Titanate Samples Research Articles

Engineered Electron-Deficient Sites at Boron-Doped Strontium Titanate/Electrolyte Interfaces Accelerate the Electrocatalytic Reduction of N2 to NH3: A Combined DFT and Experimental Electrocatalysis Study.

The development of an efficient, selective, and durable catalysis system for the electrocatalytic N2 reduction reaction (ENRR) is a promising strategy for the sustainable production of ammonia. The high-performance ENRR is limited by two major challenges: poor adsorption of N2 over the catalyst surface and abysmal N2 solubility in aqueous electrolytes. Herein, with the help of our combined density functional theory (DFT) calculations and experimental electrocatalysis study, we demonstrate that concurrently induced electron-deficient Lewis acid sites in an electrocatalyst and in an electrolyte medium can significantly boost the ENRR performance. The DFT calculations, ex situ X-ray photoelectron and FTIR spectroscopy, electrochemical measurements, and N2-TPD (temperature-programmed desorption) over boron-doped strontium titanate (BSTO) samples reveal that the Lewis acid-base interactions of N2 synergistically enhance the adsorption and activation of N2. Besides, the B-dopant induces the defect sites (oxygen vacancies and Ti3+) that assist in enhanced N2 adsorption and results in suppressed hydrogen evolution due to B-induced electron-deficient sites for H+ adsorption. The insights from the DFT study evince that B prefers the Srtop position (on top of Sr) where N2 adsorbs in an end-on configuration, which favors the associative alternating pathway and suppresses the competitive hydrogen evolution. Thus, our combined experimental and DFT study demonstrates an insight toward enhancing the ENRR performance along with the suppressed hydrogen evolution via concurrently engineered electron-deficient sites at electrode and electrolyte interfaces.

Influence of the TiO2 crystalline phase on the performance of UVA/brookite/persulfate and UVA/anatase/persulfate systems for the degradation of isothiazolinones in aqueous matrices

The activation of persulfate (PS) under UVA irradiation by two TiO2 polymorphs (brookite and anatase) and titanate photocatalysts was evaluated for the simultaneous removal of the biocides methylisothiazolinone (MIT) and chloromethylisothiazolinone (CMIT), in ultrapure water and real sewage treatment plant water (SW). Titania and titanate samples were synthesized by a hydrothermal method and characterized by XRD, SEM, N2 adsorption-desorption isotherms and UV-Vis DR. The reactions were performed in individual (brookite, anatase, titanate and PS) and hybrid (titania/PS and titanate/PS) systems and compared to those with TiO2-P25 as reference. In ultrapure water, the combined brookite/PS system showed a higher performance for MIT and CMIT abatement and a stronger synergistic effect between titania and PS than found in anatase/PS and titanate/PS systems, indicating the higher effectiveness of the brookite phase for PS activation under UVA. The use of SW water revealed the strong inhibitory effect of matrix constituents in the individual brookite, anatase and PS systems, which exhibited a low performance. However, the kinetics of MIT/CMIT in SW were greatly enhanced in the hybrid TiO2/PS systems, especially with brookite, leading to an efficient degradation of both pollutants and the decrease of total organic carbon (TOC). The addition of chemical scavengers showed a similar reactivity of HO• towards both isothiazolinones whereas a preferential attack of SO4•− to MIT was observed, demonstrating the selective nature of SO4•−.

Study and Characterization of Copper and Titanium Oxides Nanostructures for Some Molecular and Biological Applications

In this work, Copper and Titanium nanocomposites (NPs) were prepared by mixture exchange process with ratios (25, 50 and 75 % CuO-TiO2). The biological activity was studied, and it was found that the concentrations of 50 and 100 µg/mL of 50 and 75 % CuO-TiO2 were the best concentrations, Low concentrations of the nanoparticle mixture at 25 µg/mL also stimulated the growth of symbiotic bacteria. The mixture of nanoparticles was easier to prepare and more effective in inhibiting bacterial growth. biochemical test and PCR were performed to confirm the identity of the studied bacteria. While isolating the bacteria, a new type of bacteria was detected and registered in the Global Gen Bank under accession No. OP942239. Surface and structure properties have been studied using FESEM, EDS analysis, XRD and FTIR respectively. It can be seen that the size and diameter of the nanocomposite increase with the weight ratio of CuO-TiO2. The aggregated CuO-TiO2 nanostructures with different ratios were transformed gradually into a uniform spherical shape. The average size of the CuO/TiO2 composite was found to be about 32.122, 29.865 and 27.607 nm at 25, 50 and 75 % CuO-TiO2 respectively. While the mean sizes of CuO and TiO2 were 25.35 and 34.38 nm respectively. The crystalline size decreases after the ion exchange process, which could be due to the diffraction peaks being broad in all the samples of Copper Titanate at the surface. Subsequently, adding Copper particles to the TiO2 film can improve the performance of the material. HIGHLIGHTSThe nanostructure CuO-TiO2 was created through various loading ratios. These NPs’ efficiency was calculated using a number of techniques, including FTIR, X-ray diffraction, EDS spectra, and FESEM. The observations indicate that molecular transition parameters play an essential role in determining the size, shape, and functionality of CuO- TiO2 NPs. The sharp peaks observed in the composites indicated higher crystallinity in CuO. In addition, two types of NPs have shown promising effects in inhibiting NPs aggregation and enhancing biological effects but the potential of these NPs against different bacteria may differ. Thus, further research and testing is needed to assess its efficacy and human health and environmental impact before considering its use. In conclusion, copper and titanium NPs have their distinct advantages in bacterial inhibition, and the choice between them should be based on specific conditions and environmentally friendly factors. GRAPHICAL ABSTRACT

Structural and electrical characteristics of manganese modified BaTiO3 ceramic

The material Ba(Ti0.5Mn0.5)O3 synthesized through the conventional solid-state reaction method has hexagonal structure free from any impurity phase. The complex dielectric dispersion, temperature and frequency-dependent dielectric, impedance, AC conductivity, and leakage behavior of the sample are studied. The impedance study of the material encloses non-Debye type relaxation, negative temperature coefficient of resistance nature and the grain and grain boundary effects. The ferroelectric to paraelectric phase transition occurs at T C ∼ 270 °C. The dielectric constant and loss-tangent values are found to be less as compared to that of the parent barium titanate sample. R g < R gb, that is, grain boundary has greater opposition than the grain region. The material follows correlated barrier hopping model. The carrier transport process through AC conductivity study obeys the Jonscher’s power law and the Arrhenius relation while varying with the frequency and temperature.

Development and optimization of PZT suspensions with high solid loading and low viscosity for stereolithography-based additive manufacturing

Achieving synergy between high solid loading and low viscosity for ceramic suspensions a critical issue in the field of stereolithography. In this work, we successfully obtained a well-dispersed PZT suspension with high solid loading (55 vol%) and low viscosity (3047.5 mPa s at 60 rpm) by adding appropriate amounts of dispersant (1 wt% KOS110) and thickening agent (2 wt% PEG300), providing a foundation for crack-free photosensitive lead zirconate titanate (PZT) samples. This work presented a simple approach for achieving synergy between the high solid loading and low viscosity of ceramic suspensions for stereolithography-based additive manufacturing.

Investigation of structural, dielectric, impedance, and mechanical properties of hydroxyapatite-modified barium titanate composites for biomedical applications

Abstract This report presents the synthesis of pristine barium calcium titanate (BCT) and composite samples of [x(HA)–100 − x(BCT)]; (0 ≤ x ≤ 20) through solid-state reaction with microwave sintering. Hydroxyapatite (HA)–BCT composites have been developed to minimize grain growth, thereby boosting the material’s physical, mechanical, and electrical properties. The evaluated samples were examined for the Fourier transform-infrared spectra, and the results showed a correlation with the X-ray diffraction patterns. The real and imaginary dielectric permittivity was applied to determine the AC conductivity, and the findings indicate a drop in the frequency exponent values (S) from 1 to 0.67 for samples with x = 0. Similarly, for samples with x = 5, the value of S decreases from 0.90 to 0.55. For samples with x = 10, the value of S reduces from 0.7 to 0.54. Lastly, for samples with x = 20, the value of S decreases from 0.63 to 0.45. The exponent S and temperature relationship may be attributed to a thermal activation mechanism. The grains and grain boundary resistivity were estimated using a Cole–Cole plot, and the results showed that the grain boundary resistivity is higher in comparison to the resistivity exhibited inside the grains. This demonstrated the distinct electrical conductivity at the interfaces between the grains in comparison to the interior of the grains. The analysis of hardness indicates that the average hardness of the samples ranges from 5.22 to 4.77 GPa, which is maintained at different HA concentrations. The data suggest that this composite may have the potential to be a biomedically helpful substance.

Temperature cycling effect on structural, optical and electrical properties of nanostructured sodium titanates

Sodium titanates represent a promising alternative for the construction of anodes for sodium-ion batteries. To study the electrical response of nanostructured sodium titanate samples under plausible temperature conditions, we evaluate the electrical impedance in the range of temperatures from −30 ∘C to 50 ∘C, and the effect of consecutive temperature cycling. Strong changes in electrical properties are observed during the first temperature cycle, followed by a stabilization in the consecutive cycles. This behavior is reversible when the sample is exposed to external conditions and room temperature for less than an hour. Probably a structural and surface water removal and a surface water reabsorption occur, affecting the charge carriers and with it the impedance. Structurally, no differences are detected before and after the cycles, nor when evaluating only the vacuum process. However, when the optical properties are evaluated we find non-reversible changes after the temperature cycles. The optical behavior after the temperature cycling becomes uniform, the same type of electronic defects become predominant and similar direct and indirect band gap values are obtained, regardless of the starting synthesis condition. These results have significant implications for potential technological applications of these materials.

Flash and Breakdown: Thermal Runaway and Dielectric Breakdown as Competing Mechanisms During Flash Sintering of Barium Titanate

Herein, hot‐spot generation in bulk barium titanate samples is investigated during controlled current ramping at various rates using in situ dilatometry. The incubation of the flash event is separated from dielectric breakdown at high current densities, which has previously been attributed to cause flash incubation in barium titanate. The lower boundary of the onset temperature of the flash event in barium titanate is investigated through conventional flash experiments at high electric fields. Despite incubating through thermal runaway, the lower boundary does not coincide with the Debye temperature of barium titanate.

Magnetic properties of CaCu3-xTi4-yFex+yO12 solid solutions: Valence state of iron ions and metamagnetic phase transitions

CaCu3-xTi4-yFex+yO12 (1 or 3%) solid solutions were synthesized using a solid state method, while 1 or 3 mas. % of iron (natural abundance of isotopes) was added to the stoichiometric amount of CaO, CuO and TiO oxides. CaCu3-xTi4-y57Fex+yO12 (3%) sample with a higher 57Fe isotope content was synthesized using the same technology for the detailed investigation by the Mӧssbauer spectroscopy. The structural and microstructural characteristics of calcium copper titanate samples were studied by X-ray diffraction, X-ray fluorescence analysis and scanning electron microscopy techniques. The magnetic properties were studied by Mӧssbauer spectroscopy, electron spin resonance and magnetometry methods. Based on all experimental data we can conclude that Fe ions substitute Ti4+ and Cu2+ positions in octahedral and planar oxygen environment, respectively. Such type of substitution leads to the appearance of three types of iron magnetic centers: divalent Fe2+ in the planar environment and trivalent Fe3+ in the symmetrical and distorted octahedral positions that strongly effects to the magnetic properties of the investigated samples. Most unique magnetic properties including the metamagnetic phase transitions are observed in CaCu3-xTi4-yFex+yO12 (3%) sample where both the significant amount of Fe3+ ions in distorted octahedral position together with Fe2+ are present.

Optical properties of calcium-doped barium titanate prepared by sol-gel route and microwave pre-treatment

Calcium doped barium titanate samples, Ba1-xCaxTiO3 (x = 0.00, 0.01, 0.05, 0.10, 0.15, 0.20) were prepared by sol-gel process followed by preheating in the microwave before calcination. The linear optical characteristics such as linear absorption coefficient, linear refractive index, linear extinction coefficient, optical conductivity; and nonlinear optical characteristics such as nonlinear refractive index and third order susceptibility for both calcined and sintered samples were studied. The free electron concentration due to the substitution of T4+ by Ca2+ is believed to be mainly responsible for the change of the optical properties. In fact, the latter seem to be strongly influenced by site occupation, density of the samples and the crystal structure. This new technique used in the synthesis of perovskite products may be the path to novel electro-optical applications.

Temperature Dependence of the Electrical Properties of Na2Ti3O7/Na2Ti6O13/POMA Composites.

The temperature dependence of the electrical properties of composites formed by biphasic sodium titanate and poly(o-methoxyaniline) (Na2Ti3O7/Na2Ti6O13/POMA) with different concentrations of POMA (0%, 1%, 10%, 15%, 35% and 50%) in the ceramic matrix was determined from measurements of complex impedance. The structural details were studied by means of X-ray diffraction, confirming the formation of the Na2Ti3O7/Na2Ti6O13/POMA composites. The displacement of the (200) reflection from 2θ = 10.45° to 11.15° in the composites with 10 and 15% of POMA suggested the partial replacement of H+ for Na+ in the Na2Ti3O7 structure. The thermal properties were investigated by Thermogravimetry and Differential Thermal Analysis. The Thermogravimetry curves of the composites with POMA content of 1, 10 and 15% presented profiles similar to that of pure sodium titanate sample. The composites with 35 and 50% of POMA showed a process at temperatures around 60–70 °C, which was associated with water absorbed by the polymer. The analysis of the complex impedance spectroscopy measurements revealed that the electrical resistivity of the composites in the range from 0 to 35% increased by two orders of magnitude, with different values for each concentration. This positive temperature coefficient of resistivity was less noticeable in the composite with highest POMA mass content (50%). The rapid increase in resistivity caused an increase in the relaxation time calculated from the time domain. The electrical response of the 50% of POMA compound changes in relation to what was observed in the other compounds, which suggests that there is a saturation limit in the increase in resistivity with POMA content.

Influence of sample thickness and cross-sectional area on flexoelectric effect under one-dimensional impact

The shock wave generates the strain gradient and consequent electric polarization in samples due to the flexoelectric effect during the impact process. At present, some scholars have studied the influence law of different impact velocities, but the influence of different thickness and cross-sectional area of samples on flexoelectric effect is still blank. In this letter, we have studied the voltage variation of barium titanate samples with different thickness and cross-sectional area under a certain impact velocity. The results show that the maximum voltage value caused by flexoelectric effect increases as the thickness increases, which is basically in positive proportion; it decreases with the increase of diameter, which is in inverse proportion. This research will lay a theoretical foundation for the fabrication of flexoelectricity sensor.

Ultra-fast high-temperature sintering of strontium titanate

Ultrafast High-temperature Sintering (UHS) is a novel sintering process enabling extremely high heating rates by direct contact of sample to electrically heated thin carbon strips. Using strontium titanate as a model system, the densification behavior by UHS was investigated. Controlled experiments via maximum current limitation were used to study the influence of the applied current on the degree of densification and resulting final grain size. Simulations by Finite Element Modeling (FEM) allow estimating the sample temperature reached during UHS, which is in good agreement with the experimental data. Moreover, the FEM simulations show a self-stabilization of the sample temperature by thermal radiation. UHS results suggest that rapid densification can be achieved with an extremely high heating rate. The microstructure of the undoped strontium titanate samples shows exaggerated grain growth and pore-boundary separation, which results in pore entrapment inside grains. The addition of 2 mol% iron in strontium titanate is beneficial by limiting the grain growth during the UHS sintering cycle. Uniform densification and grain growth in the sample is consequently observed. Scanning transmission electron microscopy/energy dispersive x-ray spectroscopy (STEM/EDS) is utilized to analyze grain boundary segregation. Measurement of the electrical conductivity of the UHS sintered samples by impedance spectroscopy suggest that rapid densification by UHS enables full access to the functional properties of strontium titanate as compared to the conventionally sintered material.

Effect of sintering on the piezoelectric properties and microstructure of lead free (Ba1-xCaxZr0.1Ti0.9O3) (x=0.065) ceramics

In this work, pellet samples of barium calcium zirconate titanate (Ba1-xCaxZr0.1Ti0.9O3, x=0.065) were prepared using solid state reaction route with double sintering. The structural and piezoelectric properties were measured. Further, SEM and EDAX analysis were observed. With different sintering temperature, the density and grain size of the prepared pellet samples were changed and further, their effect in piezoelectric properties has been observed. For the prepared samples, the converse piezoelectric constant (d33*) has been decreased with the increase in sintering temperature. The piezoelectric constant (d33*) was measured highest (153 pm/V) at 1300?C.

Utilization of thermal neutron induced in-situ chain reactions and the (n,p) reaction with fast neutrons for compositional characterization of lithium titanate

A methodology has been developed for the complete compositional characterization of lithium titanate (LTO) using neutron activation, which is quite challenging and no literature report is available so far. The concept of thermal neutron induced in-situ chain reactions 6Li(n,α)3H and 16O(3H,n)18F has been used for the determination of Li and O through the measurement of 18F activity. The method is capable of analyzing Li and O in percentage level as reported in the present analysis of two types of lithium titanate samples. Spectroscopic interference of the elements which can directly or indirectly affect the outcome, were evaluated meticulously. Determination of Ti was carried out using fast neutron activation through the product isotopes like 47Sc, 48Sc, generated via (n,p) nuclear reactions. Fast neutron activation methodology seems to be advantageous for Ti determination over thermal neutron activation, as it offers self validation through different isotopes and multiple gamma lines.

Insight Into Disorder, Stress and Strain of Radiation Damaged Pyrochlores: A Possible Mechanism for the Appearance of Defect Fluorite.

We have examined the irradiation response of a titanate and zirconate pyrochlore—both of which are well studied in the literature individually—in an attempt to define the appearance of defect fluorite in zirconate pyrochlores. To our knowledge this study is unique in that it attempts to discover the mechanism of formation by a comparison of the different systems exposed to the same conditions and then examined via a range of techniques that cover a wide length scale. The conditions of approximately 1 displacement per atom via He2+ ions were used to simulate long term waste storage conditions as outlined by previous results from Ewing in a large enough sample volume to allow for neutron diffraction, as not attempted previously. The titanate sample, used as a baseline comparison since it readily becomes amorphous under these conditions behaved as expected. In contrast, the zirconate sample accumulates tensile stress in the absence of detectable strain. We propose this is analogous to the lanthanide zirconate pyrochlores examined by Simeone et al. where they reported the appearance of defect fluorite diffraction patterns due to a reduction in grain size. Radiation damage and stress results in the grains breaking into even smaller crystallites, thus creating even smaller coherent diffraction domains. An (ErNd)2(ZrTi)2O7 pyrochlore was synthesized to examine which mechanism might dominate, amorphization or stress/strain build up. Although strain was detected in the pristine sample via Synchrotron X-ray diffraction it was not of sufficient quality to perform a full analysis on.

Silver-Doped BaSrTiO₃ Nanocomposite: Synthesis, Characterization, Antibacterial and Photocatalytic Activities.

In this research, strontium titanate (SrTiO₃), barium titanate (BaTiO₃), barium strontium titanate (BaSrTiO₃), and Ag-doped BaSrTiO₃ nanocomposites with different Ag contents were fabricated using the sol-gel chemical route. The prepared samples were characterized by several techniques including scanning electron microscopy (SEM), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDS), differential reflectance spectroscopy (DRS), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), inductively coupled plasma spectroscopy (ICP), and Brunauer-Emmett-Teller (BET) measurement. The EDS results indicated that the synthesized nanoparticles had a cube perovskite-like structure. The EDS and ICP results revealed that Ag was doped into the Ba0.5Sr0.5TiO₃ structure. The SEM and TEM images demonstrated that the particle size of 15 mol% Ag-doped Ba0.5Sr0.5TiO₃ was smaller than that of pure Ba0.5Sr0.5TiO₃ as confirmed by surface area results. The photocatalytic properties of undoped titanate samples and Ag-doped Ba0.5Sr0.5TiO₃ were studied by the photodecomposition of Eosin yellowish (EY) and methylene blue (MB) dyes. The results illustrated that the photodegradation efficiency of the Ag-doped Ba0.5Sr0.5TiO₃ was far higher than the undoped titanate sample, and the optimum Ag doping was 15 mol%. The antibacterial activities of pure Ba0.5Sr0.5TiO₃ and Ag-doped Ba0.5Sr0.5Ti0₃ were studied against Staphylococcus aureus as Gram-positive (+) and Pseudomonas aeruginosa and Escherichia coli as Gram-negative (-) bacteria. In comparison with the bare Ba0.5Sr0.5TiO₃ nanoparticles, the Ag-doped sample showed a significant enhancement in antibacterial activities against both Gram-negative and Gram-positive bacterial strains.

Dependence of the dielectric properties of barium titanate ceramics and a composite based on it on the sintering temperature

In this paper, we compare the structure and dielectric properties of the samples of barium titanate ceramics that have been sintered at temperatures of 1100, 1150, 1200, 1250 and 1350 °C and dielectric characteristics of the samples of barium titanate (80 vol.%) — barium ferrite (20 vol.%). It is shown that only samples sintered at the temperature of 1250 and 1350 °C have polarization sufficient for the existence of the piezoelectric effect. For the same samples, the pyroelectric coefficient and reversal polarization significantly exceed those for samples sintered at lower temperatures. Analysis of the samples structure confirmed the dependence of the dielectric properties of the barium titanate ceramics on the grain size and, as a consequence, on the sintering temperature. Based on the studies carried out, the optimal temperature (1250 °С) for obtaining composite samples of barium titanate (80 vol.%) — barium ferrite (20 vol.%) was selected. The temperature dependence of the dielectric constant for the composite samples based on barium ferrite — barium titanate with a sintering temperature of 1250 °C is similar to the dependence for the BaTiO3 ceramic samples sintered at 1350 °C. At room temperatures, the permittivity of the composite samples is also significantly higher than that of the barium titanate ceramic samples obtained at the same sintering temperatures. The addition of barium ferrite to the barium titanate not only increased the permittivity of the composite, but also led to a diffusing of the ferroelectric phase transition and a shift in the temperature of the maximum of the dielectric constant by 10 degrees towards high temperatures.

Low-temperature synthesis of bismuth titanate by modified citrate amorphous method

Bismuth titanate is a lead-free piezoelectric ceramic with outstanding properties that strictly depend on the composition and microstructure. However, bismuth-based materials are difficult to synthesize due to bismuth volatilisation that causes secondary phases and stoichiometry deviations. In this work, we propose a low-temperature chemical route, i.e. a modified amorphous citrate method, that allows a reduction of thermal treatment temperature, when compared with solid-state or other chemical routes, to obtain single-phase bismuth titanate samples. Single-phase powders with particle size under 300 nm are produced by calcination at 700 °C, and prepared into homogeneous dense pellets (density above 95%), with only isolated pores. The pellets show two distinctive features in the electrical behaviours directly associated with their mica-like microstructure: planar oriented boundaries are responsible for oxygen conduction, while the bulk is dominated by electronic conductivity. The samples show a high dielectric constant, around 200 at room temperature, while maintaining a low loss factor. The pellets also achieved a maximum polarisation of 5.85 μC/cm2 and an inverse piezoelectric coefficient of 7.4 pm/V. The dielectric and piezoelectric properties obtained are comparable or superior to the state-of-the-art.

Effect of sintering temperature on dielectric properties of barium titanate ceramics and composite

The structure and dielectric properties of barium titanate ceramics samples sintered at 1100, 1150, 1200, 1250 and 1350 °C have been compared with the dielectric properties of 80 vol.% barium titanate + 20 vol.% barium ferrite composite samples sintered at 1150, 1200 and 1250 °C. It has been shown that polarization sufficient for existence of the piezoelectric effect is only achieved in barium titanate samples sintered at 1250 and 1350 °C. Furthermore the pyroelectric coefficient and reversal polarization of these samples are far higher than those of samples sintered at lower temperatures. Analysis of the sample structures has confirmed that the dielectric properties of barium titanate ceramics depend on grain size and therefore on sintering temperature. Based on the experimental results we have selected the optimum sintering temperature for 80 vol.% barium titanate + 20 vol.% barium ferrite composite to be 1250 °С. Further increase in sintering temperature to 1300 °C showed that this composite has a eutectic. The temperature dependence of the permittivity of the barium titanate / barium ferrite composite sintered at 1250 °С is similar to that of BaTiO3 ceramics samples sintered at 1350 °С. The room temperature permittivity of the composite samples also proves to be far higher than that of barium titanate ceramics samples sintered at the same temperatures. Barium ferrite addition to barium titanate increases the permittivity of the composite and also diffuses the ferroelectric phase transition and shifts the permittivity maximum temperature by 10 °C towards higher temperatures.