Search

Barium titanate (BaTiO3)-polyvinyl butyral (PVB) composites at various weight concentrations were prepared via ultrasonic probe sonicator. The sonication was carried out at 20 kHz and 70% amplitude for about 2 h and BaTiO3 nanoparticles were dispersed well in the mixture of PVB/ethanol under probe sonication. As a microwave absorbent, the microwave absorbing properties of the BaTiO3 nanoparticle-PVB composites with different mixture ratios of 5 wt.% (RAM1), 10 wt.% (RAM2) and 15 wt.% (RAM3) BaTiO3 were investigated based on transmission line theory in the frequency range from 1 GHz to 14 GHz. The minimum reflection loss (RL) of the RAM1 reaches −3.47 dB at 5.57 GHz with a matching thickness of only 7.0 mm. For RAM2 with 4 mm and 4.2 mm thickness (tm), the RL values are less than −10 dB obtained in the frequency 10.3–13.4 GHz. The RAM3 composite with 15 wt.% BaTiO3 mixture ratio shows a minimum reflection loss of −43.8 dB at 11.01 GHz with a −15 dB bandwidth over the extended frequency range of 10.2–13.2 GHz for a thickness of 2.8 mm and −44.2 dB at 4.77 GHz for a thickness of 6.5 mm. [ABSTRACT FROM AUTHOR]

To develop high performance of polymer-based composites, the dispersion state and interfacial interaction of nano-fillers are two key issues to be considered. Herein, we report the surface decoration of basalt fibers (BF) with nano-sized barium titanate (BT) particles and their dielectric application in poly(ether sulfone)-based composite laminates (PBCLs) was investigated in detail. Firstly, the nano-sized BT particles uniformly deposited along the BF surface through a simple and effective solvothermal method, as confirmed by SEM and XRD measurement. Then, novel ternary dielectric polymer-based composite laminates, consisting of BT particles decorated BF and poly(ether sulfone) (BT-BF/PES), were fabricated by hot-pressing method. Compared to raw BF filled PBCLs, the SEM images of BT-BF fibers reinforced PBCLs showed that all the BT-BF fibers strongly adhere to the PES matrix, and obscure fiber/PES interfaces are present without visible boundaries, indicating a improved interfacial interactions in this case. Thus, the mechanical, thermal and dielectric properties of the resultant PBCLs were characterized and results indicated that the BF and BT particles show enhanced synergistic effects. Following this strategy, the flexural strength and dielectric constant of BT-BF/PES blend with 40 wt% of BT were increased by 28 and 350%, respectively, in comparison with those of BF/PES composite laminates. [ABSTRACT FROM AUTHOR]

In this paper, we report the synthesis of a multiferroic composite BaTiO 3 (BT) doped with Li 0.5 Fe 2.5 O 4 (LF) having chemical formulae (1- x ) BaTiO 3 + ( x ) Li 0.5 Fe 2.5 O 4 ( x  = 0, 0.05, 0.1, 0.15) using conventional solid state reaction method. We have focused on the structural and multiferroic properties of LF doped BT. We have characterized the grown composites by XRD, FESEM with EDAX, Piezoelectric coefficient, dielectric studies, A.C conductivity studies, magnetic properties and magneto-electric (ME) voltage coefficient. The XRD studies reveal the tetragonal nature of all composites. We have calculated the lattice parameters and the crystallite size from XRD pattern. The XRD patterns of all composites exhibit diphasic nature. The dielectric constant of all composites decreases steeply with an increase in the frequency and attains a nearly constant value in the high-frequency region. The variation of conductivity with the frequency reveals that at high-frequency region, the maximum conductivity decreases with an increase in the % of LF. The variation of conductivity with temperature reveals that the Curie temperature of the composite decreases as and when the % of LF is increased in BT. We have also studied the temperature dependence of the magnetization and the variation of the magneto-electric voltage coefficient (ME) with a magnetic field. The transition temperature and Neel temperature of all composites increased with increase in LF. The Magneto-electric (ME) coefficient of composites decreased with increase LF content. [ABSTRACT FROM AUTHOR]

As a photocatalyst, barium titanate (BaTiO 3 ) has shown a great potential in photocatalytic water splitting for hydrogen evolution. In this work, BaTiO 3 nanoparticles were synthesized at room temperature conditions under ambient pressure. The small particle size below 10 nm plays a key role in suppressing the recombination of photo-induced carriers, and thus promoting the photocatalytic activity. The photocatalytic hydrogen evolution rates of BaTiO 3 (BTO-R) synthesized at room temperature are 8 and 2.9 times that of commercial BaTiO 3 (BTO-C) in the presence and absence of triethanolamine (TEOA) as a sacrificial agent, respectively. This work provides a good example on size control, low-cost synthesis and photocatalysts' design. [ABSTRACT FROM AUTHOR]

Broom-like hierarchical structures of BaTiO 3 :Nd 3+ (1–11 mol %) nanophosphors (NPs) were fabricated via CTAB assisted solvothermal route. Controlled experiments namely, reaction temperature, surfactant concentration, pH and time duration were performed and its influences on morphology of the product was investigated. These conditions may tune the simple structures to broom-like hierarchical structures. The energy band gap (E g ) of the synthesized NPs were estimated to be ∼3.29–3.42 eV. Judd–Ofelt (J–O) intensity parameters were calculated by utilizing the photoluminescence emission spectra instead of normal absorption spectra. The CIE and CCT results indicates that the NPs exhibit intense blue light applicable for fabrication of cool LEDs. LFPs visualized by staining optimized NPs following powder dusting technique exhibits well defined level 1–3 ridge characteristics. Hence, it evidences versatility of the development techniques and NPs for visualization of LFPs with excellent sensitivity, selectivity, and without background hindrance. The obtained results evidence that the optimized NPs can be explored as a novel labeling marker for probing visualization of LFPs and solid state lightning. [ABSTRACT FROM AUTHOR]

We investigate polarization retention in 10 to 19 nm thick ferroelectric BaTiO3 (BTO) grown on Ge(001) by molecular beam epitaxy. The out-of-plane direction and reversibility of electric polarization were confirmed using piezoresponse force microscopy. After reverse-poling selected regions of the BTO films to a value P with a biased atomic-force microscope tip, we monitored relaxation of their net polarization for as long as several weeks using optical second-harmonic generation microscopy. All films retained reversed polarization throughout the observation period. 10 nm-thick BTO films relaxed monotonically to a saturation value of 0.9 P after 27 days and 19 nm films to 0.75 P after 24 h. Polarization dynamics are discussed in the context of a 1D polarization relaxation/kinetics model. [ABSTRACT FROM AUTHOR]

Abstract: Monodisperse BaTiO3 microspheres were synthesized using Ba(OH)2, a homemade amorphous TiO2 precursor, and dissolved CO2 as the raw materials. To dissolve sufficient CO2 in the mixing solution, the reaction process was carried out in air. Then, a BaCO3 layer, as a fixed barium source, was coated on the surface of the TiO2 precursor template through a hydrothermal process at 90°C. Furthermore, the BaCO3 reacted with the TiO2 precursor to form pure BaTiO3 through in situ conversion during subsequent heat treatment at 800°C. Compared to the commonly used acid soaking method for the removal of BaCO3 after hydrothermal treatment, the method combining in‐air mixing with a low hydrothermal temperature and heat treatment yielded BaTiO3 microspheres with a more monodisperse homogenous morphology, which have a greater potential in various applications. [ABSTRACT FROM AUTHOR]

The present study focuses on a novel approach to broaden the phase transition in Ba(Zr 0.2 Ti 0.8 )O 3 by the combined effect of oxygen annealing and La-doping. The (Ba 1-x La x )(Ti 0.8 Zr 0.2 )O 3 , Pb-free ceramics, with nominal compositions (x = 0.00, 0.01, 0.02 and 0.03) are synthesized in oxygen annealing atmosphere at 1673 K for 11 h using solid-state reaction method. While the X-ray diffraction confirmed the single phase formation, the secondary electron images revealed inhibited grain growth at a low concentration of La-doping but intermediate 2-dimensional grain growth at higher La-doping. The Raman peak appearing at 836 cm −1 indicates La-substitution at Ba-site and vacancies at Ti-sites. The temperature dependent dielectric permittivity exhibits a broad diffuse phase transition at T m = 230 K with a full width at half maxima (FWHM) of 289 K for 3 atomic % La-doped sample. The combined effect of oxygen annealing and La-doping results in an extremely broad diffuse phase transition. Such an extremely broad phase transition close to room temperature due to La-doping and oxygen annealing is useful for capacitor applications. [ABSTRACT FROM AUTHOR]

Barium titanate/hydroxyapatite (BaTiO 3 /HA) rod-like nanocomposites were fabricated by hydrothermal process at 140–180 °C for 12 h using the rod-like HA as a growth template, and BT precursor solution as a liquid phase. The structure was BaTiO 3 nanoparticles (average diameter of 6 nm) grown on the surface of HA rod like structure (diameter of ∼70 nm). The piezoelectric coefficient d 33 value of the material was 1.54 pC/N, being close to the body dry bones of 0.7 pC/N. The results of periodic DFT calculations and optimized geometry of CTAB and C 6 H 8 O 7 molecule obtained at the B3LYP/6-311 + g(d,p) level of theory in a suite of Gaussian 09 programs indicated CTAB and C 6 H 8 O 7 molecule were key to the formation of rod-like nanocomposites. Meanwhile, a solubility – crystallization mechanism was proposed to account for the nanocomposites. [ABSTRACT FROM AUTHOR]

BaTiO 3 (BT) ceramics with fine grains were sintered at an ultra low temperature of 180 °C by means of a novel sintering method named as cold sintering (CS). For CS, the hydrothermal precursor solutions were incorporated into the ceramic powders, and pressure was also applied during sintering. After annealing at 900 °C, the obtained samples exhibit dense microstructures and relative densities higher than 96%. The mean size of grains in the annealed samples is as low as 122 nm. Curie temperature of the ceramics is 116 °C. Dielectric constant and dielectric loss at 1 kHz and at room temperature are 2332 and 0.01, respectively. Compared to BT ceramics synthesized via a conventional solid-state sintering method, the BT ceramics in this work show increased peak width and decreased peak value on the dielectric constant-temperature curves around Curie temperature, suggesting diffuse phase transition character. The obtained BT ceramics show high breakdown strength (90 kV/cm), high energy storage density (1.45 J/cm 3 ), and high energy storage efficiency (85.6%). The results indicate that CS is an efficient method for low-temperature sintering BT ceramics with fine grains as well as good performance in energy storage. [ABSTRACT FROM AUTHOR]

The present research systematically investigated the novel low-temperature fabrication of a multi-walled carbon nanotube (MWCNT)/barium titanate nanocomposite using a two-step mixing technique. The synthesis was conducted using different amounts of MWCNT (0.25%, 0.5%, 1%, 2%, 4%, and 8% wt) with different compositions of (Bi 2 O 3 + B 2 O 3 ) as a sintering aid. Scanning and transmission electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, three-point bending strength, Vickers hardness indentation and Archimedean technique were used to characterize the as-synthesized specimens. It was found that the appropriate content of sintering aid (Bi 2 O 3 +B 2 O 3 ) strongly decreased the sintering temperature from 1200 °C to 950 °C. The results also revealed that any sintering aid with the optimum composition that included 30% (mol) Bi 2 O 3 was optimal for a sintering aid content of 6% (wt). Consequently, the highest values of the flexural strength and fracture toughness were achieved by applying the optimal amounts of MWCNT (1% wt) and sintering aid (6% wt). [ABSTRACT FROM AUTHOR]

In this paper, three BaTiO3 powders of various particle size distributions were obtained as a result of mechanical activation in the mixer mill. Green barium titanate pellets and cylindrical specimens were fabricated by both uniaxial and isostatic pressing methods. As a result of the application of different maximal sintering temperatures, the obtained materials were characterized by various average grain sizes: 0.8 μm, 20 μm and 31.0 μm. The basic properties of sintered pellets and cylinders were determined and the influence of materials average grain size on their Young’s modulus and compressive strength were determined through compression tests in a uniaxial testing machine, Zwick/Roell Z100. The elastic properties were similar for tested materials with a different grain size. However, the microstructure of BaTiO3 strongly influenced the compressive strength. [ABSTRACT FROM AUTHOR]

Perovskite oxides hosting ferroelectricity are particularly important materials for modern technologies. The ferroelectric transition in the well-known oxides BaTiO3 and PbTiO3 is realized by softening of a vibration mode in the cubic perovskite structure. For most perovskite oxides, octahedral-site tilting systems are developed to accommodate the bonding mismatch due to a geometric tolerance factor t = (A-O)/ [√2(B-O)] < 1. In the absence of cations having lone-pair electrons, e.g., Bi3+ and Pb2+, all simple and complex A-site and B-site ordered perovskite oxides with a t < 1 show a variety of tilting systems, and none of them become ferroelectric. The ferroelectric CaMnTi2O6 oxide is, up to now, the only one that breaks this rule. It exhibits a columnar A-site ordering with a pronounced octahedral-site tilting and yet becomes ferroelectric at Tc≈ 650 K. Most importantly, the ferroelectricity at T < Tc is caused by an order-disorder transition instead of a displacive transition; this character may be useful to overcome the critical thickness problem experienced in all proper ferroelectrics. Application of this new ferroelectric material can greatly simplify the structure of microelectronic devices. However, CaMnTi2O6 is a high-pressure phase obtained at 7 GPa and 1200 °C, which limits its application. Here we report a new method to synthesize a gram-level sample of ferroelectric Ca2-xMnxTi2O6, having the same crystal structure as CaMnTi2O6 and a similarly high Curie temperature. The new finding paves the way for the mass production of this important ferroelectric oxide. We have used neutron powder diffraction to identify the origin of the peculiar ferroelectric transition in this double perovskite and to reveal the interplay between magnetic ordering and the ferroelectric displacement at low temperatures. [ABSTRACT FROM AUTHOR]

Barium titanate (BaTiO 3 ) powders were synthesized through hydrothermal process with Ba(OH) 2 ·8H 2 O and TiO 2 . By increasing the feedstock concentration (FC) from 0.25 to 1.50 M, BaTiO 3 powders maintain a stable average particle size (~180 nm and ~6.4441 m 2 /g) with an increasing tetragonality ( c/a : 1.0065–1.0075). Johnson-Mehl-Avrami and standard reaction rate equations were adopted to analyze the kinetic process of BaTiO 3 formation. The reaction is governed by first-order and phase-boundary-controlled mechanism for 0.25 M and 1.50 M, respectively. Lower extent of reaction is believed to lead to the better tetragonality for BaTiO 3 powders fabricated with higher FC. On the other hand, the relative stable particle size is correlated with the unvaried nucleation frequency and grain growth rate with various FC. This work can provide a guideline to manipulate the properties of BaTiO 3 powders used in electronic industry. [ABSTRACT FROM AUTHOR]

A short-time decrease of the dispersion frequency by three orders of magnitude and its subsequent return to previous value was observed during investigations of dielectric dispersion of BaTiO3single crystal under influence of measuring electric field only. It is suggested that possible mechanism of this phenomenon is related to the dynamics of screening processes. [ABSTRACT FROM PUBLISHER]

In this work, we attribute the ferroelectric-relaxor crossover in BaTiO3-based solid solution to the percolation of the BO6octahedra occupied by solute atoms. BaTiO3-based solid solutions which are favorable for electrocaloric applications possess then a composition in the vicinity of the ferroelectric-relaxor crossover. For the first time, we consider a beneficial range of operational temperatures of EC devices based on these materials. [ABSTRACT FROM PUBLISHER]

Structure modification of tetragonal BaTiO 3 (t-BaTiO 3 ) and corresponding phase transition by microwave heating were investigated. The sample compound was heated by 1.8 kW power and 2.45 GHz frequency microwave irradiation under N 2 atmosphere in a short experimental duration of 14 min. The maximum temperature of the surface of the sample was 1115 °C. The structure of the microwave irradiated BaTiO 3 was then analyzed by employing X-ray diffraction (XRD), Rietveld refinement analysis, Raman spectroscopy, and field emission scanning electron microscopy techniques. From XRD and Rietveld refinement analysis, the microwave irradiated BaTiO 3 sample was composed of hexagonal 89%, cubic 5% and tetragonal 6%. Due to the direct internal heating mechanism of microwaves, the core temperature of the sample might be higher than the phase transition temperature. The magnetic behavior of the sample was investigated using a vibrating sample magnetometer. The results indicated that the microwave irradiated BaTiO 3 exhibited mixed magnetism: ferromagnetic nature at low applied magnetic fields and diamagnetic nature at high applied magnetic fields. [ABSTRACT FROM AUTHOR]

Using the three-dimensional space coordinate transformation approach, orientation dependence of the longitudinal magnetoelectric coefficient αE33 in tetragonal BaTiO3/face centered cubic (fcc) CoFe2O4 composites was calculated in arbitrary directions. A clamp-free condition is used in the calculation. The direction along which αE33 is maximum is a function of psij, pεij, dij of piezoelectric phase and msij, mμij, qij of magnetostrictive phase referred to the crystallographic coordinate system. For a fixed CoFe2O4 orientation, the maximum αE33 lies along [001] axis of BaTiO3. And for a fixed BaTiO3 orientation, the maximum αE33 lies along [001] axis and a large αE33 also lies along [11l] (l > 0) of CoFe2O4. BaTiO3 || [001]/CoFe2O4 || [001] combination has the maximum αE33 which is 641 mV/cm Oe. The maximum αE33 is about 2 times of that of random orientated materials. Volume fraction is quite independent of orientation changes of both piezoelectric and magnetostrictive phases and the volume fraction for magnetostrictive phase f around 0.76 obtains the largest αE33. Our results suggest an approach of significantly enhancing magnetoelectric coefficient of composite multiferroic materials through crystal orientation and texture engineering. [ABSTRACT FROM AUTHOR]

Using the three-dimensional space coordinate transformation approach, orientation dependence of the longitudinal magnetoelectric coefficient αE33 in tetragonal BaTiO3/face centered cubic (fcc) CoFe2O4 composites was calculated in arbitrary directions. A clamp-free condition is used in the calculation. The direction along which αE33 is maximum is a function of psij, pεij, dij of piezoelectric phase and msij, mμij, qij of magnetostrictive phase referred to the crystallographic coordinate system. For a fixed CoFe2O4 orientation, the maximum αE33 lies along [001] axis of BaTiO3. And for a fixed BaTiO3 orientation, the maximum αE33 lies along [001] axis and a large αE33 also lies along [11l] (l > 0) of CoFe2O4. BaTiO3 || [001]/CoFe2O4 || [001] combination has the maximum αE33 which is 641 mV/cm Oe. The maximum αE33 is about 2 times of that of random orientated materials. Volume fraction is quite independent of orientation changes of both piezoelectric and magnetostrictive phases and the volume fraction for magnetostrictive phase f around 0.76 obtains the largest αE33. Our results suggest an approach of significantly enhancing magnetoelectric coefficient of composite multiferroic materials through crystal orientation and texture engineering. [ABSTRACT FROM AUTHOR]

The composition, structure, reflection spectra, and radiation stability of BaTiO 3 coatings obtained by the detonation spraying method were investigated for the first time. Samples were characterized by using X-ray diffraction (XRD), high resolution scanning electron microscopy (SEM), and a spectrophotometry. It has been found that other compounds during spraying do not form, except BaTiO 3 . The coatings from BaTiO 3 powder with thickness up to 300 μm were formed on aluminum alloy substrates. It has been found that the reflectance in the visible and near infrared region of the spectrum of these coatings is comparable with the reflectivity of BaTiO 3 powders. The radiation stability of the sprayed coatings is much higher in comparison with the compressed BaTiO 3 powders and paints based on them. The radiation stability increasing of detonation coating in comparison with two other types of coatings is defined by regularity of absorption centers formation on the surface. The detonation spraying allows to get reflective smart coatings based on BaTiO 3 powders needed for thermal stabilization of spacecraft and other objects. [ABSTRACT FROM AUTHOR]

The conditions for the topochemical transformation of variously sized Bi4Ti3O12 template plates into BaTiO3 particles were studied in order to control their morphology, crystal structure, and preferential orientation. In the transformation from sub-200 nm- and µm-sized template plates in the presence of surplus BaCO3 (Bi4Ti3O12/BaCO3 = 1:10), the final BaTiO3 particles retained a memory of the precursor size when the conversion reaction in the molten salt (NaCl/KCl) occurred at 660 and 900 °C, respectively. In both cases the side length of the template was well preserved, while the thicknesses of the final BaTiO3 plates were larger compared to those of the templates. The morphology of the BaTiO3 particles formed from micrometer-sized Bi4Ti3O12 plates at 660 °C did not closely resemble the template shape because of the exfoliation and disintegration processes. Through the transformation of sub-200 nm Bi4Ti3O12 plates at 900 °C the formed BaTiO3 particles grew by Ostwald ripening, and thus also the shape of the final perovskite particles did not retain a memory of the template. We confirmed by Raman spectroscopy and X-ray diffraction that the BaTiO3 plates formed at 900 °C exhibited a higher tetragonality than those prepared at 660 °C. Ferroelectric hysteresis and piezoelectric butterfly curves, as obtained using a piezo-force microscope, indicated the significant ferroelectric response of [001] preferentially oriented micrometer-sized and sub-micrometer-sized BaTiO3 plates. [ABSTRACT FROM AUTHOR]

Perovskite barium titanate (BaTiO 3 ) nanocomposite thin film has been prepared using spin coating technique. Surface morphological, structural, compositional and optical properties of the film were investigated by various techniques such as SEM, XRD, TEM, EDS, UV-Spectroscopy, Raman spectroscopy and FTIR. SEM images showed the macroporous cubic structure of the film. The minimum crystallite size was evaluated as 11 nm by XRD and confirmed by TEM. Band gap of BaTiO 3 was evaluated as 3.9 eV. Raman Spectroscopy confirmed the formation of BaTiO 3 at 540 cm −1 . LPG sensings were carried out for vol.% 0.5–4 of LPG and sensor was found robust for the detection of LEL for LPG also. [ABSTRACT FROM AUTHOR]

One-dimensional BaTiO3 nanomaterials have important applications in nano-ferroelectric devices, and their high-quality synthesis is a hotspot in the field of chemistry of materials. In this work, single-crystalline perovskite BaTiO3 nanorods have been prepared by a two-step molten salt method. The conversion process and the topochemical mechanism were investigated based on XRD, DSC, SEM and TEM analysis. Firstly, one dimensional BaTi2O5 nanocrystallites have been synthesized in a molten environment and the self-polarization effect is responsible for the growth direction of [0 2 0]. Then, using these oriented BaTi2O5 monoclinic nanorods as templates, BaTiO3 perovskite nanorods have been further constructed through the topochemical reaction, in which all edge-sharing [TiO6] octahedra converted into corner-sharing modes to obtain the minimum energy state. One-dimensional morphology of BaTiO3 can only be obtained at a low calcination temperature, because at a high temperature, it will decompose into nanoparticles. This topological method is facile and can be developed to construct other orientated functional materials. [ABSTRACT FROM AUTHOR]

Ternary thermoplastic systems based on poly(vinylidene fluoride), PVDF, filled with barium titanate, BaTiO3, submicrometric particles and carbon nanotubes, CNT, were prepared. Their structure and morphology were studied as a function of composition and finally correlated with thermal and mechanical properties. High energy ball milling, HEBM, under cryogenic conditions and subsequent hot pressing were used to obtain films with quite uniform dispersion of the nanofillers. The presence of BaTiO3 particles and CNT did not modify the thermodegradation mechanism of the PVDF. However, enough amount of BaTiO3 seemed to inhibit the volatility of the products of pyrolysis, hindering the decomposition of PVDF. The presence of CNT favored the PVDF thermodegradation probably due to improved heat transmission by an increase in the thermal conductivity. Variations in PVDF thermal transitions were more dependent of processing conditions. Improvements in the mechanical properties of PVDF were ascribed to a reinforcing effect of the fillers. This effect only happened below the fraction of percolation of CNT, pointing out that CNT reinforce through an optimum load transfer from the PVDF matrix to the nanofillers. POLYM. COMPOS., 38:227-235, 2017. © 2015 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

Barium titanate (BaTiO 3 ) was produced from an barium-titanate-peroxo-hydroxide precursor material in NaCl-KCl and Na 2 SO 4 -K 2 SO 4 salt mixtures or fluxes at temperatures up to 1080 °C via the molten-salt synthesis (MSS) method. Beside the different salt mixtures several other parameters were studied to determine the effect on the particle morphology. A relatively fast heating rate and a relatively high salt to precursor ratio resulted in a highly faceted morphology. The effect of the salt flux was clearly seen in the morphology of BaTiO 3 obtained by MSS at 1080 °C. Cube-shaped particles were observed for the chloride-flux-grown BaTiO 3 while hexagonal-shaped flat particles were observed for the sulfate-flux-grown BaTiO 3 . BaTiO 3 particles produced in the chloride-flux were either {1 0 1} or {0 0 1} faceted. The hexagonal surface of the sulfate-flux-grown BaTiO 3 was {1 1 1} faceted. [ABSTRACT FROM AUTHOR]

The crystal structure modifications of BaTiO3induced by cobalt doping were studied. The polycrystalline (1 −x)BaTiO3+xCo2O3samples, withx≤ 10 wt.%, were prepared by high temperature sintering conventional method. According to X-ray phase and structural characterization, performed by full-profile Rietveld refinement technique, all synthesized samples showed tetragonal symmetry perovskite structure with minor amount of parasitic phases. Pure single-phase composition has been detected only in the low level of doping BaTiO3. It was indicated that substitution of Co for the Ti sites in the (1 −x)BaTiO3+xCo2O3series led to decrease of tetragonality (c/a) of the BaTiO3perovskite structure. This effect almost vanished in the (1 −x)BaTiO3+xCo2O3samples with nominal Co content higher than ∼1 wt.%, in which precipitation of parasitic Co-containing phases CoO and Co2TiO4has been observed. Based on the results, the solubility limit of Co in Ti sub-lattice in the (1 −x)BaTiO3+xCo2O3series is estimated asx= 0.75 wt.%. [ABSTRACT FROM AUTHOR]

Single phased Sr substituted BaTiO ceramics were synthesized by a sol-gel route and were found to crystallise in tetragonal symmetry with P space group using rietveld refinement. With increase in Sr content the tetragonality was reduced to pseudocubic and the Curie temperature ( T ) decreased with a rate of 3.33 K/mol %. This transition temperature has been determined by studying the thermal evolution of Cole- Cole diagrams (ε'' vs ε'). Effects of Sr content ( x) and sintering time (4 and 8 h) on density, crystalline structure and piezoelectric properties were also investigated. [ABSTRACT FROM AUTHOR]

A novel perovskite structured barium titanate (BaTiO 3 ) nanopowder was successfully synthesized at low temperature by a facile and an inexpensive microwave method. The synthesized nanosphere shaped BaTiO 3 was analyzed using advanced characterization techniques such as X-ray diffraction analysis, Fourier transform infrared, Micro Raman, Scanning electron microscope with energy dispersive analysis and ultraviolet-visible diffuse reflectance spectroscopic techniques. Photocatalytic dye degradation study was carried out using newly synthesized BaTiO 3 catalyst. The synthesized sphere shaped barium titanate nanopowders effectively degrade the various dyes such as Methylene Blue (MB), Malachite Green (MG) and Alizarin Red S (ARS) under UV light irradiation. The band gap energy of synthesized BaTiO 3 was calculated by UV-DRS spectra using kubelka-Munk equation. The higher dye decomposition efficiency of nearly 100% was successfully achieved by BaTiO 3 (BT10) nanosphere which was prepared using 10 min microwave irradiation. [ABSTRACT FROM AUTHOR]

The promoting effect of water in different states of aggregation on the transformation processes in oxide mixture was studied in case of BaTiO 3 formation. The reaction between barium and titanium oxide was carried out in liquid, in gaseous and in supercritical water. The state of aggregation of the reaction medium had an influence on the degree of transformation of the reagents and on the characteristics of produced BaTiO 3 such as the crystal size, the content of volatile impurities and sinterability. On the basis of comparative investigation it was concluded that the synthesis in supercritical water appeared to be the most effective way for production of pure fine-crystalline BaTiO 3 for the ceramics preparation. [ABSTRACT FROM AUTHOR]

The polycrystalline samples of gadolinium ortho-ferrite (GdFeO 3 ) modified barium titanate (BaTiO 3 ) ceramics have been prepared by a chemico-thermal route. The effect of sintering temperature on electrical (dielectric, impedance and conductivity) and magnetic characteristics of the material has been observed. The sintering temperature does not affect the crystal structure. With the increase in sintering temperature, the dielectric constant, loss tangent and the diffusive nature of the phase transition is found to increase. Impedance characteristics and transport properties of the material indicate a decrease in effective resistance of the sample with an increase in sintering temperature. The magneto-electric coefficient of the material was also found to decrease with increase in sintering temperature. [ABSTRACT FROM AUTHOR]

To investigate the material design of inks for high performance dielectric thin films constructed using BaTiO 3 nanoparticles and polymer resin, the BaTiO 3 mono-dispersed sol and the polymer solution were simply mixed and stirred to obtain the composite ink. The polymers chosen were cyanoethyl pullulan (CEP) and an epoxy. The dielectric constant of the BaTiO 3 /CEP composite thin film was higher than that of the BaTiO 3 thin film and the BaTiO 3 /epoxy composite thin film because the dielectric constant of CEP is higher. Conversely, the resistance of the BaTiO 3 /epoxy composite thin films to frequency change was clearly greater than that of the BaTiO 3 /CEP composite thin films. Thus, the polymer component strongly affected the performance of dielectric constant. These results offer an important method for designing the dielectric composite ink for the development of thin film capacitors. [ABSTRACT FROM AUTHOR]

The reaction of Ba(NO3)2with TiO2was studied by thermogravimetric (TG) and differential scanning calorimetric (DSC) techniques up to 1000°C and in nitrogen atmosphere. It was found that the formation of BaTiO3takes place above 600°C. BaTiO3powder was prepared by calcination of Ba(NO3)2and TiO2precursor mixture at 800°C for 8 h. X-ray diffraction analysis of the synthesized BaTiO3confirmed the formation of tetragonal phase. Average crystallite size was found to be 44 nm, For the electrical and morphological characterization pellets of the obtained powder were sintered at 1000 °C for 12 h. Scanning electron micrograph (SEM) exhibits spherical and rod shaped grains. The dielectric constant, dissipation factor, complex plane impedance and ac conductivity of the sintered pellet has been measured in the temperature range of 40–600°C and frequency range of 100 Hz–2 MHz. DC conductivity of the sample was obtained from the impedance data. The conductivities (both ac and dc) and relaxation time (τ) exhibit two regions of temperature dependence, namely region I, which represents (280–450°C) and region II, which governs (450-600°C). Conduction and relaxation in both the temperature regions are explained in terms of hopping of electrons and doubly ionized oxygen vacancies (VO••). [ABSTRACT FROM PUBLISHER]

As highly integrated circuits are demanded for high-performance electric devices, small sizes of barium titanate (BaTiO3) as a dielectric material are desirable for the application of multilayer ceramic capacitors. Since the small sizes of the particles degrade the dielectric property, especially below a certain critical size, understanding the probable cause is significant for the high-performance capacitors. Here, we have demonstrated nanosized BaTiO3 with average size below 30 nm and a uniform size distribution. High-resolution transmission electron microscopy (TEM) shows that the as-synthesized BaTiO3 contains intragranular pores. We have analyzed the correlation between the intragranular pores inside nanoparticles and their phase ratio of cubic and tetragonal. We have found that the presence of the intragranular pores affects low tetragonality of BaTiO3 particles, and the intragranular pores are generated by the accumulation of hydroxyl groups during hydrothermal reaction. Formation and accumulation of intragranular pores have been investigated by ex-situ synchrotron X-ray diffraction and TEM analysis, suggesting the phase evolution model of nanosized BaTiO3. [ABSTRACT FROM AUTHOR]

Preisach-based method was used to characterize a series of BaTiO3hysteresis loops with varying external field frequencies. A stochastic adjustment of hysterons' weight was performed to obtain the Preisach densities. These densities, in representing the hysteresis responses, were characterized with three key parameters of the 3-dimensional hyperbolic-like distribution. One of the parameters relates directly to coercivity, while the other two concurrently represent polarization derivatives close to the coercivity, and emphasize an adaptability of the material to the external field around the main body of the loops. Thus, this approach can be extended to characterize other series of hysteresis loops to study changes of material responses influenced by varying external field frequency factor. [ABSTRACT FROM PUBLISHER]

Lanthanum doped barium titanate was nitridated by thermal ammonolysis with a newly designed reactor, which performs extended efficiency to supply ammonia with less decomposition at elevated temperatures above 600 °C. The kinetics of nitrogen-uptake was studied systematically at elevated temperatures. Nitrogen-content, thermal stability and crystallographic phase of nitridated lanthanum doped barium titanate were characterized by several techniques. The final nitrogen-content of nitridated lanthanum doped barium titanate was much higher than the content of lanthanum, resulting in the formation of oxygen vacancies compensating the additional negative electrical charge of nitrogen anions occupying regular oxygen sites in the lattice. Through thermal ammonolysis, strongly reducing conditions because of the decomposition of ammonia generating hydrogen gas causes the formation of barium orthotitanate as a secondary phase. Ammonolysis temperature below 800 °C and suppression of thermal decomposition of ammonia gas are essential to realize a nitridated lanthanum doped barium titanate as a single phase. [ABSTRACT FROM AUTHOR]

Micro-honeycomb barium titanate (BaTiO 3 ) ceramics, which have uniformly distributed one-dimensional pore channels, were prepared by freeze-casting suspensions of hydrothermally synthesized BaTiO 3 nanopowder with a particle size of 100 nm. The effects of sintering schedules such as sintering temperature and holding time on pore size distribution, porosity, pore wall density and grain size were studied. The grain size on the pore wall of BaTiO 3 is around 1–2 μm after two-step sintering. The crystallographic structure of all samples was tetragonal phase regardless of the sintering schedules. Ferroelectric domains were shaped in a stripe and the domain width obviously increased after polarization. The micro-honeycomb BaTiO 3 sintered at lower temperature or shorter holding time showed larger piezoelectric coefficient d 33 and smaller dielectric constant ε r . [ABSTRACT FROM AUTHOR]

Iron (Fe) doped barium titanate nanoceramics (BaTi 1- x Fe x O 3 ) were synthesized through sol-gel auto combustion route. The effect of Fe doping on the structural, morphological, ferroelectric and magnetic properties was systematically studied. X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopic measurements showed that the synthesized samples have a tetragonal dominant structure with the presence of intermediate hexagonal phase for higher Fe content ( x =0.4 and 0.5). Accurate values of average crystallite size ( D ) and lattice parameter ( a and c ) were calculated by the Williamson-Hall (W-H) analysis and Nelson-Riley extrapolation function (N-R) respectively. The calculated average crystallite size ( D ) of the prepared samples is in the 17–27 nm range. The surface morphology of the grains was examined by field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). Compositional stoichiometry was confirmed by energy dispersive spectrum (EDS) analysis. The ferroelectric property was studied by a P-E hysteresis loop. Magnetic and ferroelectric hysteresis loops are strongly influenced by Fe ion doping concentration due to creation of oxygen vacancies. The saturation electric polarization decreases with the increasing of Fe ion doping concentration. The pure BaTiO 3 prepared exhibits diamagnetism. Simultaneously, magnetization of doped compositions is enhanced with increasing of Fe ion concentration. Room temperature ferromagnetism is also observed in Fe doped BaTiO 3 samples. This anomaly in the magnetic behavior can be explained in terms of the changes in the oxidation state exchange interactions of ions such as the Fe 3+ - to - Fe 4+ change induced by oxygen vacancies. A divergence was observed in the temperature dependence of the field cooling (FC) and zero-field cooling (ZFC) magnetization curves, indicating a spin-glass behavior arising from micro-magnetic state, i. e. the mixing of ferromagnetic and antiferro-magnetic phases. The ferromagnetic properties are predominant below 50 K and increases with the Fe doping concentration. [ABSTRACT FROM AUTHOR]

The effect of the synthesis method (hydrothermal and sol-gel) on the properties of BaTi 0.8 Cu 0.2 O 3 perovskites as catalysts for NOx and soot removal has been analyzed. X-ray powder diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS), ICP-AES, N 2 adsorption at −196 °C, Raman spectroscopy, Field Emission Scanning Electron Microscopy (FESEM) and temperature programmed reduction with hydrogen (H 2 -TPR) have been used for catalysts characterization. To test their catalytic activity, NOx storage and soot combustion temperature programmed reaction tests have been carried out. The results allow to conclude that the synthesis method determines the position of copper on the perovskite structure and, therefore, the catalytic applications. When the hydrothermal method is used the copper is highly dispersed on the perovskite surface, obtaining a catalyst with a high activity for the NO to NO 2 oxidation reaction, which can be used as oxidation catalyst for soot removal. Nevertheless, using the sol-gel method, copper is incorporated into the perovskite structure and, consequently, the catalyst presents a high NOx storage capacity [ABSTRACT FROM AUTHOR]

Barium titanate (BaTiO) is a common ferroelectric material with perovskite structure widely used for the production of a variety of electro-optical devices. When doping with rare earth elements, very interesting characteristics can be attributed to BaTiO. Among the methods used to synthesize BaTiO, wet chemical approaches are the most suitable for preparing homogenous and pure nanostructured materials. In this sense, the present article aims to summarize the state-of-the-art of the most relevant wet chemical routes for the synthesis of nanocrystalline BaTiO doped with rare earth (RE) ions (BaTiO:RE), which include the following: sol-gel, sol-emulsion-gel, Pechini, solvothermal/hydrothermal, and co-precipitation methods. The influence of each method on morphology and particle size, as well as on the dielectric and/or luminescent properties of the powders is discussed. [ABSTRACT FROM AUTHOR]

Dielectric barium titanate nanoparticles are essential to develop reliable microelectronic devices. However, their dielectric properties largely depend on the synthesis method used. Hence, we developed BaTiO 3 nanoparticles by various synthesis methods seeking to compare and evaluate their crystal structure, size, and homogeneity. Syntheses were carried out by four distinct synthesis methods: polymeric precursor (Pechini), electrochemical, hydrothermal and microwave-assisted hydrothermal. X-ray diffraction and Raman spectroscopy analysis revealed the formation of barium titanate in cubic and tetragonal structures. The nanoparticles synthesized have BET superficial areas varying in the range 10–15 m 2 g −1 . Pechini method propitiated the formation of smaller particles than the other methods, i.e. 44.0 ± 15 nm. By the electrochemical synthesis method the particles were obtained with 67.0 ± 20 nm of diameter, with large distribution in particle size. The use of hydrothermal methods conducted to various particle size distributions; while particles of 180.0 ± 60 nm were formed using conventional hydrothermal synthesis, smaller particles (66.0 ± 16 nm) were formed using the microwave-assisted hydrothermal synthesis in lower reaction times (six fold). All four methods were effective to synthesize crystalline BaTiO 3 nanoparticles, with different sizes and structural characteristics. Thus, the choice of the suitable synthesis method will depend on the desired properties of the BaTiO 3 nanoparticles. [ABSTRACT FROM AUTHOR]

In this study, 3-Aminopropyltriethoxysilane (KH550) with polar amino groups is applied to modify the surface of Barium titanate (BaTiO) particles. When volume fraction of BaTiO further increases to 50 vol%, the dielectric constant and loss of HDPE control increase from 2.5 and 0.02 to 18.5 and 0.10 at 10 MHz, respectively, with the volume resistivity of HDPE control decreasing from 3.6 × 10 Ω m to 3.5 × 10 Ω m. The increased amount of modified BaTiO can increase the flexural strength and modulus HDPE composites from 8 and 90 MPa to 14 and 780 MPa, respectively. However, the increase of modified BaTiO can restrict mobility of HDPE chains and decrease the crystallinity of HDPE composites. [ABSTRACT FROM AUTHOR]

In this study, we systematically investigated the composition dependence of the phase structure, microstructure, and electrical properties of (Ba0.94Ca0.06)(Ti1–xMx)O3 (M = Sn, Hf, Zr) ceramics synthesised by the conventional solid-state reaction method. The phase boundary type strongly depends on the composition, and then different electrical properties were exhibited. The addition of Hf and Zr can more quickly shift phase transition temperatures (TR–O and TO–T) to a higher temperature with respect to Sn, leading to the formation of different phase boundaries. In addition, different phase boundaries can also be affected by their doped contents. The R–O and O–T phase boundaries can be shown in the Sn-doped ceramics with x = 0.10, and the R–O phase boundary can exist in the Hf (x = 0.07) or Zr (x = 0.075)-doped ceramics. A high piezoelectric property of d33 = 600 pC N−1 can be achieved in the Sn-doped ceramics due to the involvement of converging R–O/O–T phase boundaries, an enhanced ferroelectric performance with Pr = 14.54 μC cm−2 and Ec = 1.82 kV cm−1 can be attained in the Zr-doped ceramics, and Hf would benefit from obtaining a large strain behaviour (∼0.20%). We believe that the electrical properties and the related physical mechanisms of BaTiO3-based ceramics can be well unveiled by studying their chemical modification behavior. [ABSTRACT FROM AUTHOR]

Polycrystalline samples of Li and Bi co-substituted BaTiO were synthesized using microwave assisted heating of the starting materials. This synthesis process extraordinarily reduced the processing time to 40 min, which includes heating and the dwell durations. The room temperature powder X-ray diffraction patterns reveals that the obtained compounds were of pure BaTiO phase (BTO). The structural, morphological and dielectric behaviour of these compositions were studied. Improved dielectric properties have been observed with the substitute of Bi and Li. It is interesting to note that the loss tangent of the co-substituted compositions are lower than that of the parent composition and it decreases approximately with increasing extent of co-substitution. This property is quite useful to develop this material further for capacitor applications. The transition temperature has shifted from 120 °C of pure BaTiO towards higher temperatures to 150, 160 and 175 °C with (Bi, Li) where x = (0.02, 0.04 and 0.08), respectively of co-substitution BaTiO. The change is linear with the degree of co-substitution. [ABSTRACT FROM AUTHOR]

Microwave absorbing composites composed of both multi-walled carbon nanotubes (MWCNTs) and Barium titanatena (BaTiO) nanoparticles as absorbers were prepared by sol-gel method. The structure and morphology of the BaTiO/MWCNTs nanocomposites were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). The complex permittivity and permeability of the BaTiO/MWCNTs nanocomposites were measured and then the reflection loss (RL) was calculated in the frequency range of 1-18 GHz. The sample ω = 2.5 % (the mass fraction of MWCNTs is denoted as ω hereafter) has the minimum reflection loss of −34.4 dB at 15.1 GHz compared with the other samples at the same thickness of 1.4 mm and the effective bandwidth(RL < −10 dB) is even wider than 3.5 GHz, ranging from 13.8 to 17.4 GHz. Furthermore, the sample ω = 2.5 % can reach −47.9 dB at 7.1 GHz with the thickness of 7.0 mm and the effective bandwidth almost covers 10 GHz with the thickness ranging from 1.4 to 9.0 mm. The obtained BaTiO/MWCNTs nanocomposites may become an ideal microwave absorber with thin thickness, broad bandwidth and strong absorption. Good absorption properties at a low MWCNTs loading provide an added advantage in terms of ease of processability, MWCNTs filler saving and overall process economics. [ABSTRACT FROM AUTHOR]

The Er3+/Yb3+co-doped 0.94Na0.5Bi0.5TiO3-0.06BaTiO3(NBT-BT:Er3+/Yb3+) cera-mics were synthesized by a traditional solid state reaction method. The XRD patterns show that all the ceramics are the single phase with perovskite structure. Under the excitation of 980 nm laser diode, the samples exhibit bright green up-conversion (UC) emission bands, which corresponds to the radiative transitions from (4S3/2,2H11/2) to4I15/2, respectively. By tailoring the ratio of Er3+/Yb3+, the optimal UC emission properties were obtained in NBT-BT:0.01Er, 0.10Yb ceramics. The thermal behavior of UC emission in the ceramics was also investigated and the maximum sensitivity based on fluorescence intensity ratio (FIR) technology was approximately 0.0040K−1at 502K. Moreover, ferroelectric and dielectric properties were enhanced with small amount of Er3+/Yb3+co-doped. These ceramics, with excellent properties, may be a potential candidate in the application for electro-optical devices. [ABSTRACT FROM AUTHOR]

Oxynitrides have been explored extensively in the past decade because of their interesting properties, such as visible-light absorption, photocatalytic activity and high dielectric permittivity. Their synthesis typically requires high-temperature NH3 treatment (800-1,300 °C) of precursors, such as oxides, but the highly reducing conditions and the low mobility of N3− species in the lattice place significant constraints on the composition and structure-and hence the properties-of the resulting oxynitrides. Here we show a topochemical route that enables the preparation of an oxynitride at low temperatures (<500 °C), using a perovskite oxyhydride as a host. The lability of H− in BaTiO3−xHx (x ≤ 0.6) allows H−/N3− exchange to occur, and yields a room-temperature ferroelectric BaTiO3−xN2x/3. This anion exchange is accompanied by a metal-to-insulator crossover via mixed O-H-N intermediates. These findings suggest that this 'labile hydride' strategy can be used to explore various oxynitrides, and perhaps other mixed anionic compounds. [ABSTRACT FROM AUTHOR]

Barium titanate (BaTiO 3 ) powder was prepared from the liquid phase precursor reaction of barium acetate with different types of Ti raw materials. Powders were synthesized using barium titanate, lactate A, lactate B, and TiCl 3 fired at 600, 800, 900, and 1000 °C. The effects of the addition of titanium raw materials on the nanostructure and synthesis efficiency were investigated in this work to develop nano-sized particles at a low firing temperature. BaTiO 3 nanopowders with different size distributions were synthesized using a liquid phase precursor with a titanium lactate complex as the Ti source at a low temperature. Also, the morphology and size of BaTiO 3 nanopowders were controlled by adjusting the barium and titanium precursor concentration and the type of titanium raw materials. The X-ray diffraction of powders calcined at different temperatures and compositions was undertaken. The average size of the nanopowders was identified using a scanning electron microscope which varied from ~25 nm to ~50 nm. [ABSTRACT FROM AUTHOR]

Oxynitrides have been explored extensively in the past decade because of their interesting properties, such as visible-light absorption, photocatalytic activity and high dielectric permittivity. Their synthesis typically requires high-temperature NH3 treatment (800-1,300 °C) of precursors, such as oxides, but the highly reducing conditions and the low mobility of N3− species in the lattice place significant constraints on the composition and structure-and hence the properties-of the resulting oxynitrides. Here we show a topochemical route that enables the preparation of an oxynitride at low temperatures (<500 °C), using a perovskite oxyhydride as a host. The lability of H− in BaTiO3−xHx (x ≤ 0.6) allows H−/N3− exchange to occur, and yields a room-temperature ferroelectric BaTiO3−xN2x/3. This anion exchange is accompanied by a metal-to-insulator crossover via mixed O-H-N intermediates. These findings suggest that this 'labile hydride' strategy can be used to explore various oxynitrides, and perhaps other mixed anionic compounds. [ABSTRACT FROM AUTHOR]

BaTiO 3 doped with various percentages of Co (1–5 mol%) was synthesized using a combined sol-gel-hydrothermal method. The structural characteristics of the compounds were investigated using X-ray diffraction and Raman spectroscopy. Surface chemical information and oxidation states were studied using X-ray photoelectron spectroscopy. The magnetic properties of the samples were studied using magnetization curves. In addition, quantum chemical calculations were performed to elucidate the electronic structure of the samples and to understand the possible substitution mechanisms during Co-doping. The results indicated that Co effectively endowed the BaTiO 3 structure with intrinsic magnetic properties, which decreased as the Co percentage increased. In addition, the increase in the Co mol% produced a gradual loss of the non-perovskite structure, leading to a decrease in the ferroelectric behaviour. [ABSTRACT FROM AUTHOR]

The synthesis of BaTiO 3 –MgFe 2 O 4 composite powders by a Pechini-like one-pot process and resulting ceramic bodies is described herein. Phase formation during the decomposition of homogenous (Ba, Ti, Fe, Mg)-gels was monitored up to 1200 °C. Composite powders consisting of BaTiO 3 and MgFe 2 O 4 were obtained after decomposition at 700 °C for 1 h resulting in crystallite sizes of about 10 nm. The shrinkage and sintering behaviour of compacted powders were examined. Sintering at ⩾1200 °C leads to the formation of hexagonal BaTiO 3 only for composites with a MgFe 2 O 4 content of ⩾30 wt.%. SEM images of ceramic bodies reveal that the MgFe 2 O 4 particles are surrounded by BaTiO 3 crystallites. Magnetic measurements of both powders and corresponding ceramic bodies show ferrimagnetic behaviour with low coercivities. At high-field and low temperatures an additional small paramagnetic contribution was observed which increases with decreasing MgFe 2 O 4 content and should be considered by the calculation of the saturation magnetization. Finally, the frequency dependent variation of the relative permittivities of the composites was investigated. [ABSTRACT FROM AUTHOR]