Tetragonal BaTiO3 Nanoparticles Research Articles

Self-polarization-enhanced oxygen evolution reaction by flower-like core–shell BaTiO3@NiFe-layered double hydroxide heterojunctions

A flower-like core–shell heterostructured oxygen evolution reaction (OER) electrocatalyst based on tetragonal BaTiO3 nanoparticles (t-BTO NPs) and NiFe-layered double hydroxide (NiFe-LDH) nanoarrays was prepared in this study. The influence from the self-polarization effect of t-BTO on the OER performance of NiFe-LDH is reported. Intriguingly, the OER activity of the t-BTO@NiFe-LDH heterojunctions in an alkaline media (1.0 M KOH) exhibited a low overpotential of 186 mV at 10 mA/cm2 and a low Tafel slope of 38.3 mV dec-1, which were far superior to those of the component materials: NiFe-LDH (267 mV and 94.8 mV dec-1) and t-BTO NPs (517 mV and 132.4 mV dec-1). Density functional theory (DFT) calculations revealed that the effective electronic modulation between t-BTO NPs and NiFe-LDH nanoplatelets narrowed the bandgap, promoted the electric conductivity, moderately raised Ed (i.e., energy level of the d-band center), optimized the adsorption ability of the oxygen-containing intermediates (*O, *OH, and *OOH), and induced an apparent reduction in the free energy barrier for the transformation from O* to OOH* in the t-BTO@NiFe-LDH heterojunctions. The PDOS result confirmed that t-BTO in the heterojunctions was easier to polarize, which can cause the rapid electron transfer in the OER process. In these heterostructures, the interface tension between BTO NPs and NiFe-LDH endowed BTO with easier self-polarization, thus leading to greater band tilting and faster electron transfer. Multiple synergistic effects of the flower-like core–shell t-BTO@NiFe-LDH heterojunctions enabled them with higher electrocatalytic activity. This work provides an in-depth understanding of the rational design of a high-efficiency, noble metal-free ferroelectric OER electrocatalyst based on the self-polarization of t-BTO NPs.

Enhancing Ultrasound-Assisted Iodine-Mediated Reversible-Deactivation Radical Polymerization by Piezoelectric Nanoparticles.

The development of mechanochemical tools for regulating the polymerization process has received an increasing amount of attention in recent years. Herein, we report the example of the mechanically controlled iodine-mediated reversible-deactivation radical polymerization (mechano-RDRP) using piezoelectric tetragonal BaTiO3 nanoparticles (T-BTO) as mechanoredox catalyst and alkyl iodide as the initiator. We demonstrated a more efficient mechanochemical initiation and reversible deactivation process than sonochemical activation via a mechanoredox-mediated alkyl iodide cleavage reaction. The mechanochemical activation of the C-I bond was verified by density functional theory (DFT) calculations. Theoretical calculations together with experimental results confirmed the more efficient initiation and polymerization than the traditional sonochemical approach. The influence of BaTiO3, initiator, and solvent was further examined to reveal the mechanism of the mechano-RDRP. The results showed good controllability over molecular weight and capacity for a one-pot chain extension. This work expands the scope of mechanically controlled polymerization and shows good potential in the construction of adaptive materials.

High-Performance Flexible Piezoelectric Nanogenerator Based on Electrospun PVDF-BaTiO3 Nanofibers for Self-Powered Vibration Sensing Applications

In the present era of intelligent electronics and Internet of Things (IoT), the demand for flexible and wearable devices is very high. Here, we have developed a high-output flexible piezoelectric nanogenerator (PENG) based on electrospun poly(vinylidene fluoride) (PVDF)-barium titanate (BaTiO3) (ES PVDF-BT) composite nanofibers with an enhanced electroactive phase. On addition of 10 wt % BaTiO3 nanoparticles, the electroactive β-phase of the PVDF is found to be escalated to ∼91% as a result of the synergistic interfacial interaction between the tetragonal BaTiO3 nanoparticles and the ferroelectric host polymer matrix on electrospinning. The fabricated PENG device delivered an open-circuit voltage of ∼50 V and short-circuit current density of ∼0.312 mA m-2. Also, the PVDF-BT nanofiber-based PENG device showed an output power density of ∼4.07 mW m-2, which is 10 times higher than that of a pristine PVDF nanofiber-based PENG device. Furthermore, the developed PENG has been newly demonstrated for self-powered real-time vibration sensing applications such as for mapping of mechanical vibrations from faulty CPU fans, hard disk drives, and electric sewing machines.

High-performance electrospun particulate matter (PM) filters embedded with self-polarizable tetragonal BaTiO3 nanoparticles

This study developed a novel transparent filter with a high particulate matter (PM) removal efficiency and low airflow resistance for use in windows. The main idea of this filter is to combine the ability of electrospun nanofiber (NF) structures to minimize airflow resistance with the unique self-polarizability of tetragonal BaTiO3 (t-BTO) nanoparticles, which enables the capture of PM through electrostatic interactions. Density functional theory (DFT) calculation predicted the self-polarization of t-BTO, and the presence of static electricity on the NF filters with t-BTO was confirmed by Kelvin probe force microscopy and electrostatic force measurement. Their PM removal efficiency and airflow resistance were dependent on the t-BTO loading and filter transparency. The filter with 20% t-BTO and 90% transparency exhibited a high PM removal efficiency (∼99.1% for PM10–2.5 and ∼98.9% for PM2.5) and a pressure drop of <70 Pa, indicating an extremely low airflow resistance. Moreover, its quality factor value reached ∼0.79 Pa−1, which far exceeds those of previously reported air filters (∼0.2 Pa−1). Further, accelerated long-term experiments for verifying the filter’s durability revealed that it exhibited a high PM removal performance and maintained a low airflow resistance despite a slight reduction in its performance. To enable the commercialization of our filter, the filter’s properties will be optimized based on the results of a field test under actual environments.

The application of modified nano-TiO2 photocatalyst for wastewater treatment: A review

ABSTRACT Because of the ever-growing world population and the burgeoning of economic advancements, solving both environmental and energy-driven challenges are of prime concern. In the view of the current scenario, photocatalyst as an environmentally friendly method has rapidly emerged due to its prominent function in the conversion of solar energy for overcoming two aforementioned serious challenges. Recently, numerous attempts have been carried out for enhancing the visible-light photoactivity by application of TiO2 as photocatalyst because of its extensive scope of employment in both environmental-related and energy regions. Nevertheless, the photocatalytic performance of TiO2 under visible-light illumination is seriously restricted by the absorption edge in the ultra-violet range and the rapid electron–hole recombination. Extensive research has been dedicated to bypassing the shortcomings of titanium dioxide and hence improving its photoactivity under visible light. To be more specific, some approaches for modification of TiO2 properties include tetragonal BaTiO3 nanoparticles, ultrasound-assisted preparation of rGO/TiO2 nanocomposite, BaTiO3/ZnO heterostructured photocatalyst, Sol pH-induced ZnO-TiO2 multi-phase composite, BaTiO3/g-C3N4 heterojunction, TiO2-zeolite nanocomposite, etc., were explored and developed. Moreover, in this review paper, the authors briefly evaluated various nano-TiO2 synthesis methods, such as sol-gel, hydrothermal, solvothermal, and mixed ones. Despite the excellent achievements and the improvements in this area, the probability of nano-TiO2 modification for highly efficacious photocatalyst systems has not been completely explored and its commercialisation still is problematic. As a result, still, intensive research efforts require to effectively overcome those challenges for reaching a bright future in the wastewater treatment process with minimum environmental adverse effects.

Effect of ferroelectric polarization field on different carrier migration in photoanode

Spontaneous polarization field in ferroelectric can improve the oxidation kinetics and photocurrent of a photoanode in photoelectrochemical water splitting. But the impact of ferroelectric polarization field on the migration of different charge carriers which have different mobility and diffusion length is still unknown. In this work, we synthesized tetragonal BaTiO3 nanoparticles by solvothermal method successfully and fabricated the hybrid photoanode composed by monoclinic WO3 and BaTiO3 for solar water oxidation. Density functional theory calculations showed that the mobility of electron was faster than that of the hole in WO3, and had a longer diffusion length. We demonstrated that the polarization field of ferroelectric had a greatly impact upon holes migration compared with electrons, thus the thin hybrid photoanode after poling by bias presented a significant improvement of photocurrent (210.5%) under the back-side illumination, and a remarkable augment of charge separation efficiency (94%) and oxidation kinetics (69%) at 1.23 V. Our work provided a deeper understanding of how ferroelectric polarization field affected the photoelectrochemical water oxidation and a general pathway towards enhancing minority carrier collection in photoanode.

Fabrication and Characterization of Piezoelectric Composite Nanofibers Based on Poly(vinylidene fluoride-co-hexafluoropropylene) and Barium Titanate Nanoparticle

Poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP)-based composite nanofibers containing different barium titanate (BaTiO3) nanoparticle contents of 10–60 wt% were fabricated by an efficient electrospinning. The piezoelectric performance of PVDF-HFP/BaTiO3 composite nanofibers under a periodic compressional pressure of ∼20 kPa was investigated by considering the BaTiO3 content and the electric poling. The X-ray diffraction patterns revealed the presence of piezoelectric tetragonal BaTiO3 nanoparticles in the composite nanofibers with PVDF β-form crystals. The SEM images demonstrated that the BaTiO3 nanoparticles were dispersed uniformly in the composite nanofibers at relatively low loadings of 10–20 wt%, but they formed aggregates at high loadings of 30–60 wt%. The piezoelectric performance of the composite nanofibers increased with the BaTiO3 content up to 20 wt% and decreased at higher BaTiO3 contents of 30–60 wt%, which results from the trade-off effect between the piezoelectric performance and the dispersibility of BaTiO3 nanoparticles in the composite nanofibers. Accordingly, the composite nanofibers with 20 wt% BaTiO3 exhibited maximum piezoelectric outputs such as voltage of ~9.63 V, current ~0.52 µA, and electric power of ~7892.2 nW. After the electric poling, the piezoelectric performance was further enhanced to ~11.69 V, ~20.56 µA, and ~1115.2 nW, which was high enough to light up a small LED bulb after rectification.

Facile Fabrication of Size-Tunable Core/Shell Ferroelectric/Polymeric Nanoparticles with Tailorable Dielectric Properties via Organocatalyzed Atom Transfer Radical Polymerization Driven by Visible Light

An unconventional but facile approach to prepare size-tunable core/shell ferroelectric/polymeric nanoparticles with uniform distribution is achieved by metal-free atom transfer radical polymerization (ATRP) driven by visible light under ambient temperature based on novel hyperbranched aromatic polyamides (HBPA) as a functional matrix. Cubic BaTiO3/HBPA nanocomposites can be prepared by in-situ polycondensation process with precursors (barium hydroxide (Ba(OH)2) and titanium(IV) tetraisopropoxide (TTIP)) of ferroelectric BaTiO3 nanocrystals, because precursors can be selectively loaded into the domain containing the benzimidazole rings. At 1200 °C, the aromatic polyamide coating of cubic BaTiO3 nanoparticles are carbonized to form carbon layer in the inert environment, which prevents regular nanoparticles from gathering. In addition, cubic BaTiO3 nanoparticles are simultaneously transformed into tetragonal BaTiO3 nanocrystals after high temperature calcination (1200 °C). The outer carbon shell of tetragonal BaTiO3 nanoparticles is removed via 500 °C calcination in air. Bi-functional ligand can modify the surface of tetragonal BaTiO3 nanoparticles. PMMA polymeric chains are growing from the initiating sites of ferroelectric BaTiO3 nanocrystal surface via the metal-free ATRP technique to obtain core/shell ferroelectric BaTiO3/PMMA hybrid nanoparticles. Changing the molar ratio between benzimidazole ring units and precursors can tune the size of ferroelectric BaTiO3 nanoparticles in the process of polycondensation, and the thickness of polymeric shell can be tailored by changing the white LED irradiation time in the organocatalyzed ATRP process. The dielectric properties of core/shell BaTiO3/PMMA hybrid nanoparticles can be also tuned by adjusting the dimension of BaTiO3 core and the molecular weight of PMMA shell.

Microstructures and piezoelectric performance of eco-friendly composite films based on nanocellulose and barium titanate nanoparticle

Eco-friendly nanocellulose-based composite films including different barium titanate (BaTiO3) nanoparticle contents were fabricated by an efficient aqueous suspension casting and following electric poling. The microstructures, dielectric/electrical property, and piezoelectric performance of the nanocellulose composite films were investigated as a function of the BaTiO3 content. The electron microscopic images demonstrated that the BaTiO3 nanoparticles were uniformly dispersed in the nanocellulose-based composite films. The X-ray diffraction results confirmed the presence of piezoelectric tetragonal BaTiO3 nanoparticles in the nanocellulose matrix with cellulose II phase. The dielectric constant and loss tangent of the composite films were found to increase and decrease with increasing the BaTiO3 content, respectively, which is favorable to achieve high piezoelectric outputs. On the other hand, the piezoelectric performance of the composite films increased with the BaTiO3 content up to 40 wt% and it decreased for the composites with 50–60 wt% BaTiO3, which results from the trade-off effect between the piezoelectric performance and the mechanical stiffness of BaTiO3 nanoparticle. Accordingly, the nanocellulose composite film with 40 wt% BaTiO3 was found to attain maximum piezoelectric outputs of voltage of ∼2.86 V, current of ∼262.4 nA, and electric power of ∼378.2 nW under a relatively low compressional stress of 5 kPa, which was high enough to charge microcapacitors after rectification.

Photocatalytic activity and dielectric properties of hydrothermally derived tetragonal BaTiO3 nanoparticles using TiO2 nanofibers

Tetragonal BaTiO3 nanoparticles have been hydrothermally synthesized using the electrospun TiO2 nanofibers as the Ti-source. Microstructural and compositional analyses have been carried out using XRD, SEM, TEM, XPS, and Raman spectroscopy. Characterization studies confirmed that the BaTiO3 nanoparticles had a tetragonal structure with an average particle size of 100 nm. Photocatalytic activities of the nanoparticles were investigated via the decolorization of methylene blue dye aqueous solutions under visible light and UV-A irradiations. The degradation efficiency reached to 13 and 35% after exposing to light for 60 min with visible and UV-sources, respectively. Effect of sintering temperatures on the dielectric properties was also investigated. Among all the sintering temperatures employed, 1473 K was the optimum sintering temperature for these ceramics in terms of high relative density (95.3%), high dielectric constant (3162 at 1 MHz), and low loss tangent (15 × 10−3 at 1 MHz). Experimental results showed that electrospun TiO2 fibers can be used as a precursor template to produce nano-scale BaTiO3 particles which are suitable for various applications such as photocatalysis and capacitors.

Synthesis of highly disperse tetragonal BaTiO3 nanoparticles with core–shell by a hydrothermal method

In order to synthesize of high-dispersion and tetragonal BaTiO3 (BT) nanoparticle, a hydrothermal method is used in a mixture of chloride metal sources and KOH with polyvinylpyrrolidone (PVP). The properties of BT–PVPs prepared by different reaction temperature and time are investigated via XRD, FE-SEM, DLS, FT-IR, and TEM to clarify the changes of the crystal phase, dispersion, and particle structure. The reaction is finished at 230 °C for 24 h and the critical reaction condition for that the crystal phase of the obtained BT particle changed from the cubic to the tetragonal is found to be 190 °C fixed in reaction time 24 h, and 9 h. During reaction the PVP on the BT surface decomposed to different form, and the PVP plays the role of dispersant in aqueous solution. By the hydrothermal condition of 230 °C for 24 h almost monodisperse BT–PVP with sizes of 83 nm and tetragonality (c/a) of 1.0062 were synthesized. The structure of nanoparticle, core (BT)–shell (PVP) was investigated by FT-IR and direct observed by TEM and the mechanism of particle growth and dispersion was discussed.

Study on effect of cubic- and tetragonal phased BaTiO3 on the electrical and thermal properties of polymeric nanocomposites

Polymer matrix nanocomposites based on polycarbonate (PC) and nanosized-cubic/tetragonal phases of barium titanate (BaTiO3) were fabricated using a solution method followed by hot pressing. The content of both cubic- and tetragonal phased BaTiO3 was varied from 0 to 50 wt%. For a given weight fraction, the dielectric constant of the nanocomposites containing tetragonal BaTiO3 is more than those of cubic BaTiO3 filled nanocomposites. Moreover, cubic BaTiO3/PC nanocomposites showed significantly lower dissipation factor than those of tetragonal BaTiO3/PC nanocomposites. The dielectric constant of the nanocomposites was found to be frequency-independent. The microhardness of the nanocomposites increased with increase in the BaTiO3 content (both cubic- and tetragonal-phased) compared to the pure matrix. Scanning electron microscopy showed better dispersion and good interaction of the tetragonal BaTiO3 nanoparticles in the matrix. The addition of cubic BaTiO3 nanoparticles significantly reduced the thermal stability of the nanocomposites compared to matrix while the addition of tetragonal BaTiO3 nanoparticles decreased it slightly. The glass transition temperature of the cubic BaTiO3/PC nanocomposites decreased significantly, whereas it reduced slightly for the tetragonal BaTiO3/PC nanocomposites.

Tetragonal BaTiO3 nanoparticles: An efficient photocatalyst for the degradation of organic pollutants

Photocatalytically active cubic and tetragonal phase BaTiO3 nanoparticles have been prepared by polymeric complex method. The prepared samples were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Photoluminescence spectroscopy (PL), Ultraviolet-visible (UV–vis) diffuse reflectance spectrophotometry (UV-DRS). In addition, the morphology of BaTiO3 was investigated using Transmission electron microscopy (TEM). The cubic and tetragonal phases of the prepared BaTiO3 were confirmed by XRD and Raman spectra. Methylene blue dye was used as a probe to evaluate the photocatalytic activities of cubic and tetragonal BaTiO3. This investigation revealed that BaTiO3 with tetragonal phase showed higher photocatalytic activity than that of the cubic BaTiO3. The photoluminescence result also supported the improved photocatalytic activity of tetragonal BaTiO3. However, a noticeable change in photocatalytic property could be observed on varying the amount of BaTiO3. The enhanced photocatalytic activity of tetragonal BaTiO3 makes it an excellent photocatalyst candidate for the degradation of pollutants.

Direct synthesis of ultrafine tetragonal BaTiO3 nanoparticles at room temperature.

A large quantity of ultrafine tetragonal barium titanate (BaTiO3) nanoparticles is directly synthesized at room temperature. The crystalline form and grain size are checked by both X-ray diffraction and transmission electron microscopy. The results revealed that the perovskite nanoparticles as fine as 7 nm have been synthesized. The phase transition of the as-prepared nanoparticles is investigated by the temperature-dependent Raman spectrum and shows the similar tendency to that of bulk BaTiO3 materials. It is confirmed that the nanoparticles have tetragonal phase at room temperature.

Effect of temperature and time on solvothermal synthesis of tetragonal BaTiO3

Tetragonal BaTiO3 nanoparticles are synthesized via solvothermal route in an ethanol water mixture. Ba(OH)2·8H2O is used as Ba precursor and TiO2 (P25 Degussa ∼25 nm, 30% anatase, 70% rutile) is used as Ti precursor in the Ba : Ti molar ratio 2 : 1. Effect of temperature and time study on solvothermal synthesis of BaTiO3 revealed that a moderate reaction temperature i.e. 185°C and longer reaction time favour tetragonal phase stabilization. Dissolution–precipitation appears to be the transformation mechanism for the crystallization of BaTiO3 from particulate TiO2 precursor.

Synthesis and Dispersion of Ultra-Small Binary and Ternary Metal Oxide Nanoparticles for Dielectric Thin Films

ABSTRACTFabrication of dielectric thin films using dispersions of ultra-small ZrO2and BaTiO3nanoparticles with a low-temperature processing is reported. Highly crystalline and monodisperse cubic-ZrO2and tetragonal-BaTiO3nanoparticles were synthesized using non-aqueous approach. Post synthesis, nanoparticle dispersions were realized through chemical modification of their surface. The obtained dispersions were then employed for the fabrication of homogeneous and densely-packed dielectric thin films, verified through scanning electron microscopy.

Hydrothermal Microwave: A New Route to Obtain Photoluminescent Crystalline BaTiO3 Nanoparticles

Hydrothermal microwave method was used as a new route to synthesize pure BaTiO3 (BT) nanoparticles at 140°C for 10 min under rapid reacting with stoichiometric Ba/Ti ratio. The crystalline products were characterized by X-ray powder diffraction (XRD) and the structure was refined by the Rietveld method from the tetragonal structure, which was supported by the Ti K-edge X-ray absorption near-edge structure (XANES). The pre-edge of Ti in the XANES spectra indicated that titanium ions are localized in a nonregular octahedron. Typical FT-Raman spectra for tetragonal BaTiO3 nanoparticles presented well-defined peaks, indicating a substantial short-range order in the system. However, a scattering peak at 810 cm−1 was attributed to the presence of lattice OH− groups, commonly found in materials obtained by hydrothermal process. Besides, the peak at 716 cm−1 can be related to eventual Ba2+ defects in the BaTiO3 lattice. BaTiO3 (BT) nanoparticles presented spherical morphology with a non-uniform distribution of pa...

Glycothermal synthesis and characterization of tetragonal barium titanate

Tetragonal barium titanate (BaTiO3) particles were synthesized at temperature as low as 220°C through glycothermal reaction by using Ba(OH)2·8H2O and amorphous titanium hydrous gel as precursors and 1,4-butanediol and water as solvent. XRD, DSC and Raman data support that glycothermal processing method provides a simple low-temperature route for producing tetragonal BaTiO3 nanoparticles without alkaline mineralizers. It is also demonstrated that the size and shape of BaTiO3 particles can be controlled by reaction conditions such as reaction temperature and various volume ratio of 1,4-butanediol/water. This processing method can fabricate BaTiO3 powders with narrow size distribution and low aggregation. In addition, BaTiO3 nanopowder with a Ba/Ti atomic ratio of 1.000±0.003 can be obtained in a reproducible manner with glycothermal process.

Size Tunable Synthesis of Highly Crystalline BaTiO 3 Nanoparticles using Salt-Assisted Spray Pyrolysis

Highly crystalline, dense BaTiO3 nanoparticles in a size range from 30 to 360nm with a narrow size distribution (σg = 1.2–1.4) were prepared at various synthesis temperatures using a salt-assisted spray pyrolysis (SASP) method without the need for post-annealing. The effect of synthesis temperature on particle size, crystallinity and surface morphology of the nanoparticles were characterized by X-ray diffraction and scanning/transmission electron microscopy. The nature of the crystalline structure was analyzed by Rietveld refinement and Raman spectroscopy. The particle size decreased with decreasing operation temperature. The crystal phase was transformed from tetragonal to cubic at a particles size of about 50nm at room temperature. SASP can be used to produce high weight fraction of tetragonal BaTiO3 nanoparticles down to 64nm in a single step.