Photocatalytic,piezocatalytic, and piezo-photocatalytic effects in ferroelectric (Ba0.875Ca0.125)(Ti0.95Sn0.05)O3 ceramics

Ba_0.875Ca_0.125Ti_0.95Sn_0.05O₃ (BCT-Sn) was examined for photocatalytic, piezocatalytic, and piezo-photocatalytic effects. BCT-Sn powder was poled through corona poling and it was found that poling induces significant impact on photocatalysis. This material was also able to degrade dye (Methylene blue) using poled powder under ultrasonication (piezocatalysis). There was a remarkable effect in dye degradation which is a clear indication of the importance of piezocatalytic behavior in catalytic reactions. Moreover, the piezo-photocatalytic effect (piezocatalysis + photocatalysis) was also investigated. Results suggested an enormous scope of ferroelectric materials in the field of catalysis.     

Dye degradation and bacterial disinfection using multicatalytic BaZr0.02Ti0.98O3 ceramics

The piezocatalytic, photocatalytic, and piezo-photocatalytic properties of BaZr_0.02Ti_0.98O₃ (BZT) were examined for degradation of organic dyes and killing of bacteria present in the wastewater. Poled and unpoled powder samples were investigated using rhodamine-B (RB), methyl orange (MO) dyes, and gram-negative Escherichia coli in simulated water. The poled BZT sample demonstrated significant degradation of RB and MO dyes as compared to the unpoled BZT sample during piezocatalytic, photocatalytic, and piezo-photocatalytic experiments. Moreover, ultrasonication-induced piezocatalysis was found to be more effective than stirring in dye degradation using the poled BZT sample. Also, the piezo-photocatalysis through poled BZT sample (using ultrasonication and ultraviolet (UV) light) was found to be more effective in dye degradation than that of only piezocatalysis and only photocatalysis. During antibacterial testing, the poled BZT sample showed nearly 90% and 100% bacterial killing under UV light and ultrasonication, respectively,, whereas the unpoled BZT sample showed only ~5% and ~35% bacterial killing. The significant enhancement in dye degradation and bacterial killing using the poled sample explicitly indicated the role of internal electric field in multicatalytic activities.     

Effect of ferroelectric polarization on piezo/photocatalysis in Ag nanoparticles loaded 0.5(Ba0.7Ca0.3)TiO3–0.5Ba(Zr0.1Ti0.9)O3 composites towards the degradation of organic pollutants

A 0.5(Ba_0.7Ca_0.3)TiO₃–0.5Ba(Zr_0.1Ti_0.9)O₃ (BCT-BZT) ceramic was studied for photocatalysis and piezocatalysis effects using dye degradation (methylene blue, rhodamine B, and methyl orange) and bacterial (Escherichia coli) disinfection from aqueous solution. To examine the effect of ferroelectric polarization, BCT-BZT powder was poled using the corona poling technique. Same time, BCT-BZT was converted into Ag/BCT-BZT composites as Ag induced surface plasmon resonance effect during photocatalysis. Piezocatalysis performance was assessed for dyes mineralization under ultrasonication. There was a significant impact of silver nanoparticles on the photo/piezocatalysis performance of BCT-BZT. Similarly, electric poling has also played a positive role in improving the photo/piezocatalysis in view of various dye degradation. These samples also showed effective antibacterial performance.     

Solar/visible light photocatalytic dye degradation using BaTi1−xFexO3 ceramics

BaTi_1−xFe_xO₃ compositions (for x = 0, 0.1, and 0.2) were prepared via a solid-state reaction route. The presence of iron (Fe) in barium titanate (BaTiO₃) eventually decreased the energy bandgap; thus, its utilization for water cleaning application through photocatalysis process was explored (using methylene blue [MB] dye as an indicative pollutant in water). Characterization of the synthesized powder was performed through scanning electron microscopy, X-ray diffraction, Raman spectroscopy, and X-ray photoelectron spectroscopy. The bandgap of the synthesized powder was calculated as 3.2, 2.12, and 1.67 eV for BaTi_1−xFe_xO₃ compositions (for x = 0, 0.1, and 0.2), respectively. BaTi_0.8Fe_0.2O₃ powder showed excellent results, and ∼71% of the MB dye (∼5 mg/L concentrated) was degraded using the photocatalysis process under visible light. To check the potentiality of BaTi_1−xFe_xO₃ compositions (for x = 0, 0.1, and 0.2), the photocatalysis process was carried out by changing the concentration of MB dye (2.5–10 mg/L with a step of 2.5 mg/L) and the amount of BaTi_0.8Fe_0.2O₃ powder (0.05–0.2 g with a step of 0.05 g) for ∼5-mg/L concentrated MB dye. The treated water was further used as a growth parameter and phytotoxicity analysis through germination index on the wheat seeds. Lastly, the BaTi_1−xFe_xO₃ compositions (for x = 0, 0.1, and 0.2) were explored for water cleaning applications under real-time solar irradiation.     

Piezo-photocatalytic activity of mechanochemically synthesized BiVO4 for dye cleaning

Single-phase BiVO₄ (BV) powder was synthesized successfully at 600°C within 4 h duration through the mechanochemical high energy ball milling method, and the combined photocatalytic and piezocatalytic activity was studied to exhibit piezo-photocatalytic efficiency. Monoclinic BV phase existence in the synthesized powder was affirmed through Raman spectroscopy and the X-ray diffraction techniques. The scanning electron microscopy affirmed the irregular-shaped BV powder in the synthesized powders. X-ray photoelectron spectroscopy affirmed the existence of various oxidation states of the elements V, Bi, and O in BV powders. The piezocatalytic and photocatalytic methylene blue (MB) dye degradation efficiency using BV powdered sample was observed to be 28% and 60%, respectively, within 240 min. The piezo-photocatalytic MB dye degradation using BV powdered sample was observed to be 81% within 240 min. Effect of dye concentration on kinetic rate constant was also studied.     

Surface plasmon resonance-induced Ag-BaTiO3 composites for catalytic performance

Ferroelectric BaTiO₃ was combined with Ag nanoparticles for piezocatalytic and photocatalytic viewpoints. Microstructural characterization (X-ray diffraction and electron microscopy images) revealed that the Ag was successfully bounded with BaTiO₃. X-ray photoelectron spectrum also confirmed the presence of Ag. Further, its performance was examined for dye degradation under visible light (for photocatalysis) and ultrasonication (for piezocatalysis). In both the catalysis processes, there was a significant improvement in Ag-loaded BaTiO₃ sample-based catalytic reactions. Catalytic performance was evaluated for multiple cycles and was found consistent. Scavenger tests were also performed to understand catalytic reactions.     

Utilizing the localized surface piezoelectricity of centrosymmetric Sr1-xFexTiO3 (x≤0.2) ceramics for piezocatalytic dye degradation

Centrosymmetric Sr_1-xFe_xTiO₃ (x = 0, 0.01, 0.05, 0.1, 0.2) ceramics were synthesized using solid-state reaction method. XRD confirmed the perovskite SrTiO₃ phase in all samples and indicated the conversion of cubic to pseudocubic crystal symmetry with increase in Fe substitution. Raman spectroscopy showed first and second order Raman scattering modes in all samples and a new Raman mode in 691–701 cm^-1 in Fe substituted samples. The irregular morphology of grains in Sr_1-xFe_xTiO₃ (x≤0.1) was interestingly transformed into rhombicuboctahedron morphology in x = 0.2 sample. All samples showed significant piezocatalytic degradation of methylene blue (MB) dye. The piezocatalytic dye degradation was increased with increase in Fe substitution. The best piezocatalytic dye degradation rate of 0.00448 min^-1 was achieved in x = 0.2 sample. The localized surface piezoelectricity along with some other sono-induced phenomena might be responsible for piezocatalytic activity. The sample with x = 0.2 also showed promising MB dye degradation under visible light (k = 0.00364 min^-1).     

Antibacterial and photocatalytic active transparent TiO2 crystallized CaO–BaO–B2O3–Al2O3–TiO2–ZnO glass nanocomposites

Transparent TiO₂ crystallized 5CaO–10BaO–65B₂O₃–Al₂O₃–20TiO₂–10ZnO (CBBATZ) glass nanocomposites were fabricated using melt-quenching technique followed by specific heat treatments. As-quenched glass samples were provided three different heat treatments at 630°C for 3, 5, and 10 hours in order to obtain different amounts of TiO₂ nanocrystals in the glass. The presence of rutile phase of TiO₂ nanocrystals in glass was confirmed by X-ray diffraction. The glass nanocomposite heat treated for 10 hours showed a hydrophobic nature with contact angle of 90.90°. Contact angle decreased from 90.90 to 22.20°, when irradiated under ultraviolet (UV) radiation for 45 minutes. This photoinduced hydrophilicity showed a photocatalytic and self-cleaning properties of glass nanocomposite. During photocatalytic ink test, the maximum change in color of Resurin (Rz) ink and 60% degradation in absorbance of ink within 150 minutes under UV radiation were found for glass nanocomposite heat treated at 10 hours. Also, 78% degradation in absorbance of methylene blue dye (pollutant) within 180 minutes under UV irradiation was found for glass naocomposite heat-treated at 10 hours. Antibacterial performance of transparent glass nanocomposite against Escherichia coli was evaluated as well. More than 95% of the bacterial cells were degraded with glass nanocomposite heat-treated at 10 hours. CBBATZ glass nanocomposite found to impart the antibacterial effect through generation of reactive oxygen species (ROS) in aqueous medium. ROS species which was confirmed in the bacterial cell through intracellular ROS generation kit. During evaluation of mechanical properties using nanoindentation technique, the values of hardness and reduced modulus increased by ~26% and 10%, respectively, for glass nanocomposite heat-treated at 10 hours as compared to as-quenched glass.     

Hydrothermal synthesis of pseudocubic BaTiO3 nanoparticles using TiO2 nanofibers: Study on photocatalytic and dielectric properties

In this study, TiO₂ nanofibers were fabricated via the electrospinning method followed by air annealing. Then, Ti-requirement in the conventional hydrothermal synthesis of BaTiO₃ stoichiometry was supplied by using these nanofibers. The microstructural and compositional properties of BaTiO₃ nanoparticles were studied using SEM, TEM, XRD, XPS, and Raman spectroscopy. The structural analysis showed that the cubic symmetry was the dominant one in the BaTiO₃ nanoparticles, whereas Raman spectroscopy indicated the coexistence of cubic symmetry with the tetragonal polymorph. The nanoparticles displayed higher photocatalytic reactivity under UV-A light compared to visible irradiation during decomposition of methylene blue dye and reached 24.2% and 18.8% degradation, respectively, after 1 hour. Furthermore, the dielectric properties were investigated using sintered compacts of these nanoparticles. Among the employed temperatures for sintering, the highest relative density (90%) and dielectric constant (2165 at 1 MHz) were obtained at 1250°C and 5 hours. This study revealed that the electrospun TiO₂ nanofiber precursor can successfully be used for the production of nanoscale barium titanate particles suitable for various applications.     

Influence of particle size on 3D-printed piezoelectric ceramics via digital light processing with furnace sintering

To improve the properties of BaTiO₃ piezoelectric ceramics fabricated by 3D printing, effects of particle size were investigated on the properties of ceramic slurries and the electrical properties of BaTiO₃ fabricated by Digital light processing (DLP) 3D printing method. It was found that the curing ability of the slurries decreased significantly when the particle size is close to the ultraviolet wavelength, while the viscosity kept decreasing with the increase of particle size. When the particle size in a range of submicron (d₅₀<1 μm), the grain size of sintered ceramics decreased from 13.27 to 6.84 μm as particle size increasing. Moreover, the piezoelectric constant and relative permittivity of sintered ceramics were measured, and it turns out to reach 168.1 pC/N and 1512, respectively, while using the BaTiO₃ powder with particle size of 993 nm. Finally, a cellular structural BaTiO₃ ceramics was fabricated by using optimized powder and process parameters and packaged as a piezoelectric sensor, showing a good function of force-electricity conversion. These results demonstrate the feasibility of fabricating high-quality functional ceramics with designed geometry by DLP.     

Enhanced magnetic,ferroelectric, and photocatalytic properties of (1-x)BiFeO3-xBaTiO3 (0.0 ≤ x ≤ 0.4) powders

The magnetic, ferroelectric, and photocatalytic properties of (1-x)BiFeO₃-xBaTiO₃ (0.0 ≤ x ≤ 0.4) powders synthesized by sol-gel method have been investigated. X-ray diffractometry confirms that the phase of the samples changed from rhombohedral to cubic with the increase in BaTiO₃ content. The grain size decreases and the particle shape becomes homogeneous with the introduction of BaTiO₃. BaTiO₃ substitution enhances the multiferroic properties of the ceramics and the maximum remnant magnetization (0.261 emu/g) and remnant polarization (20 μC/cm²) have acquired in 0.8BiFeO₃-0.2BaTiO₃ and 0.7BiFeO₃-0.3BaTiO₃, respectively. The absorbance in ultraviolet and visible light regions is improved obviously for powder with x = 0.3. The energy band gap of the samples decreases from 2.06 eV to 1.57 eV with the introduction of BaTiO₃, indicating that the excitation rate of photogenerated electron-hole pairs is improved. The highest methylene blue degradation efficiency of ~62% within 3 h under the visible light is achieved in the 0.7BiFeO₃-0.3BaTiO₃ which can be attributed to its suitable energy band gap and large remnant polarization.     

Flow Cytometry Analysis of Cytotoxicity In Vitro and Long‐Term Toxicity of HA‐40 wt% BaTiO3 Nanoparticles In Vivo

The development of new implantable biomaterials requires bone‐mimicking physical properties together with desired biocompatible property. In continuation to our earlier published research to establish compositional dependent multifunctional bone‐like properties and cytocompatibility response of hydroxyapatite (HA)‐BaTiO₃ composites, the toxicological property evaluation, both in vitro and in vivo, were conducted on HA‐40 wt% BaTiO₃ and reported in this work. In particular, this work reports in vitro cytotoxicity of mouse myoblast cells as well as in vivo long‐term tissue and nanoparticles interaction of intra‐articularly injected HA‐40 wt% BaTiO₃ and BaTiO₃ up to the concentration of 25 mg/mL in physiological saline over 12 weeks in mouse model. The careful analysis of flow cytometry results could not reveal any statistically significant difference in terms of early/late apoptotic cells or necrotic cells over 8 d in culture. Extensive histological analysis could not record any signature of cellular level toxicity or pronounced inflammatory response in vital organs as well as at knee joints of Balb/c mice after 12 weeks. Taken together, this study establishes nontoxic nature of HA‐40 wt% BaTiO₃ and therefore, HA‐40 wt% BaTiO₃ can be used safely for various biomedical applications.     

TiO2–BaTiO3 nanocomposite for electron capture in dye‐sensitized solar cells

Different compositions of TiO₂–BaTiO₃ nanocomposites are synthesized with various weight ratios for dye‐sensitized solar cell (DSSC) applications. TiO₂ and BaTiO₃ nanoparticles (NPs) are synthesized by sol‐gel and solvothermal methods, respectively and are employed as the photoanode electrodes. BaTiO₃ NPs have pure cubic perovskite crystal structure with an average size of 20‐40 nm, while TiO₂ NPs show pure anatase phase with 15‐30 nm size. The power conversion efficiency (PCE) enhancement of the cells is first attained by controlling the thickness of the films for light harvesting improvement. The fabricated DSSC composed of pure BaTiO₃ NPs with an optimal thickness of 25 μm shows efficiency of 6.83%, whereas that made of pure TiO₂ NPs with 14 μm thickness has cell efficiency of 7.24%. Further improvement of cell efficiency is achieved by preparation of binary oxide nanocomposites using TiO₂ and BaTiO₃ NPs with various weight ratios. The highest PCE of 9.40% is obtained for the nanocomposite with TiO₂:BaTiO₃=85:15 (wt%). The enhancement is assigned to less recombination of photo‐generated electrons and higher incident photon to current conversion yield as a result of rapid charge collection and higher dye sensitization.     

Ball milling–based piezocatalysis using .5Ba(Zr0.2Ti0.8)O3–.5(Ba0.7Sr0.3)TiO3 ceramics

One of the newly light on processes utilized in applications for cleaning water is piezocatalysis. Mechanical vibrations generated through ultrasonication are generally used to separate out the charges in ferroelectric ceramics. The current research presents a novel prospective methodology of ball milling, where it is used as a facile and green technique for water remediation. The movement of the planetary ball mill imparts enough force such that reactive species are produced which are responsible for organic dye degradation. One of the results in the parametric analysis showed that by using 0.30 g of the 0.5Ba(Zr_0.2Ti_0.8)O₃–0.5(Ba_0.7Sr_0.3)TiO₃ (BST–BZT) powder, 62% of the methylene blue (MB) dye was degraded in 60 minutes.     

Construction of CuS/ZnO Z-scheme heterojunction as highly efficient piezocatalyst for degradation of organic pollutant and promoting N2 fixation properties

Piezocatalytic technology has great potential in addressing water-system pollution and countering energy crises issues. Herein, high-performance CuS/ZnO Z-scheme heterojunction piezocatalyst was prepared by environmentally friendly solid-state chemistry approach and explored piezocatalytic performances toward degradation of organic methylene blue (MB) dye pollutant and nitrogen (N₂) fixation activity under ultrasonic vibration. The CuS/ZnO piezocatalyst presents outstanding property in MB degradation process with high efficiency (94.7% in 40 min), high rate constant (0.06804 min⁻¹) and good recyclability stability in comparison with the numerous ZnO-based piezocatalysts. In addition, this catalyst also exhibits superior piezocatalytic activity with a production rate of nitrogen fixation rate of 77.5 μmol L⁻¹ g_cat⁻¹ h⁻¹ in the reduction of N₂ to ammonia process, which is approximately 4-folds higher than that of pristine ZnO. Such improvement was mainly attributed to the facilitating charge carriers separation via rational construction of Z-scheme heterojunction as well as enhanced redox capacity. A novel piezocatalytic Z-scheme heterojunction mechanism of CuS/ZnO has been proposed and elucidated. This work suggests that designing highly efficient CuS/ZnO piezocatalyst will be a promising candidate material for prospects application in coping with the environmental remediation pollutants and energy crisis problems.     

Solvothermally synthesized tetragonal barium titanate powders using H2O/EtOH solvent

Multilayer ceramic capacitor (MLCC) miniaturization has increased the demand for superfine BaTiO₃ powder due to its thin dielectric layer. Hydrothermally synthesized BaTiO₃ powder has submicron size, high purity and good crystalline nature at low synthetic temperature. However, the powder has a pseudo-cubic phase resulting in poor dielectric properties due to size effect and hydroxyl ion inclusion in the BaTiO₃ lattice. We attempted a superfine (lower than 100 nm) highly tetragonal BaTiO₃ powder via a solvothermal method without precipitating agent. Solvent composition effects on the BaTiO₃ powder tetragonality were discussed.     

Sonocatalysis and Photocatalysis in Ba0.5Sr0.5TiO3 ceramics

The photocatalytic, sonocatalytic, and sono-photocatalytic performances of Ba_0.5Sr_0.5TiO₃ (BST) ceramic (synthesized through solid-state reaction route) were investigated for the degradation of an organic dye named methylene blue (MB). The as-prepared BST ceramic powder was characterized using a scanning electron microscope, X-ray diffraction, X-ray photoelectron, and Raman spectroscopy techniques. The optical energy band gap of BST ceramic was found to be ∼3.17 eV. BST has shown significant catalytic activity following sonocatalysis and photocatalysis processes, i.e, ∼48% and ∼65% in 3 h, respectively. The synergic effect of the sonocatalysis and photocatalysis processes had shown an excellent degradation of 81% in 3 h. To determine the reactive species responsible for the degradation of MB dye, a scavenger test was also performed using isopropyl alcohol (IPA), ethylenediaminetetraacetic acid (EDTA), and benzoquinone (BQ) scavengers. The degree of MB dye degradation was quantified by a phytotoxicity test on “Vigna radiata” seeds. Furthermore, the potentiality of BST ceramic was explored for water cleaning applications while irradiating it to solar radiation in real-time conditions.     

Structural properties of (Bi0.5Na0.5)1−xBaxTiO3 lead-free piezoelectric ceramics

A systematic XRD investigation of poled and unpoled ceramics of the system (1 ? x) Bi_0.5Na_0.5TiO₃–x BaTiO₃ (0 ≤ x ≤ 0.2) (BNBT) was performed. The variation of the lattice parameters confirms the existence of a morphotropic phase boundary at 0.06 ≤ x ≤ 0.08; however, significant differences in unit cell parameters between poled and unpoled states appear. Lattice distortions of the rhombohedral and tetragonal phases are significantly increased in poled samples. Dramatic changes in peak intensities of the pseudo-cubic (2 0 0) reflections between poled and unpoled samples reveal a strong enhancement of the tetragonal volume fraction in the poled state. Temperature-dependent XRD studies confirm a transition into a cubic high-temperature phase. This transition is rather smooth in the unpoled state. In poled samples, the tetragonal distortion and the tetragonal volume fraction display a different temperature variation and tetragonal regions seem to persist into the cubic phase field.     

The characterization of the barium titanate ceramic powders prepared by the Pechini type reaction route and mechanically assisted synthesis

BaTiO₃ ceramic powders were prepared by a complex method based on the Pechini type reaction route and mechanically assisted synthesis. In both ways BaTiO₃ ceramics were sintered after 120 min on 1300 °C without pre-calcination steps. The crystal structure was investigated by the XRD, IR and Raman spectroscopy. The particle size and morphology of BaTiO₃ were examined by XRD and SEM. The XRD results of powders indicate the formation of cubic phase of BaTiO₃. It can be observed that in the case of Pechini process BaTiO₃ powder is well crystallized but in the case of mechanochemistry process, significant amount of amorphous phase was detected. The sintered BaTiO₃ ceramic sample prepared by Pechini process, shows the formation of tetragonal phase. However, IR and Raman spectrum showed a mixture of cubic and tetragonal for BaTiO₃ obtained by Pechini process and tetragonal for BaTiO₃ obtained by mechanically assisted synthesis.     

Barium titanate‐based nanodielectrics of two chemically recyclable thermosets

In this work was investigated the effect of the addition of barium titanate (BaTiO₃) on electrical properties of two chemically recyclable thermosets, polyhemiaminal (PHA) and polyhexahydro‐s‐triazine (PHT), both fabricated from 4,4′‐oxydianiline (ODA), an ether derivative of aniline and paraformaldehyde. Thermal and mechanical properties as well as chemical recyclability of the two polymers and their nanocomposites/nanodielectrics were also investigated. In addition, a quantitative analysis was conducted of the nanoparticle dispersion in the PHA‐/PHT‐based BaTiO₃‐containing nanocomposites using transmission electron microscopy imaging and the nearest‐neighbor distance index and this index was used to analyze the investigated properties in connection with the proper mechanisms. Regarding the electrical properties for both neat polymers, conductivity values of the order of 10^?8 S m^?1 at 100 Hz were observed and dielectric constant values close to 2.80 for both polymers at 1 kHz. The addition of 0.5 wt% of BaTiO₃ ferroelectric nanoparticles increased by about 44% the dielectric constant (1 kHz) and conductivity (10² Hz) of the PHA‐based nanocomposite. PHA and PHT exhibited glass transition temperature (T_g) values in the range 125–180 °C. An increase of 7 °C in T_g was observed after the incorporation of 0.5 wt% of BaTiO₃ into PHA. Concerning the mechanical properties, values in the range 4.00–4.45 GPa for reduced modulus and 0.30–0.43 GPa for nanohardness for PHA and PHT polymers were observed. Independently of filler content or polymer matrix, both mechanical properties were enhanced after the addition of BaTiO₃. The chemical recycling of PHA/PHT and all nanocomposites in the initial ODA reagent after sulfuric acid treatment was successfully characterized using the NMR and Fourier transform infrared spectroscopic techniques. © 2018 Society of Chemical Industry