3 (LSAT) by RF magnetron sputtering. The BST film on (001)cSrRuO3/(001)SrTiO3 showed a higher ferroelectric-to-paraelectric phase transition temperature than that on (001)cSrRuO3/(001)LSAT owing to the larger compressive strain. It was revealed that the electrocaloric effect is maximized at around the ferroelectric-to-paraelectric phase transition temperature modified by the compressive strain in the films.

High energy photon induced Fermi-level shift of Ba0.5Sr0.5TiO3 thin films

We have studied surface chemical states of Ba0.5Sr0.5TiO3 (BST) thin films as a function of high energy photon doses. BST thin films were deposited on Si substrates by Sputtering technique and post irradiations were carried out with high energy 60Co gamma radiation. Core-level and Fermi-level spectra were measured by X-ray photoelectron spectroscopy. The gamma-ray irradiated BST films showed a higher binding energy shift of Ba, Sr, and Ti core level with increasing gamma doses due to shift in Fermi level. The Fermi level is shifted towards conduction band by ~1.1eV for 200kGy gamma irradiated BST with respect to pristine. An increase in full width at half maximum of X-ray diffraction peak and surface roughness were also observed with increasing gamma doses. Higher leakage current and decrease in capacitance with gamma doses are further evidence of higher carrier concentration which is consistent with the shift in Fermi level.

Micro-structural, ferroelectric and magnetic properties of multiferroic composite system Ba0.5Sr0.5TiO3- Ni0.4Co0.2Zn0.4Fe2O4

ABSTRACTIn this paper, microstructural, ferroelectric and magnetic properties of multiferroic composite system (1-x) Ba0.5Sr0.5TiO3 (BST) – (x) Ni0.4Co0.2Zn0.4Fe2O4 (NCZF), where x = 0.1, 0.2, 0.3, 0.4 molar ratio have been studied. Grains of NCZF are larger in size and more symmetrical in comparison to BST grains. Overall grain size of BST grains in the composite samples decreases with increase in NCZF content. Polarization vs Electric Field (P-E) loops of the composite samples are unsaturated. The values of remanant polarization of the composite samples increase with increase in NCZF content. The composite samples possess saturated M-H loops with the values of remanant and saturation magnetization increases with increase in NCZF content.

Structural and dielectric properties of multiferroic composite system Ba0.5Sr0.5TiO3- Ni0.4Co0.2Zn0.4Fe2O4

ABSTRACTIn this paper, structural and dielectric properties of multiferroic composite system (1-x) Ba0.5Sr0.5TiO3 (BST) – (x) Ni0.4Co0.2Zn0.4Fe2O4 (NCZF) x = 0.1, 0.2, 0.3, 0.4 molar ratios have been studied. X-ray diffraction analysis of composite samples confirmed the presence of both the phases. Density measurements result indicate that composite samples although possess lower density in comparison to both the pure phases but density of the composite samples increases with NCZF content. Dielectric constant and loss of the composite samples decreases with increase in frequency due to Maxwell-Wagner relaxation mechanism. Dielectric constant of the composite samples firstly increases with increase in NCZF content followed by a decrease.

Oxygen influence in the magnetic and the transport properties of ferroelectric/ferromagnetic heterostructures

Oxygen vacancies in oxides nanostructures are the origin of many intriguing phenomena. We have studied the influence of the oxygen pressure in the tunneling properties of a ferroelectric barrier, Ba0.25Sr0.75TiO3 (BSTO), grown over a ferromagnetic electrode. A phenomenological model description was used to obtain critical information about the structure and electrical properties of ultra-thin BSTO layers using conductive atomic force microscopy. The BSTO layers present good insulation properties. Reducing the oxygen content increases the conductivity of the samples. The tunneling of the current carriers is probably the main conduction mechanism for samples with higher barrier thicknesses.

Synthesis of Ba0.6Sr0.4TiO3 platelet crystals based on Bi4Ti3O12 precursor by topochemical microcrystal conversion

A-site complex perovskite Ba0.6Sr0.4TiO3 (BST) platelet microcrystals were successfully synthesized using a two-step Molten Salt Synthesis (MSS) method based on Bi4Ti3O12 platelet precursor. During the synthesis process, the calcination temperature and the soaking time strongly influence on the morphology and particle size of BST. The optimal temperature for calcination is 740 °C. In addition, the increasing edge length with 5 μm–11.5 μm and thickness with less than 0.25 μm of BST platelets are obtained under the condition of rising soaking time from 5 h to 20 h, which can be used for preparing highly textured ceramics and microwave devices. Finally, the mechanism of topochemical microcrystal conversion reaction between BaCO3-SrCO3 mixture and Bi4Ti3O12 was discussed.

Enhanced structural, dielectric, ferroelectric, and piezoelectric properties of (1−x)Ba0.9Sr0.1TiO3–(x)Ba0.7Ca0.3TiO3 ceramics derived using mechano‐chemical activation technique

AbstractThe effect of Ba0.7Ca0.3TiO3 (BCT) substitution on the structural, dielectric, ferroelectric, and piezoelectric properties of mechano‐chemically synthesized lead‐free (1−x)Ba0.9Sr0.1TiO3‐(x)Ba0.7Ca0.3TiO3 (x=0.0, 0.10, 0.20, 0.35, and 0.50) ceramics have been investigated. XRD patterns confirms the formation of tetragonal phase with P4mm space group. The results indicate a strong influence of BCT substitution on the structural and electrical properties of Ba0.9Sr0.1TiO3 (BST) ceramic. BST–BCT ceramic for x=0.35 have shown high dielectric constant εm~21 800, high remnant polarization Pr~10.16 μC/cm2, large piezoelectric charge constant D33~293 pC/N, large piezoelectric voltage constant g33~5.80 mV·m/N, and highest dielectric breakdown strength Ebd~224 kV/cm among the five synthesized samples. The correlation between structural, dielectric, ferroelectric, and piezoelectric properties of the BST ceramic with increasing BCT content have been systematically described on the basis of domain wall motion and grain size effect.