Pure BaTiO3 Research Articles

The effect of silica addition on dielectric properties of barium titanate nanoparticles

The effect of silicon dioxide (SiO2) nanoparticles on the dielectric constant was studied. Different weight percentages of silica (3, 5, and 7 %) were added to BaTiO3 nanoparticles. The structure, morphology, and dielectric properties were obtained using X-ray diffraction (XRD) and scanning electron microscopy (SEM), and an LCR meter. The diffraction patterns were shown that the crystallite size of BaTiO3 increased with the addition of SiO2. The dielectric constant and the dielectric loss were measured with various temperatures ranging from 27 to 180 °C at a constant frequency of 10 kHz. It was found that the value of the dielectric constant for the pure BaTiO3 is the highest at the Curie temperature (128 °C). The Curie temperature shifted to a higher value and the dielectric constant was decreased when the silica was added to BaTiO3. Moreover, with increasing the silica percentage, the variation in the dielectric loss values with the temperature was observed.

Photoluminescence and density functional theory analysis of BaTio3: Mn

Magnetic and photoluminescence properties of pure BaTiO3 and doped BaTiO3: Mn compounds were studied experimentally and theoretically. The broad band of high intensity observed in the photoluminescence spectrum covers the visible region (400–650 nm). This maximum coincides with the emission lines due to the 1T4---6A1 interatomic optical transition of the Mn ion and dramatically increases the photoluminescence intensity over a large region due to the absorbed photon energy. Results from the Color Calculator CRI show that this combination is suitable for display (and lighting) and white light emitting diode applications.Optical and magnetic properties of pure and doped BaTiO3:Mn compounds studied based on a larger supercell size of 180 atoms from first principle. With the replacement of Mn atoms, the peak of the optical spectrum for the imaginary part of the dielectric function shifts towards lower energies due to the reduction of the band gap. The ferromagnetic phase is stable for the structure regardless of the concentration of Mn atoms.

Ab initio study of samarium doped barium titanate

We used the density functional theory with spin polarization to investigate multifunctional properties of the Sm-doped BaTiO3 system (Ba1– x Sm x TiO3). The self-consistent calculation results were used to analyze the ferromagnetic and dielectric properties. The spontaneous electric polarization was estimated from the King-Smith and Vanderbilt theory and 1s core-hole absorbing atom was used to calculate the oxygen K-edge XANES spectra. The Hubbard correction has been considered over the rare-earth f-electrons. Results for x = 0.125 revealed a narrow band-gap energy, showing an enhanced ferroelectric character, with a spontaneous polarization higher than the reported for the pure tetragonal BaTiO3. On the other hand, the magnetic properties have been also confirmed, with a total magnetization value around 5.90 µB/cell, which have been mainly ascribed to the inclusion of the Sm cation into the BT crystalline structure.

Unique electric and dielectric features of dipole-pair substituted barium titanate ferroelectric ceramics (I): electrical characterization

A comparison study of pure barium titanate BaTiO3, dipole-pair [Ga3+, Ta5+] substituted barium titanate Ba(Ga3+, Ta5+)0.005Ti0.99O3 ([Ga3+, Ta5+]: BaTiO3), single ion [Ga3+] substituted barium titanate Ba(Ga3+)0.01Ti0.99O3 ([Ga3+]: BaTiO3), and single ion [Ta5+] substituted barium titanate Ba(Ta5+)0.01Ti0.99O3 ([Ta5+]: BaTiO3) ferroelectric ceramics have been conducted in order to discern the unique electric and dielectric properties derived from dipole-pair substitution. The band gap, DC resistivity, relative permittivity, dissipation factor, and complex impedance have been measured and analyzed. The dipole-pair substituted material is demonstrated to be an excellent dielectric, which possesses high electrical resistivity, high activation energy, significant dielectric diffuseness, high relative permittivity and low dissipation factor, due to charge compensation and creation of dipole-pairs in barium titanate solid solution ceramic matrix. The single substituted (acceptor and donor, respectively) samples behave more like traditional semiconductors, which have lower electrical resistivity, lower activation energy, and exhibit strong dielectric anomaly and large dissipation factor due to charge imbalance (electrons and holes) in part compensated for through additional defect creation. The relaxor-like behavior of the dipole-pair substituted sample is distinguishable from the classic relaxor through electric properties and structural phase diagram and is anticipated to spark more attention and further exploration. The unique features of electric resistivity and dielectric diffuseness of the dipolar-pair engineered BaTiO3 affords opportunity for designing properties of novel relaxor-like ferroelectrics.

Tuning electrical properties of BaTiO3 with iron modification

BaTiO3 plays an important role in advanced functional devices owing to its fascinating properties. Though it is an excellent ferroelectric material, its magnetism can be switchable via suitable modification. In this report, we have studied iron-modified BaTiO3, which has been prepared using cost-effective high-temperature solid-state reaction techniques. The Fe-modified BaTiO3 maintains its crystallinity in the tetragonal phase with P4mm space group with a slight variation of tetragonality ratio to 1.002 from 1.008 of BaTiO3 of the identical synthesis method. This is confirmed by Rietveld refinement. Field emission scanning electron microscopy (FESEM) and EDX (energy dispersive X-rays) spectrum along with an elemental mapping analysis has provided the feature of the Fe-modifed BaTiO3. Atomic force microscope (AFM) has been employed to get the detailed surface topology (2D and 3D) and surface roughness of the developed systems. This deformation caused by the incorporation of Fe significantly modifies the electrical properties of barium titanate. The ferroelectric-paraelectric phase transition temperature (Tc) of Fe-modified BaTiO3 has been diffused and shifted to 300 °C from 120 °C of pure BaTiO3, suggesting the materials for the high-temperature capacitive application. The room temperature M-H hysteresis of Fe-modified BaTiO3 indicates the ferromagnetism developed in the BaTiO3 with the introduction of Fe. The ac conductivity is in the order of 10−4 Ω−1cm−1, and its frequency response obeys Jonscher's power law. Different charge carriers are responsible for diverse conduction processes in different temperature ranges confirmed by the Arrhenius plot. Impedance spectroscopy studies reveal the existence of NTCR characteristics of the developed system. Well defined ferroelectric hysteresis loop indicates the existence of ferroelectricity in the developed system. The analysis of various electrical parameters has provided information on the material's dielectric relaxation and conduction mechanisms for possible application in functional devices.

Influence of Ca doping in structural, electronic, optical and mechanical properties of Ba1−xCaxTiO3 perovskite from first-principles investigation

Nowadays, perovskite materials are well known for electronics and optoelectronics applications. We have investigated a potential candidate for those applications to compare the applicability in optoelectronics, photorefractive and photovoltaic (PV) devices. The systematic comparative study of the structural, electronic, optical, mechanical, and thermodynamic properties of pure BaTiO3 and Ca doped BaTiO3 (Ba1−xCaxTiO3 where x = 0.125, 0.25, 0.375, 0.500, 0.625) perovskite have been carried out using first-principles and density-functional-theory calculations as recently this material was mostly experimented. The measured structural parameters from the geometrically optimized structure of cubic BT ceramic compared with the other theoretical values. A crystal phase transition occurs when doping content x = 0.25. The electronic band structure shows that the nature of the bandgap is changed from indirect bandgap to direct bandgap energy at G-point after doping the Ca atom into BaTiO3 (BT) crystal. Doping of Ca into BT has led to bandstructure modification including conduction band (CB) shifting toward the higher energy level. Electronic properties have been reported to examine the contribution of different orbitals to the CB and to the valance band (VB). This study investigated the modification of optical properties such as absorption, reflectivity, refractive index, extinction coefficient, conductivity, dielectric function and loss function at the energy range from 0 to 30 eV. The prominent absorption peak and optical energy were observed at the UV light energy region. Based on the optical behavior of the material this theoretical research suggests that the doped BT solution is a suitable candidate for photorefractive and optoelectronic devices. Different elastic constants reveal mechanical stability and the existence of the covalent bond of those compounds. Debye temperature increases with doping content. Hence modification of BaTiO3 crystal by Ca atom significantly develop various properties that led it to multifunctional applications.

Sol-gel synthesis, structural, morphological, X-ray photoelectron spectroscopy and magnetic properties of Cd doped BaTiO3 nanostructures

The present study reports the new functionality of room temperature ferromagnetism (RTFM) in non-magnetic Cadmium (Cd) doped BaTiO3 nanostructures, contrary to pure diamagnetic BaTiO3. TEM images show that grain size reduces with Cd doping. XPS analysis indicates that cation vacancies induce RTFM in Cd doped BaTiO3. Magnetic study reveals that pure BaTiO3 exhibits diamagnetic like signature, while Cd doped BaTiO3 show ferromagnetic feature with saturation magnetization (Ms ∼ 9.70x10-3 emu/g), remanent magnetization (Mr ∼ 0.22x10-3 emu/g) and coercive field (Hc ∼ 42.54 Oe), respectively. The current investigation also indicates that the induced RTFM could meet the demand of developing spintronic applications.

Enhanced Photocatalytic and Anticancer Activity of Zn-Doped BaTiO3 Nanoparticles Prepared through a Green Approach Using Banana Peel Extract

Perovskite barium titanate (BaTiO3) has received a lot of interest due to its extraordinary dielectric and ferroelectric properties, along with its moderate biocompatibility. Here, we investigated how Zn doping tuned the physicochemical characteristics, photocatalytic activity, and anticancer potential of BaTiO3 nanoparticles synthesized from banana peel extract. XRD, TEM, SEM, EDS, XPS, BET, Raman, and PL were utilized to characterize the as-synthesized pure and Zn (1 and 3 mol%)-doped BaTiO3 nanoparticles. All of the synthesized samples showed evidence of the BaTiO3 tetragonal phase, and the XRD patterns of the Zn-doped BaTiO3 nanoparticles showed the presence of a Zn peak. The particle size of BaTiO3 decreased with increasing levels of Zn doping without morphological changes. After Zn doping, the PL intensity of BaTiO3 decreased, suggesting a lower electron–hole recombination rate. BET analysis found that the surface area of Zn-doped BaTiO3 nanoparticles was higher than that of pure BaTiO3. Under visible irradiation, the photocatalytic activity of pure and Zn-doped BaTiO3 nanoparticles was compared, and a remarkable 85% photocatalytic activity of Zn (3%)-doped BaTiO3 nanoparticles was measured. As a result, Zn-doped BaTiO3 nanoparticles are recognized as excellent photocatalysts for degrading organic pollutants. According to cytotoxicity data, Zn (3%)-doped BaTiO3 nanoparticles display four-fold greater anticancer activity against human lung carcinoma (A549) than pure BaTiO3 nanoparticles. It was also observed that Zn-doped BaTiO3 nanoparticles kill cancer cells by increasing the intracellular level of reactive oxygen species. Furthermore, compared to pure BaTiO3, the Zn-doped BaTiO3 nanostructure showed better cytocompatibility in non-cancerous human lung fibroblasts (IMR90). The Zn-doped BaTiO3 nanoparticles have a reduced particle size, increased surface area, and a lower electron–hole recombination rate, which are highly beneficial for enhanced photocatalytic and anticancer activity. Overall, current data showed that green-fabricated Zn-BaTiO3 nanoparticles have superior photocatalytic and anticancer effects along with improved biocompatibility compared to those of pure BaTiO3. This work underlines the significance of utilizing agricultural waste (e.g., fruit peel) for the fabrication of BaTiO3-based nanostructures, which hold great promise for biomedical and environmental applications.

Investigation of local structure and phase transformation in Ce-doped barium titanate and correlation with electrical properties

ABSTRACT BaTiO3-based materials are used as the replacement for lead-based perovskite materials for its wide dielectric applications. But the substitution of different doping elements in pure BaTiO3 drastically affects the microstructure, phase transition behavior and electrical properties. In the present work, local structure, phase transformation and dielectric behavior of BaCexTi1-xO3 (BCT) ceramics were studied for compositions x = 0.02, 0.05 and 0.1. A diffuse phase transition from orthorhombic to cubic via tetragonal in BCT with increasing Ce content was observed. An increase in particle size with Ce doping concentration was observed in FESEM images. Spherical and cuboid-shaped particle in the order of 80–150 nm was observed in transmission electron microscopic (TEM) images. RAMAN spectra confirm the tetragonal to cubic phase transition. Local structural and phase transformation behavior was obtained from laboratory-based PDF and XRD, respectively. Change in PDF was observed due to an increase in Ce doping. Dielectric properties decreased for Ce mole fraction of x = 0.1.

Enhancement of Photocatalytic Activity and Microstructural Growth of Cobalt-Substituted Ba1−xCoxTiO3 {x = 0, …, 1} Heterostructure

The photocatalytic degradation process and absorption kinetics of the aqueous solution of the Cibacron Brilliant Yellow 3G-P dye (Y) were investigated under UV-Vis light. Pure barium titanate BaTiO3 (BT) and cobalt ion-substituted barium Ba1−xCoxTiO3 (x = 0, …, 1) nano-compound powders (BCT) were synthesized using the sol–gel method and colloidal solution destabilization, and utilized as photocatalysts. The powder X-ray diffraction (PXRD) crystal structure analysis of the BT nanoparticles (NPs) revealed a prominent reflection corresponding to the perovskite structure. However, impurities and secondary phase distributions were qualitatively identified in the PXRD patterns for x ≥ 0.2 of cobalt substitution rate. Rietveld refinements of the PXRD data showed that the BCT nano-compound series undergoes a transition from perovskite structure to isomorphous ilmenite-type rhombohedral CoTiO3 (CT) ceramic. The nanoparticles produced displayed robust chemical interactions, according to a Fourier transform infrared spectroscopy (FTIR) analysis. The BT and BCT nanoparticles had secondary hexagonal phases that matched the PXRD results and small aggregated, more spherically shaped particles with sizes ranging from 30 to 114 nm, according to transmission electron microscopy (TEM). Following a thorough evaluation of BCT nano-compounds with (x = 0.6), energy-dispersive X-ray (EDX) compositional elemental analysis revealed random distributions of cobalt ions. Through optical analysis of the photoluminescence spectra (PL), the electronic structure, charge carriers, defects, and energy transfer mechanisms of the compounds were examined. Due to the cobalt ions being present in the BT lattice, the UV-visible absorption spectra of BCT showed a little red-shift in the absorption curves when compared to pure BT samples. The electrical and optical characteristics of materials, such as their photon absorption coefficient, can be gathered from their UV-visible spectra. The photocatalytic reaction is brought about by the electron–hole pairs produced by this absorption. The estimated band gap energies of the examined compounds, which are in the range of 3.79 to 2.89 eV, are intriguing and require more investigation into their potential as UV photocatalysts. These nano-ceramics might be able to handle issues with pollution and impurities, such as the breakdown of organic contaminants and the production of hydrogen from water.

Tunable Phase Structure in Mn-Doped Lead-Free BaTiO3 Crystalline/Amorphous Energy Storage Thin Films

For dielectric energy storage materials, high polarization and high breakdown strengths are a long-standing challenge. A modulating crystalline/amorphous phase structure strategy is proposed by Mn-doping and annealing temperature to enhance the energy storage performance of pure BaTiO3 (BT) films. In this study, lead-free Mn-doped BT films were prepared on Pt/Ti/SiO2/Si substrates via the sol-gel method, and the effects of the crystalline/amorphous phase ratio on polarization and electric properties were analyzed. A small amount of Mn-doping in BT could reduce the annealing temperature and enhance polarization with an Mn content of 8%. In addition, the energy storage properties of BT-8%Mn films achieve the best energy storage performance in terms of energy density and efficiency of 72.4 J/cm3 and 88.5% by changing the annealing temperature to 640 °C. BT-8%Mn energy storage films also possess good stability over a wide temperature range of 20 °C–200 °C, which demonstrates that crystalline/amorphous engineering is a simple and effective way to enhance energy storage applications of dielectric films.

Giant dielectric constant and ac electrical conductivity: Cu and Cu/W incorporated perovskite BaTiO3

Gigantic relative permittivity and ac electrical conductivity characteristics were realized in BaTiO3 through incorporation of Cu2+ and Cu2+/W4+ ions. The XRD results evidenced that pure BaTiO3 powder has a single phase with tetragonal structure. In Cu doped and (Cu, W) codoped samples, α-Ba2TiO4 phase with ratio of 17–25% was formed into BaTiO3 powder. The crystal analysis proved that the formed α-Ba2TiO4 phase naturally decay with time or heating at high temperature. The SEM micrographs illustrated the formation of elongated connected network particles in Cu doped and (Cu, 1%W) codoped BaTiO3 while cauliflower-like grains were seen for (Cu, 3% W) codoped BaTiO3 sample. Pure BaTiO3 powder reveals an ultraviolet (UV) absorption edge, corresponding to band gap energy of 3.25 eV. Owing to Cu2+ doping and (Cu2+, W4+) codoping, the absorption edge of BaTiO3 structure was powerfully red shifted and displayed oblique lines, matching to band gap energies within 3.06–2.68 eV. Pure BaTiO3 reveals a relative permittivity value of 811 (42 Hz) which transferred to gigantic values of (7.01572 × 105), (9.54016 × 105) and (3.00234 × 105) after insertion of Cu2+ and (Cu2+, W4+) ions. For Cu doped and (Cu, 1% W) codoped BaTiO3, the giant relative permittivity was considerably increased with temperature up to 125 °C and until 150 °C for (Cu, 3% W) codoped BaTiO3 sample. After decomposition of α-Ba2TiO4 phase (α-Ba2TiO4 → BaTiO3 + BaO), the dielectric constant still reveals stable colossal values equal to (7.5300 × 104), (3.66431 × 105) and (1.2277 × 104) at frequency of 42 Hz for Cu doped, (Cu, 1% W) and (Cu, 3% W) codoped BaTiO3, respectively.

First-Principle Study on Correlate Structural, Electronic and Optical Properties of Ce-Doped BaTiO3

The structural, electronic, and optical properties of pure and Ce-doped BaTiO3 were investigated based on first-principle calculation. Here, we concentrate on understanding the effect of the substitution of Ce for Ba and Ti sites in the equilibrium lattice parameters, DOS, electronic band structure, and optical performance of the materials. The crystal structures with a 12.5% doping ratio at different sites were constructed by superseding an atom of Ba (or Ti) site with a Ce atom and investigating the optimized crystal structure parameters. The substitution of Ce leads to a reduction in the band gap by inducing the movement of the conduction band minimum (CBM) and valence band maximum (VBM). The reduction in the band gap has been shown to be beneficial in increasing electrical conductivity. The density of states of the materials was calculated to gain insight into the valence band, conduction band, and contribution of each orbital to the total density of states in the electronic structure. The charge density, Mulliken charges, and bond overlap populations of pristine and Ce-doped BaTiO3 were calculated to understand the nature of chemical bonds before and after doping. In addition, the optical properties of the materials were calculated, and the substitution of Ce for Ba site increased the static dielectric constant. In contrast, it decreased when Ce was doped into the Ti site. The substitution of Ce for different sites reduced the reflectivity of the material, while the transparency of the materials before and after doping was almost the same. The materials were transparent to incident light when the photon energy was below 10 eV, whereas opacity was in the ultraviolet range of 10–13 eV and beyond 20 eV. The theoretical calculation of different properties provides a new idea for the theoretical study of the BaTiO3-based system.

Performance of Ni-doped BaTiO3 hollow porous spheres supported reduced graphene oxide as an efficient bifunctional electrocatalyst for oxygen evolution reaction and oxygen reduction reaction

Perovskite oxides are promising and effective electrocatalysts for various energy related applications due to their low cost, versatile structures, as well as interesting catalytic activity. Herein, aerosol spray pyrolysis was used to synthesize hollow spherical structure of BaTiO3, Ni-doped BaTiO3 and Ni-doped BaTiO3 supported on reduced graphene oxide (rGO). The prepared nanocomposites were used as bifunctional electrocatalysts simultaneously for oxygen reduction and oxygen evolution reactions. Several characterization techniques were utilized for characterizing the prepared materials. The morphological analysis revealed that the produced spheres consisted of nanoparticles ranging in size from 5 to 20 nm, while the Brunauer–Emmett–Teller surface analysis assured the high mesoporous features of the prepared hollow spheres. The oxygen evolution reaction (OER) results exhibited an exceptional current density up to 80 mA cm−2 at potential 1.6 V vs. RHE, this performance was five times higher than the pure BaTiO3 (BTO). The Tafel slope was reduced by 75.5 % compared to BaTiO3. Ni-doped BaTiO3/rGO hollow porous spheres show excellent OER electrocatalytic activity compared to the commercial IrO2 electrocatalyst in basic medium. Moreover, the prepared Ni-doped BaTiO3/rGO hollow porous spheres presented excellent catalytic activity for oxygen reduction reaction (ORR), mainly favored a direct four-electron pathway, enhanced the charge transfer, led to the lowest onset potential (0.77 V vs RHE), and also achieved excellent long-term durability. The results demonstrated that the prepared perovskite/rGO composites effective bifunctional electrocatalysts.

High‐Efficiency Reactive Oxygen Species Generation by Multiphase and TiO6 Distortion‐Mediated Superior Piezocatalysis in Perovskite Ferroelectrics

AbstractPiezocatalysis, governed by piezo‐potential within piezoelectrics, has gained prominence for reactive oxygen species (ROS) generation, which is significant to environmental and biological applications. However, designing piezocatalysts with excellent piezocatalytic performance in a wide temperature and efficient charge carrier separation ability is still challenging. Herein, eco‐friendly BaTiO3 (BT)‐based perovskite ferroelectrics with tailored multiphase coexistence in a wide temperature range are constructed to boost higher piezoelectricity and large piezo‐potential, which is attributed to decreased polarization anisotropy by flat Gibbs energy profile. Elevated piezo‐potential in designed BT‐based piezocatalyst guarantees high‐efficient generation rate of •OH (200 µmol g−1 h−1) and •O2− (40 µmol g−1 h−1) by ultrasound stimulation, which is 3.5 times more than that of pure BT. Besides, piezocatalytic capacity to degrade dye wastewater shows a rate constant of 0.0182 min−1 and gives an antibacterial rate of 95% within 30 min for eliminating E. coli. Theoretical simulations validate that the local distortion of TiO6 octahedra also contributes to piezocatalytic performance by inducing electron–hole pairs separation in real space, and better response to slight structural deformation. This work is important to design high‐performance piezocatalysts with high‐efficiency ROS generation for sewage treatment and sonodynamic therapy.

Enhanced optical and thermal conductivity properties of barium titanate ceramic via strontium doping for thermo-optical applications

In this study, we prepared a homogeneous fine powder of barium titanate (BaTiO3, BT) doped with different concentrations of strontium (x = 0, 0.05, 0.125, 0.15, 0.20, and 0.3) and having the composition Ba1-xSrxTiO3 (barium strontium titanate, BSrxT). XRD patterns and Rietveld refinement revealed the existence of a single tetragonal phase structure for BSrxT, x = 0–20%, and a single cubic structure for BSr30%T. The physical properties of the pure and doped mixtures were studied. The results showed that the addition of strontium to the physical properties of BaTiO3, including the apparent porosity, bulk density, linear shrinkage, and water absorption have been changed when increasing the Sr content. Moreover, the inclusion of 15% Sr in BaTiO3 increases the apparent porosity and water absorption of the sample to 6.2 and 28.5%, respectively. The optical properties were investigated by Ultraviolet–visible spectroscopy and it was found that the optical band gap decreases significantly with increasing Sr concentration, from 3.10 for pure BaTiO3 to 2.46 eV for the BSr30%T compound. The thermal conductivity measurements showed that the doping mechanism and the increased temperature have a significant effect on the thermal conductivity results of the fabricated ceramic materials. Therefore, it was found that the value of thermal conductivity increases with increasing Sr doping and at higher temperatures. A correlated behavior of optimum values is observed in band gap energy, absorption, and thermal conductivity which can be exploited for thermo-optical applications.

Solvothermal synthesis of nanoscale BaTiO3 in benzyl alcohol-water mixtures and effects of manganese oxide coating to enhance the PTCR effect.

A solvothermal method using various benzyl alcohol/water solvent mixtures has been used to synthesise phase pure nanocrystalline BaTiO3 samples with varying particle sizes in the range of 11-139 nm. The crystallite/particle size of BaTiO3 shows an overall decrease as the benzyl alcohol percentage increases, especially at higher percentages (≥80%) of benzyl alcohol. The decrease in crystallite/particle size can be attributed to the increased viscosity of the solvent mixture when raising the percentage of benzyl alcohol. A manganese oxide coating applied to the BaTiO3 surface had a negligible impact on its microstructure and morphology, but significantly enhanced the observed positive temperature coefficient of resistance. This research has been carried out to allow the development of smaller BaTiO3 particles for use in new battery, capacitor and thermistor technologies, whilst maintaining the PTCR property of the material that is typically observed in larger particle sizes.

A novel NiO/BaTiO3 heterojunction for piezocatalytic water purification under ultrasonic vibration.

This work designed and prepared a novel heterojunction composite NiO/BaTiO3 through a method of photodeposition and used it in piezocatalytic dye removal for the first time. Results of the piezocatalytic test indicated that the NiO/BaTiO3 composite presented superior efficiency and stability in the RhB degradation under the vibration of ultrasonic waves. The best NiO/BaTiO3 sample synthesized under light irradiation for 2h displayed an RhB degradation rate of 2.41h-1, which was 6.3 times faster than that of pure BaTiO3. By optimizing the piezocatalytic reaction conditions, the degradation rate constant of NiO/BaTiO3 can further reach 4.14h-1 A variety of systematic characterizations were executed to determine the reason for the excellent piezocatalytic performance of NiO/BaTiO3. The band potentials of NiO and BaTiO3 are found to coincide, and at their contact interface, they may create a type-II p-n heterojunction structure. Driven by the potential difference and the built-in electric field, piezoelectrically enriched charge carriers can migrate between NiO and BaTiO3, resulting in improved efficiency in charge separation and an increase in the piezoelectric catalytic performance. This study may provide a potential composite catalyst and a promising idea for the design of highly efficient catalysts in the field of piezoelectric catalysis.

Study of ferroelectric and piezoelectric response of heat-treated surfactant-based BaTiO3 nanopowder for high energy capacitors

Barium titanate (BaTiO3) nanopowder was synthesized by the alkoxide-hydroxide sol–gel process in an inert (N2) atmosphere. The effect of surfactant sodium dodecyl sulfate (SDS) concentration on the dispersion of BaTiO3 powder was studied at different sintering temperatures, under microwave heating. The phase and structural analysis revealed that the addition of surfactant did not affect the phase transformation of barium titanate. The best outcome was obtained in the case of 0.5 % surfactant-based BaTiO3. At 1100 °C sintering temperature, 0.5 % surfactant-based BaTiO3 exhibited a maximum density of 97.7 %, dielectric constant of 9488, the leading parameters of breakdown strength as 3.12 kV/cm, the figure of merit as 9.98 × 103, and the piezoelectric constant (d33) as 153 pC/N. Moreover, the energy density of 86 kJ/m3 with an energy efficiency of 27.43 % was attained at 1100 °C. For pure BaTiO3 nanopowder, the energy density and the energy efficiency were found as 66.85 kJ/m3 and 50.42 % at 1250 °C, respectively.

Application of a piezo-photocatalytic thin film (FTO/BaTiO3/SnO2) for enhanced degradation of organic pollutants and disinfection of wastewater

In recent years, the removal of organic pollutants (dyes and pharmaceuticals) and microbes from polluted water has remained a significant concern. We report a novel biosynthesized SnO2 loaded fluorine-doped tin oxide/barium titanate (FTO/BTO) thin film for piezo-photocatalytic degradation of methyl orange (MO), methylene blue (MB) and ciprofloxacin (CIP), as well as for the removal of gram-negative E. coli and gram-positive S. aureus bacteria from water. Piezo-photocatalyst thin films were characterised using XRD, FTIR, FE-SEM, TEM, TGA, BET, XPS, PL and UV-DRS spectroscopy. The deposition of the small spherically shaped SnO2 nanoparticles on the surface of BaTiO3 was confirmed by TEM, EDS and FTIR. Chronoamperometry and electrochemical impedance spectroscopy (EIS) were employed to determine piezo-electrochemical properties of the prepared piezo-photocatalyst thin films. The results showed that BaTiO3 loaded with SnO2 on its surface, exhibited a higher piezo-electrochemical current than pure BaTiO3 (BTO). FTO/BaTiO3@0.2%SnO2 generated about 1.3 mA current under ultrasonic vibration, which is more than 6 times that of pure FTO/BaTiO3. Furthermore, FTO/BaTiO3@0.2%SnO2 showed a better degradation efficiency of 94, 92 and 64% for MO, MB and CIP, respectively. Additionally, BaTiO3@0.2%SnO2 was shown to have a higher antibacterial activity against gram-negative E. coli bacteria than against gram-positive S. aureus bacteria. Overall, this study showed that the piezo-photocatalytic activity of BaTiO3 could be improved through SnO2 loading. Moreover we were able to demonstrate that BaTiO3/SnO2 composites may be employed as multifunctional catalysts based on their ability to break down various organic contaminates (dyes and pharmaceutical pollutants), and to remove bacteria from wastewater.