TiO3 Nanoparticles Research Articles

Sol-gel synthesized and microwave heated Pb0.8-yLayCo0.2TiO3 (y = 0.2–0.8) nanoparticles: Structural, morphological and dielectric properties

In this work, the Pb0.8-yLayCo0.2TiO3 (y = 0.2–0.8) (PLCT) nanoparticles were prepared by sol-gel method and further subjected to microwave heating. The formed tetragonal reflection planes of PLCT samples were on par with PbTiO3 (PT) and lanthanum cobalt titanate (LCT) tetragonal phases. Especially, for y = 0.2–0.4, PLCT attained the PT structure while for y = 0.6–0.8, PLCT acquired the LCT structure. That is, the structural transformation occurred from tetragonal PT to tetragonal LCT phases at higher La-contents. The high resolution transmission electron microscope (HRTEM) and field emission scanning electron microscopes (FESEM) showed complete formation of nanofibers at y = 0.8 which may reveal drug delivery system applications. The Fourier transform infrared spectra (FTIR) were recorded in order to find the presence of metal oxide bonds. The dielectric properties evidenced that the transition temperatures (Tc) were found to be increasing from 713 to 783 K with increase of y-value. Furthermore, the temperature and frequency dependence of dielectric constant (ε′), dielectric loss (ε′′), ac-electrical conductivity (σac), real (M′) and imaginary (M′′) parts of complex dielectric modulus (M*) was described. The Power law was used to fit the logσac versus logω plots in order to determine the dc-conductivity (σdc) and exponent (n) values of the samples at room temperature (RT). Later on, the Arrhenius plots (lnσac versus T−1 plots) were drawn to find the activation energies. The results expressed the existence of two activation energies at low and high temperature regions due to slope change before and after Tc.

Structural stability, enhanced magnetic, piezoelectric, and transport properties in (1-x)BiFeO3–(x)Ba0.70Sr0.30TiO3 nanoparticles

Multiferroic samples with composition (1-x)BiFeO3-(x)(Ba0.70Sr0.30)TiO3 (BFO-BST) were synthesized using a sol-gel route to study the effect of BST doping on structural, transport, and magnetic properties in BiFeO3 (BFO). X-ray diffraction studies with Rietveld analysis revealed that a phase transition occurred from rhombohedral (R3c) (0.0 ≤ × ≤ 0.15) to tetragonal (P4 mm) for x = 0.20 and nanocrystalline nature confirmed by transmission electron microscopy measurements. Piezoelectric properties improved as x increased from x = 0.0 (58 pC/N) to x = 0.20 (112 pC/N) increasing distortion in the crystal structure as evinced by Williamson-Hall analysis. Ferromagnetism was observed in doped BFO, different from the antiferromagnetic ordering in bulk BFO, indicating the noteworthy size effects and Fe-O-Fe bond angle variations in the magnetic ordering of BFO. An improvement in ferroelectric properties is observed with doping of BST compared to pristine BFO. Thermally activated conduction behavior occurred at low and high temperature regions as revealed by temperature dependent dc resistivity measurement. Effective improvements in dielectric response, meaning high dielectric constant with a low dielectric loss, were found in the doped samples.

Effect of the Molar Concentration of a Solution on Nanocomposite Crystal Growth in Ferroelectric-Carbon Nanotube Composites Fabricated by using the Sol-gel Method

In this study, Pb(Zr,Ti)O3 (PZT) nanoparticles directly were successfully grown on carbon nanotubes by mixing a PZT solution prepared by using the sol-gel method with functionalized carbon nanotubes. During this process, the effects of the concentration of the PZT solution on the size, crystallinity, and composition ratio of the PZT nanoparticles on the carbon nanotubes were investigated. As the molar concentration of the PZT solution was increased from 0.05 M to 0.2 M, the particle size increased from 6.628 nm to 10.877 nm. As the size of the nanoparticles increased, the surface directions became more diverse. In terms of the crystal structure, the tetragonality of PZT increased with increasing molarity of the PZT solution. This improvement in crystallinity can be further linked to an increase in the ferroelectricity of the PZT-carbon nanotubes, so the nanocomposite fabrication method using carbon nanotubes is expected to affect the characteristics of ferroelectric materials and can be used to further improve the properties of those.

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.

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%.

Zinc modified cadmium titanite nanoparticles: Electrical and room temperature methanol sensing properties

In this work ZnxCd1−xTiO3 (x=0.25, 0.5, 0.75) nanoparticles were synthesized using solid state reaction method. Detailed investigation of electrical properties and room temperature methanol sensing characteristics of synthesized nanoparticles was carried out. X-ray diffraction (XRD) and Scanning Electron Microcopy (SEM) were used to determine the crystal structure and morphology of the prepared material. The transition from positive temperature coefficient of resistivity (PTCR) to negative temperature coefficient of resistivity (NTCR) was observed in Zn0.75Cd0.25TiO3, Zn0.50Cd0.50TiO3 and Zn0.25Cd0.75TiO3 nanoparticles at 268K, 248K and 278K respectively. Prototype sensors of prepared ZnxCd1−xTiO3 (x=0.25, 0.5, 0.75) nanoparticles were tested at 10ppm, 20ppm, 30ppm and 40ppm of methanol at room temperature. The Zn0.75Cd0.25TiO3 and Zn0.25Cd0.75TiO3 nanoparticles sensors exhibited fast response and recovery times and a linear response with increase in methanol concentration. The Zn0.5Cd0.5TiO3 nanoparticles sensors exhibited nonlinear response and slow response and recovery times. Response of sensors based on all compositions was stable over period of 30 days.

Enhanced the breakdown strength and energy density in flexible composite films via optimizing electric field distribution

High energy density flexible composite films have been used for the modern compact electronic devices and electric power systems. A novel nanocomposite film is developed by embedding polydopamine encapsulated Ba0.6Sr0.4TiO3 nanoparticles (BST NPs) in the polyvinylidene fluoride polymer matrix. The surface functionalization of BST NPs with polydopamine facilitates favorable interaction between the particle and polymer phase, enhancing nanoparticle dispersion. The elaborate functionalization of BST NPs with polydopamine has guaranteed both the increase of dielectric constant and the maintenance of breakdown strength, resulting in significantly enhanced energy storage capability. A finite element simulation of electric field and electric current density distribution suggested the functionalized BST NPs significantly enhanced the breakdown strength and energy density of the composite films. The nanocomposite with 2.5 vol% functionalized BST NPs displays a high energy density of 6.3 J cm−3 at the low field of 3500 kV m−1, which is larger than that of the biaxially oriented polypropylenes (BOPP) (1.2 J cm−3 at the field of 6400 kV m−1). Therefore, the proposed flexible composites films would also find their potential application prospects in electrical devices such as mobile electronic devices, hybrid electric vehicles and military.

Preparation and dielectric properties of polyimide/Ba0.7Sr0.3TiO3 nanocomposite film

Ba0.7Sr0.3TiO3 (BST) nanoparticles were incorporated into polyimide (PI) matrix to obtain the nanocomposite films via solution casting method. The prepared BST/PI nanocomposite films were thoroughly characterized. X-ray diffraction measurements revealed that these films were amorphous in nature.They exhibited high thermal stability up to 519°C in nitrogen atmosphere with 5% weight loss, and high glass transition temperature up to 311°C. The nanocomposite films exhibited good mechanical properties. Dielectric constant of the film increases from 3.23 to 11.8 at 1 Hz frequency, as the BST content increases from 0 to 5 wt%, which is mainly due to the high dielectric constant of BST.

Fabrication of lead-free Ba(Zr0.2Ti0.8)O3–(Ba0.7Ca0.3)TiO3 nanoparticles and the application in flexible piezoelectric nanogenerator

Recently, flexible nanogenerators have attracted much attention due to the continuous demand of portable electronic devices. Thus, in our present work, a flexible piezoelectric nanogenerator (pNG) was fabricated by mixing 0.5Ba(Zr0.2Ti0.8)O3-0.5(Ba0.7Ca0.3)TiO3 nanoparticles (BCTZ NPs) and a PDMS polymer matrix. The flexible device exhibited excellent performance with maximum open-circuit voltage of 0.6V and short-circuit current of 7.5nA. BCTZ NPs were prepared by a reaction between a metallic salt and a metallic oxide in a solution of composite-hydroxide eutectic. XRD pattern showed BCTZ NPs to have pure perovskite structure. In this paper, the structure, morphology of the BCTZ NPs, and electric property of the BCTZ-based pNG were systematically studied. With the advantages of small-size, environmentally friendly, high flexibility, and high-sensitivity to external vibration, BCTZ will open up a range of new applications.

A surfactant-free route to synthesize Ba x Sr1−x TiO3 nanoparticles at room temperature, their dielectric and microwave absorption properties

Perovskite materials, such as Ba x Sr1− x TiO3 (BST), have been continuously receiving attentions due to their unique ferroelectric, pyroelectric, dielectric, piezoelectric and electric-optic properties. Here, we report a facile route for the synthesis of BST nanocrystalline materials by fast mixing of MCl2 (M = Ba, Sr) aqueous solution and titanium isopropoxide ethanol solution at room temperature without using any surfactants or structure-directing templates. The molar ratio of Ba/Sr was controlled by adjusting the original molar ratio of BaCl2·2H2O and SrCl2·6H2O. The dielectric properties and microwave absorption capability of the BST nanocrystalline were studied. The results indicate that the BST nanocrystalline material has the best dielectric and microwave absorption properties in the case of Ba0.7Sr0.3TiO3. The present strategy is facile, low cost and high yield, which may provide a new route for the synthesis of other perovskite materials.

Enhancement of lithium conductivity and evidence of lithium dissociation for LLTO-PMMA nanocomposite electrolyte

We report the effect of La0.57Li0.3TiO3 (LLTO) nanoparticles addition, with different crystallite size, on the lithium conductivity of LLTO-PMMA nanocomposites. X-ray powder diffraction and differential scanning calorimetry analyses showed a moderate increase of the disorder on the polymer chains with the addition of LLTO nanoparticles. Confocal Raman spectroscopy analysis evidenced lithium nitrate dissociation for both LLTO-loaded and unloaded polymer. Additionally, this technique also revealed that the free nitrate anions are mostly located in the proximity of LLTO nanoparticles interface, thus evidencing its participation in the lithium dissociation on these nanocomposites. An enhancement in the lithium conductivity in more than one order of magnitude was observed for all nanocomposites, in respect to LLTO-unloaded polymer, showing a maximum lithium conductivity of σtotal~1.13×10−4S/cm at room temperature, for a 50nm LLTO crystallite mean size addition.

Dielectric Properties and Energy Storage Densities of Poly(vinylidenefluoride) Nanocomposite with Surface Hydroxylated Cube Shaped Ba0.6Sr0.4TiO₃ Nanoparticles.

Ceramic-polymer nanocomposites, consisting of surface hydroxylated cube-shaped Ba0.6Sr0.4TiO3 nanoparticles (BST–NPs) as fillers and poly(vinylidenefluoride) (PVDF) as matrix, have been fabricated by using a solution casting method. The nanocomposites exhibited increased dielectric constant and improved breakdown strength. Dielectric constants of the nanocomposite with surface hydroxylated BST–NPs (BST–NPs–OH) were higher as compared with those of their untreated BST–NPs composites. The sample with 40 vol % BST–NPs–OH had a dielectric constant of 36 (1 kHz). Different theoretical models have been employed to predict the dielectric constants of the nanocomposites, in order to compare with the experimental data. The BST–NPs–OH/PVDF composites also exhibited higher breakdown strength than their BST–NP/PVDF counterparts. A maximal energy density of 3.9 J/cm3 was achieved in the composite with 5 vol % BST–NPs–OH. This hydroxylation strategy could be used as a reference to develop ceramic-polymer composite materials with enhanced dielectric properties and energy storage densities.

Polymerized Complex Synthesis and Effect of Ti Dopant on Magnetic Properties of LaFeO3 Nanoparticles.

Structure, characterization, and magnetic properties of Ti-doped LaFeO3 (LaFe(1-x)Ti(x)O3, x = 0, 0.1, 0.2, 0.3, 0.4 and 0.5) nanoparticles synthesized by polymerized complex method are investigated. All LaFe(1-x)Ti(x)O3 nanoparticles were successfully obtained from calcination of the precursor at 1050 degrees C in air for 2 h. The calcined LaFe(1-x)Ti(x)O3 samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersive X-ray analysis (EDX), X-ray photoelectron spectroscopy (XPS), X-ray absorption near edge spectroscopy (XANES) and vibrating sample magnetometry (VSM). The XRD and TEM results showed that all LaFe(1-x)Ti(x)O3 samples had a single phase nature with the orthorhombic structure. The valence states were mixed in the Fe3+ and Fe4+ state for Fe ions and Ti4+ state for Ti ions, as confirmed by XPS and XANES results. The weak ferromagnetic behavior with the highest magnetization (M) of -0.23 emu/g at 10 kOe was obtained for x = 0.4. The origin of the ferromagnetism (FM) for all LaFe1-x)Ti(x)O3 samples supports the magnetic coupling between Fe3+ and Fe4+ ions via double exchange (DE) interaction.

Zeta potential measurement on lithium lanthanum titanate nanoceramics

The zeta potential, isoelectric point, and agglomeration of Li0.5La0.5TiO3 (LLTO) nanoparticles dispersed in aqueous media at different ionic strengths have been studied. The zeta potential was determined from electrophoretic mobility measurements, according to Smoluchowski's equation, for Li0.5La0.5TiO3 suspensions in NaCl and KCl electrolytes with ionic strengths of 1, 10, and 100mmol/dm3. The isoelectric point (IEP), zeta potential (ζ), and the agglomeration were shown to strongly depend on the ionic strength of the Li0.5La0.5TiO3 aqueous colloidal suspension in both NaCl and KCl electrolytes, which allows the determination of the effects of environmental conditions for Li0.5La0.5TiO3 manipulation in aqueous colloidal systems. The suspensions of Li0.5La0.5TiO3 nanoparticles reach the IEP in the pH range of 3–5. The ζ of Li0.5La0.5TiO3 nanoparticles varied from positive to negative values with a pH increase, which allows for the control of the surface charge depending on the purpose. The pH range of 7–8 and an ionic strength ≤1mmol/dm3 are recommended as the most suitable conditions for both the LLTO colloidal shaping techniques application and the LLTO-based nanocomposite formation.

Influence of annealing temperature on Pb(Zr,Ti)O3 nanoparticles growth on multi-walled carbon nanotubes

We report the influence of annealing temperature on Pb(Zr,Ti)O3 nanoparticles (PZT NPs) grown on multi-walled carbon nanotubes (MWCNTs). The nanocomposites consist of PZT NPs and MWCNTs that were successfully prepared by using a sol-gel process, followed by an injection using a syringe filter and then by rapid thermal annealing. Field-emission transmission electron microscopy (FETEM) indicated that as the annealing temperature was increased, the shape and the crystallinity of the PZT NPs on the MWCNTs changed from an amorphous structure to the perovskite phase of PZT. Raman spectroscopy showed that the ratio of the intensity of G band to that of the D band, which indicates the crystal purity of the MWCNTs, decreased from 0.57 to 0.55 when the annealing temperature was increased from 500 to 700 °C. A separate distribution of elemental C in the PZT NPs on the MWCNTs annealed at 600 °C was directly observed via energy dispersive X-ray spectroscopy.

Optimization of nanocomposite gate insulators for organic thin film transistors

Nanocomposite gate insulators consisting of (Ba, Sr)TiO3 (barium strontium titanate; BST) nanoparticles and crosslinked poly(4-vinyl phenol) (PVP) polymers were fabricated. Well-dispersed nanocomposite films were prepared by optimizing the BST nanoparticle size sorting process (ultrasound crushing and centrifuge method). The size-sorted BST nanoparticles (∼30nm in size) were homogeneously mixed in the PVP host polymer in various BST contents, from 0 to 70wt%, to tune the dielectric constant (κ) of the resulting nanocomposite films. The composite films exhibit three-fold increase in the κ value from 3.9 to 11.3. The physical properties including leakage current and surface roughness of the composites were also measured as a function of the BST loading content and particle dispersion. The relationship between these properties and the electrical performance of the corresponding organic thin film transistor were explored.

Microstructure and optical properties of La0.5Sr0.5Ti1−xFexO3 nanoparticles prepared by thermal decomposition

La0.5Sr0.5Ti1–xFexO3 (x=0.005, 0.010, 0.015, and 0.020) nanoparticles were synthesized by thermal decomposition method at a calcination temperature of 900°C for 3h in air. The X-ray diffraction (XRD) results show the perovskite structure of all samples with the lattice type of cubic and the calculated crystallite size is in the range of 24–34nm. Transmission electron microscopy (TEM) bright field images show the agglomeration of nanoparticles with size of 100nm and larger. The corresponding selected-area electron diffraction (SAED) patterns show ring patterns of cubic structure which is in agreement with the XRD results. Optical absorption measurements using UV–visible spectroscopy show the absorption edge of La0.5Sr0.5TiO3 at ∼385nm and those of Fe-doped La0.5Sr0.5TiO3 nanoparticles at around 425nm. The energy gap is found to be decreased with increasing Fe concentration. The X-ray absorption spectroscopy (XAS) results of La0.5Sr0.5Ti1–xFexO3 nanoparticles indicate the oxidation states of 2+ and 3+ for Fe cations in all samples.

Improved magnetic and ferroelectric properties of Sc and Ti codoped multiferroic nano BiFeO3 prepared via sonochemical synthesis

The room temperature multiferroic properties of bulk BiFeO3 are not exciting enough for its application in devices. Here, we report the sonochemical synthesis of scandium and titanium codoped BiFeO3 nanoparticles which exhibit improved magnetic and ferroelectric properties at room temperature. The nanoparticles have been checked for phase purity and composition using powder X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS). The size and morphology of the nanoparticles have been confirmed using scanning electron microscopy (SEM), and both low and high resolution transmission electron microscopy (TEM/HRTEM). The breaking of the spin cycloid due to the smaller size and slight structural distortion caused by the doping has been found to be instrumental for the enhancement of multiferroic properties. The electrical polarization increases significantly in the case of BiFe(0.925)Sc(0.05)Ti(0.025)O3 nanoparticles. A marked reduction in the leakage current was seen compared to undoped BiFeO3. Magnetoelectric coupling was also observed in the BiFe(0.925)Sc(0.05)Ti(0.025)O3 sample. Our results demonstrate that codoping with Sc and Ti ions is an effective way to rectify and enhance the multiferroic nature of BiFeO3.

Performance of LST-GDC Composite Anodes for Solid Oxide Fuel Cells

La0.2Sr0.8TiO3 (LST) nanoparticles were fabricated by electrospinning. This material can be used as an alternative to the conventional nickel cermet anodes to solve the carbon deposition problem encountered in hydrocarbon fed solid oxide fuel cells (SOFCs). The phase pure LST material with perovskite structure has been obtained when the calcination temperature exceeds 800°C. The as-made LST nanoparticles were then sintered on ScSZ electrolyte at 1000°C to form nanoparticle-based LST anodes. In order to improve the electrochemical performance of the LST anode, Gd0.2Ce0.8O1.9 (GDC) precursor solution was infiltrated into the scaffolds formed by LST nanoparticles with different LST : GDC mass ratios. An optimal polarization resistance of 1.03 Ω cm2 has been achieved with the LST : GDC mass ratio of 1:0.50 when tested at 800 °C in 97% H2+3% H2O atmosphere. The result demonstrates the promising application of LST-GDC as SOFC anode material.