BaTiO3 Nanostructures Research Articles

Morphology-controlled BaTiO3 nanostructures with high sensitivity and fast response for respiratory monitoring

As a typical perovskite oxide, BaTiO3 has been fully proved to be an excellent impedance humidity sensing material, meanwhile its application in human respiratory monitoring needs to be further researched. In this contribution, BaTiO3 nanorods (BT-NR), nanowires (BT-NW) and micron particle (BT-MP) were successfully synthesized by the molten salt synthesis (MSS) method. Various characterization techniques were used to analyze the structure, morphology and composition of these materials. As-synthesized BaTiO3 samples had been assembled as impedimetric humidity sensors and then tested systematically under relatively humidity (RH) range of 11%–97%. All the three sensors exhibited high response values greater than three orders of magnitude, which are much higher than the commercial BaTiO3 (BT-C) sensor (S97% = 4.90 × 102). Thereinto, the BT-NR humidity sensor holds the fastest response-recovery times (1 s and 22 s) and the smallest hysteresis (ΔH = 0.67%). Excellent sensing performance of BT-NR can be attributed to synergistic effects of larger specific surface area and smaller pore size. In addition, the BT-NR humidity sensor shows considerable potential in the field of human respiratory monitoring. This work provides a new perspective to high-performance humidity sensors for human body-related detection through morphology-controlled perovskite nanostructures.

Synchrotron based x-ray absorption spectroscopy investigation and temperature dependent ferroelectric properties of Ni doped BaTiO3 nanostructures

In this report, the local structure geometry of BaTi1-xNixO3 (0.0 ≤ x ≤ 0.06) ceramics has been studied through synchrotron based x-ray-absorption spectroscopy, measured at the Ti K, Ba L3 and Ni K-edges at room temperature. The x-ray absorption near edge spectroscopy (XANES) at Ti K-edge confirms the TiO6 octahedron geometry of Ti atom due hybridization between Ti(3d)-O(2p) orbitals and signifies the non-centrosymmetric nature of BaTiO3 samples. However, Ti–O off-center displacement (non-centrosymmetric) is disturbed under the effect of Ni doping as a result of oxygen vacancies formation. More interestingly, XANES studies at Ni K-edge ensure successful substitution of Ni in BaTiO3 as Ni2+ ions. Extended x-ray absorption fine structure (EXAFS) data at Ni K-edge have been fitted to estimate pertinent local structural parameters of the Ni–O, Ni–Ba, Ni–Ti and Ni–Ni shells (viz. bond lengths and disorder parameters) and it also reveal that the structural disorders around the Ti sites in the doped BaTiO3 expand with Ni doping. The mixed-valence states of titanium ion, i.e., Ti4+ and Ti3+ in the doped samples were established with the x-ray photoelectron spectroscopy (XPS). Moreover, XPS divulges the creation of oxygen vacancies due to Ni doping in BaTiO3 matrix. The complementary information about the lattice vibration is analyzed through Raman studies that approve the softening of the transverse optical (TO) mode present at 515 cm−1. The temperature dependent ferroelectric studies affirm that the ferroelectricity vanishes in the doped samples due to the decrement in the off-center displacement between the Ti4+ and O2− ions in the TiO6 octahedral geometry. Differential thermal analysis (DTA) exhibits a ferroelectric tetragonal to para-electric cubic phase transition in the pristine as well as Ni doped BaTiO3 samples.

Doping‐induced diffused phase transition triggers gas‐sensing performance of Sn‐doped BaTiO3 nanostructures

The formation of polar nanoregions with a smaller doping concentration of Sn into BaTiO3 nanostructures governs significantly better gas‐sensing response for a NO2 gas at room temperature. Appropriate Sn doping in BaTiO3 nanostructures not only modifies the electronic structure but is also responsible for diffused phase transition in its crystal structure. Here, in this study, we performed high‐resolution transmission electron microscopy of the Sn‐doped BaTiO3 samples to observe the formed polar nanoregions; 0.2 M% Sn‐doped BaTiO3 possesses a higher polarization value at room temperature to adsorb NO2 gas on the surface of the thick film resistor‐based gas sensor, improving its gas‐sensing performance. The electronic structure and density of states of pristine and Sn‐doped BaTiO3 were studied by density functional theory calculations, and the results of the same revealed improved gas‐sensing performance in the case of Sn‐doped BaTiO3 nanostructures.

Sensing capabilities of ultrathin BaTiO3 nanostructures toward carbon oxides based on optical signals from the theoretical perspective

Due to the large presence of carbon oxide gases in both our environment and industry, there is an ongoing search for simple and efficient gas sensors. As a response to the current challenges toward lower limits of detection, in this work we propose a detection of optical signals from ultrathin BaTiO3 nanostructures as the basis for carbon oxides sensing. Based on density functional theory, we simulate the sensitivity of electrical and optical properties of the ultrathin BaTiO3 nanostructure with respect to different adsorption sites on the (001)-BaTiO3 surface. Significant changes in the optical activity, including absorption, reflection and EELS spectra, are detected. Supercell model study showed that optical signals follow a monotonous trend with respect to the molecule concentration. The changes are explained via charge transfer between the (001)-BaTiO3 surface and the adsorbed gas molecules. An insight into the physical and chemical nature of the processes at the nano-scale improves our understanding of the sensing mechanism. At the same time, the obtained results might pave a way to new easy-to-use but robust sensor designs.

Barium Titanate Nanostructures and Thin Films for Photonics

AbstractBarium titanate (BaTiO3) is a synthetic crystal used in electromechanical transducers and multilayer ceramic capacitors. Since it is not available in nature, a variety of growth methods has been employed to produce in large scale, with high quality and low‐cost. BaTiO3, as a metal oxide meets practical requirements such as physical hardness, stability and tunable optoelectronic properties. The plethora of characteristics renders it functional in diverse fields of applications from energy harvesting to biophotonics. Related to optical properties, it is a dielectric material from the near ultraviolet to the near‐infrared part of the spectrum with low optical losses and relatively high refractive index. The strong second‐order nonlinear response has resulted in several breakthroughs in bioimaging, while its intrinsic electrooptic response is among the highest within the existing materials. The properties of the BaTiO3 may also be modified by doping or hybridization with other materials. This review presents the basic optoelectronic properties of BaTiO3, reports on the recent advances in BaTiO3 nanostructures and thin films related to photonic applications, and oversees photonic technologies that may benefit from this material platform in the near future.

Synthesis and comprehensive study of polyvinylidene fluoride–nickel oxide–barium titanate (PVDF–NiO–BaTiO3) hybrid nanocomposite films for enhancement of the electroactive beta phase

This study includes the successful fabrication of polyvinylidene fluoride (PVDF) based hybrid nanocomposite films loaded with nickel oxide (NiO) and barium titanate (BaTiO3) fillers via simple sol–gel casting techniques to optimize the crystallinity and β-phase formation for various sensor applications. A systematic study has been performed to assess the effect of fillers (NiO and BaTiO3) on the crystal structure, morphology and electrical conduction properties of PVDF–NiO–BaTiO3 hybrid nanocomposite films using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FESEM) using energy dispersive spectroscopy and current–voltage (I–V) measurement techniques. XRD and FTIR results indicate that the incorporation of nanostructured fillers NiO and BaTiO3 leads to the formation of long stabilized planar zigzag and all-trans conformation (TTTT) inducing the growth of electroactive β-phase and crystallinity. XRD results show that the degree of crystallinity reaches a maximum value of 85% for incorporation of 2.5 wt% of NiO and 27.5 wt% of BaTiO3. FTIR results show 85% of electroactive β-phase growth achieved by incorporating 7.5 wt% of NiO and 22.5 wt% of BaTiO3. FESEM micrographs of hybrid films show that both NiO and BaTiO3 particles are well dispersed within the PVDF pattern with the porous surface resulting in enhanced electrical conductivity. Current–voltage (I–V) measurement shows the charge transport process in PVDF composites loaded with NiO and BaTiO3 fillers is mainly governed by Richardson Schottky emission. The significant increase in the electrical conductivity of PVDF–NiO–BaTiO3 hybrid nanocomposite opens a new window for possible use in miniaturization of electronics and energy harvesting devices.

Synthesizing BaTiO3 Nanostructures to Explore Morphological Influence, Kinetics, and Mechanism of Piezocatalytic Dye Degradation.

Piezocatalysts have attracted much attention due to their excellent degradation ability for organics. In this work, three types of BaTiO3 (BTO) nanostructures, including hydrothermally synthesized nanocubes (NCs), sol-gel calcined nanoparticles (NPs), and electrospun nanofibers (NFs), are prepared for catalyzing the dye degradation. Compared with the NCs and NPs, the NFs exhibit a higher piezocatalytic degradation performance due to the large specific surface area, fine crystal size, and easy deformation structure. Moreover, the kinetic factors, including initial dye concentration, ionic strength, ultrasonic power, and applied action, influencing the degradation performance of the BTO NFs are analyzed deeply. A high degradation rate constant of 0.0736 min-1 is achieved for rhodamine B, which is superior compared with the previous reports. The excellent stability of BTO NFs is demonstrated by the cycling tests, where a high degradation efficiency of 97.6% within 110 min is still obtained after the third cycle. Furthermore, the mechanism of piezocatalysis revealed that the hydroxyl and superoxide radicals are the main reactive species in the degradation process. This work is of importance for the development of high-performance piezocatalysts and highlights the potential of piezocatalysis for water remediation.

BaTiO3 Nanosheets and Caps Grown on TiO2 Nanorod Arrays as Thin-Film Catalysts for Piezocatalytic Applications.

Powder-form piezocatalysts suffer from poor recyclability and pose a potential threat of creating serious secondary pollution, which restrict their practical applications. Thin-film piezocatalysts, which not only exhibit good recyclability but also fully contact with solution, are believed to be one of the solutions to address these problems. In this work, the nanostructured BaTiO3 (BTO) thin films were fabricated by a facile hydrothermal method for their potential applications in piezocatalysis. The vertically standing BTO nanosheets grown on the top of TiO2 nanorod arrays exhibited superior piezocatalytic performance as well as piezo-electrochemical property. Given the different strain states between thin-film piezocatalyst and powder-form piezocatalyst, both the impact force of water and isostatic pressure are taken into consideration in finite element method (FEM) simulation. The FEM simulation shows that a stronger piezoelectric filed can be built in BTO nanosheets because of their easier deformation, and thus can lead to a higher piezocatalytic degradation efficiency. Our work presented here is expected to provide a potential route for the nanoengineering of thin-film piezocatalysts and clarify the catalytic mechanism for substrate-fixed piezocatalysts.

Optimization of strontium- doping concentration in BaTiO3 nanostructures for room temperature NH3 and NO2 gas sensing

In this study, we comprehensively present the gas sensing performance of strontium (Sr)-doped barium titanate (BaTiO3) nanostructures which are synthesized by a low-temperature hydrothermal route. The in-situ doping of strontium in BaTiO3 nanostructures is achieved with different molar concentrations of Sr, and the sensing performance was evaluated by screen printing process of products to form their thick films. The thick films of as-prepared Sr-doped BaTiO3 (BaSrTiO3) were investigated for gas sensing performance for various gases at different operating temperatures where strong response was observed for both nitrogen dioxide (NO2) and ammonia (NH3) gases at room temperature. Furthermore, the sensing response at room temperature for NH3 and NO2 gases was also studied with respect to Sr doping concentrations in BaTiO3 nanostructures.

Novel fractal analysis of nanograin growth in BaTiO3 thin film

The grain size and the ferroelectric morphology are the two most important factors in the research and development of advanced dielectric devices. It is important to synthesize nanostructures in order to achieve optimal grain size and inhibit grain growth while controlling the sintering parameters. It is also important to find new methods to study the grain growth during densification. BaTiO3 films were successfully obtained via the sol-gel spin coating method.In this paper, we report the deposition of nanostructured BaTiO3 thin film by spin coating of sol-gel precursors. The densification, grain growth and microstructure evolution have been studied. Moreover, a novel physical and mathematical fractal analysis have been applied successfully to the densification and nano grain growth of BaTiO3 thin film. The discrepancy between the fractal dimension and the grain growth with increasing temperatures and soaking time are presented and discussed.

Synthesis and SPEF-Induced Enhanced Photoelectrochemical Performance of the BaTiO3@α-Fe2O3 Ferroelectric Heterojunction

We have combined ferroelectric BaTiO3 nanostructures with α-Fe2O3 nanoparticles to prepare BaTiO3@α-Fe2O3 core@shell heterojunction photoelectrodes. The effects of α-Fe2O3 nanoparticle loadings on ...

Influence of thermal treatment on dielectric and magnetic properties of nanocrystalline BaTiO3

Influence of thermal treatment on magnetic and dielectric properties of nanostructured BaTiO3 samples, sintered at 700, 1000 and 1200 °C was studied. The sample sintered at 700 °C is not ferroelectric one, and then two other samples undergo a ferroelectric phase transition at ≈ 393 K. It was found that all samples after aging at room temperature during the month after preparation demonstrated the diamagnetic response. Annealing at 250–350 °C leads to the increase in ferromagnetic magnetization and diamagnetic response. The both superparamagnetic magnetization and diamagnetic response are decreased with a rise of the sintering temperature.

La doped BaTiO3 nanostructures for room temperature sensing of NO2/NH3: Focus on La concentration and sensing mechanism

Among all the metal oxide based sensing materials, Barium titanate (BaTiO3) is captivating attention due to its strong ferromagnetic and dielectric properties. Continuing the interest, we present gas sensing properties of Lanthanum (La) doped BaTiO3 nanostructures. For this purpose, we demonstrate the in-situ doping of BaTiO3 nanostructures with varied molar concentrations of La and then reveal its effect on their gas-sensing mechanism. The as-prepared La doped BaTiO3 (BaLaTiO3) nanostructures were used as thick films for sensing performance against various interfering gases at operating temperature from RT to 450 °C. The thick films of La doped BaTiO3 nanostructures showed strong response for both NO2 and NH3 gases at room temperature. The effect of doping on the mechanism of gas sensing, selectivity and stability of the sensing devices are discussed.

Multiscale measurements of piezoelectric response of hydrothermal converted BaTiO3 1D vertical arrays

In this work, the piezoelectric properties of BaTiO3 1D vertical nanostructures were investigated with a comparison between the macroscopic and the nanometric response. The piezoelectric nanostructured carpet was obtained by the topotactic conversion of anodic TiO2 nanotubes exploiting hydrothermal treatment in Ba-enriched water solution. The nanoscale investigation by a piezoelectric force microscope returns a detailed map of ferroelectric polarization, which is preferentially confined over the vertical nanostructure axis. The scanning probe microscopy results were then coupled to the macroscopic response of the piezo-evaluation system to compare the multiscale response of the nanostructured material. Both the local and macroscopic measurement techniques provide d33 values in the range of 5.5–7 pm/V, in agreement with the values reported in the literature for other barium titanate nanostructures. The characterization of the piezoelectric response of BaTiO3 nanostructures at the nanoscale can provide useful guidelines for the next generation of Pb-free materials to be integrated into near-future nanodevices.

Er-Doped Nanostructured BaTiO₃ for NIR to Visible Upconversion.

Photoluminescent mechanisms in erbium-doped barium titanate nanoparticle systems were studied. Er3+ ions were introduced into the BaTiO3 lattice by the sol-gel method. The resulting Er3+ concentration was between 0% and 5%, with Ba/Ti ratios of 1.008 and 0.993. The stoichiometry of Ba and Ti concentrations in the lattice influenced the doping mechanism and placement of erbium ions in the lattice structure. Our research shows the existence of a strong correlation between Ba/Ti ratios, erbium concentration, phase structure and doping site location on the upconversion photoluminescence mechanisms. Competing upconversion emissions 2H11/2/4S3/2→4I15/2 at 523 and 548 nm respectively and other photoluminescent mechanisms as 4I9/2→4I11/2 around 4000 nm (2500 cm−1) were studied using Raman and emission spectroscopy. The upconversion process is predominant over other photoluminescent decay when the material presents high distortion in the surrounding activator.

Chemical Synthesis of Multilayered Nanostructured Perovskite Thin Films with Dielectric Features for Electric Capacitors

We report a simple sol–gel method for the preparation of multilayered hybrid thin films composed of nanostructured SrTiO3 (STO) and BaTiO3 (BTO) layers. A nanoporous thin film of STO is prepared by the spin-coating method on Si/SiO2/Ti/Pt substrate. When the BTO is processed, the BTO is crystallized between STO crystal pores. A significant strain field is induced on the interface between the STO and BTO surfaces. The concave shape of the nanopores could enable the realization of a highly strained interfacial heterostructure composed of STO/BTO. Compared to nanostructured STO, BTO, and bilayer STO/BTO films, multilayered STO/BTO films show the highest dielectric constant and a high Curie temperature (Tc) at around 280 °C, which is suitable for electric capacitor applications.

Self-powered wire type UV sensor using in-situ radial growth of BaTiO3 and TiO2 nanostructures on human hair sized single Ti-wire

A flexible, non-planar, human hair sized [Diameter (Ø) ≈100 μm, Length (L) ≤6 cm] Ti-wire/BaTiO3 (BTO) core-shell nanostructures (NSs) was developed using chemical oxidation-modification (COM) method followed by a low-temperature hydrothermal technique. COM method of flexible/non-flexible Ti-wires (Ø ≈ 800 μm, 100 μm) outer surface generates uniform distribution/continuous radial growth of TiO2 nanoneedles/nanoparticles having anatase crystalline phase. Photo-responsive performance investigated by fabricating the TiO2 NSs/Ti wire (TW) based UV sensors as a function of fixed bias voltages (±1 V and ±7 V) under various light sources having wavelengths (λ) 365 nm, 405 nm and 535 nm. TW-UV sensor (Ø ≈ 800 μm) has higher photo-responsivity ≈35.024 μA/W than the TW-UV sensor (Ø ≈ 100 μm) under the light intensity ≈18 mW/cm2 (λ ≈ 365 nm) at bias voltage ≈−1 V, respectively. Further, the XPS spectra of the tetragonal crystalline phase of radially grown BTO NSs confirms the presence of Ba 2+ and Ti +4 oxidation states directly connected to the internal stresses of TiO6 octahedron in BTO lattice. Next, flexible wire based piezoelectric nanogenerator (FW-PNG) was fabricated to harness the mechanical energy, biomechanical motions into useful electrical energy. Realized self-powered UV sensor by the parallel connection between FW-PNG and TW-UV sensor as a function of constant mechanical load (2 N) under various light intensities (18, 40 and 60 mW/cm2) of source wavelength 365 nm, respectively. This study can pave the way for developing micro/nanodevices on non-planar mechanical structures; human hair sized energy harvesters and self-powered sensors.

Synthesis and growth studies of barium titanates: 0−D and 1−D nanostructures using hydrogen titanate precursor

The present work demonstrates a simple and efficient route to synthesize a variety of barium titanate (BaTiO3) nanostructures including nanowires, nanoswords, nanostars, nanocubes, and nanoparticles by a facile hydrothermal approach. The experiments showed that different morphologies can easily be tuned by varying the concentration of precursors, i.e., hydrogen titanate (H2Ti3O7) and barium hydroxide octahydrate (Ba(OH)2.8H2O), while keeping the molar ratio, reaction temperature and time fixed. The structure and morphology of BaTiO3 were characterized by field emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD). The results indicate that BaTiO3 nanowires are in cubic phase with an average diameter of 80-100 nm. The shape of BaTiO3 changes from nanowires to nanoparticles with an increase in Ba(OH)2.8H2O concentration from 0.08 M to 0.51 M. Two possible mechanisms, in-situ topotactic transformation reaction and dissolution-deposition reaction have been suggested for different morphologies of BaTiO3. The synthesized 0-D and 1-D BaTiO3 nanostructures are promising materials for many applications because of their excellent dielectric, ferroelectric and piezoelectric properties. The present work will open a new route to single reaction parameter dependent synthesis of 0- and 1-D BaTiO3 nanostructures which can find a range of applications including electronics, catalysis, energy harvesting, etc.

BaTiO3 nanostructures for H2S gas sensor: Influence of band-gap, size and shape on sensing mechanism

We present a low temperature hydrothermal route for synthesis of Barium titanate (BaTiO3) nanostructures for their utility in H2S gas sensing. We established the reaction parameters to obtain sub-100 nm BaTiO3 nanostructures (spherical, hexagonal and rods) and subjected them form a thick film by screen-printing technique. These calcined thick films were exposed to various gases at different working temperature for sensing studies. The as-fabricated thick film of BaTiO3 selectively sensed H2S gas at a working temperature range from 200 to 300 °C. The role of Desulphurization band-gap, size and shape of BaTiO3 nanostructures in H2S gas sensing mechanism is discussed in detail.

Extrinsic contributions to the dielectric response in sintered BaTiO3 nanostructures in paraelectric and ferroelectric regimes

Post sintering studies of BaTiO3 (BTO) nanoparticles are presented in detail. Bulk nanostructures were prepared via three different compaction processes, namely, uniaxial cold pressing (UCP), Cold Isostatic Pressing (CIP) and Spark Plasma Sintering (SPS). Effect of compaction technique on microstructures have been investigated and correlated with electrical response for each sample. In addition to the transport properties, temperature and frequency dependent dielectric response of variously sintered samples and bulk counterpart was recorded. Several aspects have been identified that are essential to be taken into account in order to completely understand physical processes. Drastically distinct features were observed in paraelectric (PE) regime well above ferroelectric (FE)-PE transition temperature. These features include intra grain conduction with a reduction in the magnitude of PE to FE peak dielectric constant magnitude. Role of strain, grain boundary conduction associated with observation of Maxwell Wagner relaxation and hopping conduction in dielectric and ferroelectric response have been observed and discussed. Densification with presence of oxygen vacancies, significantly enhances conductivity associated with the hopping of the carriers, in turn deteriorated ferroelectric response.