Ba Doping Research Articles

Preparation of Ba-doped SrTiO3 photocatalyst by sol-gel method for hydrogen generation

Increasing energy demands and its impact on the environment make it necessary to look for alternative renewable energy sources. Hydrogen is considered as energy vector but on earth, free hydrogen is not available and found in the compound state. In this study, BaxSr1-xTiO3 (x = 0.00, 0.05, 0.10 and 0.20) photocatalysts are prepared by sol-gel method for water splitting. XRD patterns showed the formation of the pure cubic structure of SrTiO3. It was observed that the optical absorption of SrTiO3 was increased by increasing Ba content. Solar to hydrogen conversion efficiency of SrTiO3 photocatalyst were increased by increasing Ba doping.

Significantly suppressed leakage current and reduced band gap of BiFeO3 through Ba–Zr Co-Substitution: Structural, optical, electrical and magnetic study

Bismuth Ferrite (BFO), Ba substituted BFO (BBFO) and Ba–Zr co-substituted BFO (BBFZO) nanoparticles have been synthesized via citrate-gel route. The common problem of BFO i.e; compositional instability, low magnetization and high leakage current was resolved by this doping technique. Remanent magnetization and remanent polarization improved significantly for BBFZO sample compared to that of BFO. Structural, optical and improved dielectric properties were also investigated. Structural study confirmed the enhanced structural distortion in BFO due to doping of Ba and Ba–Zr ions. The calculated energy band gap has been reduced to 1.52 eV for BBFZO nanoparticles from a value of 2.55 eV for BFO. Leakage current was suppressed by almost seven orders of magnitude for Ba–Zr co-substituted bulk BFO compared to that of undoped BFO. Morphological study of bulk samples has shown gradual reduction in grain size upon Ba doping and Ba–Zr co-doping in BFO, respectively.

Visible-light-induced degradation of Rhodamine B by Ba doped ZnO nanoparticles

In the present work, ZnO and Ba doped ZnO nanoparticles (Ba/ZnO) were synthesized by the sol-gel approach. The effects of Ba doping and calcination temperature on photodegradation of Rhodamine B (RhB) were examined under visible light irradiation. In the optimized synthesis conditions, 0.1% Ba loading, and 400 °C calcination temperature, the photocatalyst revealed considerable activity toward photodegradation of RhB. The photocatalytic process by optimal photocatalyst was further modeled and optimized by Response Surface Methodology. The maximum removal efficiency of 98.40% was obtained for catalyst dosage of 350 mg L−1, initial RhB concentration of 4.11 mg L−1, the irradiation time of 68 min, and pH 8. In addition, for 0.1% Ba/ZnO photocatalyst, the activity under visible light was near to UV-A light with a considerable reduction in photoluminescent spectra (PL) compared to neat ZnO. A comparison of PL spectra of RhB and RhB/0.1%Ba/ZnO showed considerable quenching of the light-emitting broad peak of RhB for the later confirming the photosensitizer effect of adsorbed RhB for efficient visible-light-driven degradation of dye.

Barium‐Doped Zinc Oxide Thin Films as Highly Efficient and Reusable Photocatalysts

AbstractIn this study, the effect of Ba doping content on the photocatalytic activity of (Zn1‐xBaxO (ZBO); x=0 to 0.2) thin films is investigated. The efficiency of ZBO photocatalyst for the decolorization of Rhodamine B (RhB) is found to be optimum at x=0.1. The Zn0.9Ba0.1O film exhibits an efficiency of 96% at an irradiation time of 60 min. The high photocatalytic activity of Ba doped ZnO films is attributed to the high efficient generation and separation of photo‐induced charge carriers as evident from photocurrent measurements. Further, the texture and the oxygen vacancies favor the photocatalytic activity as suggested by the x‐ray diffraction (XRD), scanning electron microscope (SEM), x‐ray photoelectron spectroscopy (XPS), Raman spectroscopy and photoluminescence (PL) analysis. Moreover, the reusability test reveals that the photocatalyst performance remains for at least six consecutive cycles without significant change. The higher efficiency and outstanding reusability of Zn0.9Ba0.1O make it a potential candidate for photocatalytic applications.

Rapid Synthesis and Electric Transport Properties of (Ca1−xBax)12Al14O33 Electrides

Ba-doped electrides (Ca1−xBax)12A7:e− (0 ≤ x ≤ 0.05) bulk was rapidly prepared by high-temperature solid-phase reaction combined with spark plasma sintering, and the preparation time was shortened to about 3 h. The electrical transport properties were tested at room temperature. The results show that Ba doping is beneficial to the optimization of C12A7:e− electric transport properties, where (Ca0.96Ba0.04)12A7:e− samples have the highest conductivity (1145 S/cm) and the highest carrier concentration (2.26 × 1021 cm−3). The carrier concentration increased by nearly one order of magnitude compared to the C12A7:e− sample prepared under the same conditions. The electronic structure of (Ca0.96Ba0.04)12A7:e− and C12A7:e− was calculated by first-principles. The calculation results show that (Ca0.96Ba0.04)12A7:e− is lower than the frame conduction band of C12A7:e−, and the density of states near the Fermi level increases, indicating that Ba doping is beneficial to the optimization of C12A7:e− electric transport performance. The results of first-principles calculation provide theoretical support for the experiment.

Tailoring perovskite surface composition to design efficient lean NOx trap Pd–La1-xAxCoO3/Al2O3-type catalysts (with A = Sr or Ba)

Here we report the influence of surface composition on the NOx removal efficiency of lean NOx trap Pd–La1-xAxCoO3/Al2O3-type catalysts. Three catalysts were prepared by the sequential impregnation of 30 wt.% of La1-xAxCoO3-type perovskites and 1.9 wt.% of Pd over alumina. The following perovskite compositions were used: La0.7Sr0.3CoO3, La0.7Ba0.3CoO3 or La0.5Ba0.5CoO3. The results of X-Ray diffraction, N2 adsorption-desorption at −196 °C, electron microscopy, temperature programmed techniques, and Raman and X-ray photoelectron spectroscopies demonstrated that lanthanum partial substitution by barium promoted the presence of Ba-based phases homogeneously distributed at the surface. This fact together with the higher basicity of Ba than Sr led to an increase of the surface basicity for Ba-doped samples. Likewise, Ba doping also favors the formation of small PdO particles homogenously distributed over the surface in close contact with the perovskite phase. Hence, the interactions between Pd and surface basic sites were also promoted. As a result, 1.9 wt.% Pd–30 wt.% La0.5Ba0.5CoO3/Al2O3 catalyst exhibited the highest NOx adsorption and reduction efficiency. Specifically, the NO global conversion and nitrogen production were as high as 90 % and 72 % at 350 °C, respectively. The enhancement of NOx storage capacity during the lean period is mainly assigned to the displacement of gas/solid equilibrium between NO2 and the available NOx adsorption sites due to the presence of higher concentration of basic sites at the surface. Meanwhile, the promotion of the NOx reduction capacity is due to the higher strength of NOx adsorbed species, which slows down the decomposition rate of NOx adsorbed species. Furthermore, the high proximity of Pd and perovskite phase favors the intermediate compounds diffusion. These results confirmed the excellent NOx removal efficiency of the 30 wt.% La0.5Ba0.5CoO3-based catalyst, even above than Pt-based model catalyst.

Enhanced optical transparency and electrical conductivity of Ba and Sb co-doped SnO2 thin films

The highly conducting Ba and Sb co-doped SnO2 (BATO) thin films have been deposited on the glass substrates by cost-effective spray pyrolysis method. The structural, surface, optical properties of the films are investigated as a function of fixed Sb and varying Ba doping concentrations. X-ray diffraction data indicated the films to be polycrystalline with a tetragonal crystal structure. The 2 wt % Ba and 5 wt % Sb co-doped (BATO2) film showed higher average transmittance of about 85% in the visible region and the estimated direct bandgap value was 3.71 eV. The BATO2 film also showed relatively low resistivity of 4.415 × 10−4 Ω cm and sheet resistance of 23.14 Ω/□ than films of other concentration. A temperature-dependent electrical conductivity measurement was carried out to investigate the conduction mechanism of the films by estimating the activation energies using Arrhenius plots. Temperature-dependent electrical properties of the films are also theoretically verified using Kröger–Vink notation. At the higher temperature region, the electrical properties were analyzed in terms of ionic carrier concentration and oxygen partial pressure. These experimental results indicate that the Ba and Sb co-doped SnO2 thin film is a potential candidate for alternative transparent conducting electrode application.

Promotive effect of Ba doping on redox properties of Mn in Ba-doped LaMnO3 for dehydrogenation of ethane

Promotive effect of Ba doping on redox properties of Mn in Ba-doped LaMnO3 for dehydrogenation of ethane

Structural and Electrical Characterization of Ba/ZnO Nanoparticles Fabricated by Co-precipitation

Ba-doped ZnO nanostructures (0.8–4 mmol) were successfully fabricated by the co-precipitation method. X-ray diffraction analysis indicated that all samples exhibited a typical hexagonal wurtzite ZnO structure with the emergence of BaO phase. Moreover, the incorporation of Ba resulted in an increase of crystallite size and lattice parameter while microstrain decreases. The broadening of the Zn–O vibrational band and the redshift in Raman vibrational modes provided clear evidence of the incorporation of Ba within ZnO host lattice. Furthermore, Ba doping prompted an increase of the dielectric constant and ac conductivity (σac). Additionally, the subsequent decrease in tangent loss with increasing the applied field frequency was associated with the hopping frequency of electron that enhances the charge carriers’ mobility.

Structural and Optical Properties of Sm3+ Doped B-site Ba0.5Rb0.5LaTeO6 Double Perovskites

A double perovskites Ba0.5Rb0.5LaTeO6 and Ba0.5Rb0.5La0.9Sm0.1TeO6 were synthesized by a solid-state reaction method. The structural properties were studied by using the X-Ray powder diffraction (XRD) and fourier transform infrared spectroscopy (FTIR). Structural analysis of XRD based on Rietveld refinement indicates that the Ba0.5Rb0.5LaTeO6 and Ba0.5Rb0.5La0.9Sm0.1TeO6 have cubic symmetry with space group Fm m. The tolerance factor of the sample also decreases with Sm3+ substitution. The value obtained from tolerance factor for Ba0.5Rb0.5LaTeO6 and Ba0.5Rb0.5La0.9Sm0.1TeO6 was 0.994 and 0.982 respectively. The optical properties were studied using the UV visible absorption spectroscopy (UV-vis). The Ba0.5Rb0.5LaTeO6 and Ba0.5Rb0.5La0.9Sm0.1TeO6 was assumed to be indirect band gap and the optical band gap obtained for Ba0.5Rb0.5LaTeO6 and Ba0.5Rb0.5La0.9Sm0.1TeO6 were 4.1 eV and 4.3 eV respectively.

Identification of barium-site substitution of BiFeO3–Bi0.5K0.5TiO3 multiferroic ceramics: X-ray absorption near edge spectroscopy

In this work, the effects of barium substitution on the local structure, dielectric and magnetic properties of the polycrystalline ceramics 0.6BiFeO3–0.4(Bi0.5K0.5)TiO3 (0.6BFO–0.4BKT) system was investigated. A solid-state reaction technique was used to synthesize the materials with barium (Ba) doping of 1, 3, 5, 7, and 10 mol%. XRD analysis reveals the coexistence between tetragonal and rhombohedral phases of single-phase perovskite in pure 0.6BFO–0.4BKT and the rhombohedral reach phase was found with increasing Ba content. XANES simulations indicate that the majority of Ba atoms occupy A-site in BKT lattice of Ba-doped 0.6BFO-0.4BKT, the oxidation state of Fe, Ti, and Ba ions are +3, +4 and+2, respectively. At 5 mol% of Ba doping content, the dielectric measurement shows the morphotropic phase boundary (MPB) and the maximum value of ferromagnetic characteristic were observed, indicating an optimum composition, properties and production conditions.

Facile fabrication of novel Ba-doped g-C3N4 photocatalyst with remarkably enhanced photocatalytic activity towards tetracycline elimination under visible-light irradiation

A novel photocatalyst, Ba-doped graphitic carbon nitride (g-C3N4), was synthesized via a facial thermal condensation method. Ba at a loading of 2% revealed the highest photocatalytic degradation efficiency of tetracycline (TC) (91.94%) after 120 min of visible light irradiation at an optimal pH of 10. An overall synergy of 69.26% was observed in the case of Ba (2%)-doped g-C3N4 over pure g-C3N4. The remarkable improvement in the TC degradation performance is due to the narrower band-gap energy, the larger surface areas and the lower recombination rate of charge carriers detected through photoluminescence (PL) quenching, suggesting the multiple roles of the Ba doping. The synthesized novel photocatalyst displayed extremely high stability after 5 cycles as confirmed through various characterization techniques. The intermediates generated during the photocatalytic reaction were also detected through liquid chromatography–mass spectrometry (LC-MS) analysis and used to predict the degradation pathway of TC. Photoelectrochemical (PEC) measurements combined with photocatalytic performance obviously demonstrated that Ba doping effectively enhanced the separation of charge carriers and decreased the electron/hole recombination in the g-C3N4 structure.

A novel piezoelectric ceramic with high Curie temperature and high piezoelectric coefficient

0.02Pb(Sb1/2Nb1/2)O3-0.98Pb1-xBax(Zr0.53Ti0.47)O3 (PSN-PBxZT) ceramics with high Curie temperature and high piezoelectric properties were prepared by traditional solid state reaction measurement to meet the requirements for high temperature applications, and the crystal structure, dielectric, piezoelectric and ferroelectric properties were investigated. All the samples show a tetragonal crystal structure at room temperature and there was no noticeable change with the increasing of Ba2+ content. Doping of Ba2+ markedly improved piezoelectric properties of PSN-PZT, the maximum d33~560 pC/N, Tc ~317 °C at x = 0.05. Their outstanding piezoelectric properties will drive the development of high temperature industrial applications.

Ba and Mg co-doping to suppress high-temperature dielectric loss in lead-free Na0.5Bi0.5TiO3-based systems

In this study, Ba, Mg co-doped BNT-based ferroelectric ceramic (Ba0.2Na0.3Bi0.5)Ti0.9Mg0.1O3 is fabricated by conventional solid-state reaction to obtain high-temperature dielectric performance. The temperature dependent dielectric constant and dielectric loss are investigated to understand the high-temperature dielectric behavior of the ceramic. The results show that Ba, Mg co-doped BNT ceramic has a very low dielectric loss (about 0.006–0.023) in a wide temperature range of 200–400 °C with dielectric constant about 3200–3800. The complex impedance plots, temperature dependent conductivity and first principle results reveal that the low dielectric loss at high-temperature is mainly due to the Ba doping increases the migration barrier energy of oxygen ions in BNT. The oxygen ion conduction of BNT-based ceramics is restrained, so that the dielectric loss reduces significantly. The study provides a new BNT-based material with low dielectric loss and temperature- stable dielectric constant in a wide temperature range which has great value of high-temperature applications.

Effects of Ba doping on the structural and electronic properties of La[formula omitted]BaxCuO4

The structural and electronic properties of La2−xBaxCuO4 were investigated as a function of Ba-concentration 0 ≤ x ≤ 1.2, within the virtual crystal approximation (VCA) by means of first-principles total-energy calculations. We found Ba doping induces a quasi-rigid displacement of Cu dx2−y2 and dz2 bands toward higher energies. This effect generates important changes in the Fermi surface topology, which manage to imitate the ARPES momentum distribution map (MDM) measurements and tight-binding calculations recently reported for doped La-based cuprates. The calculations exhibit the significant increase in the contribution of Cu dz2 states at the Fermi level for greater Ba doping content to 0.3, which has effects on orbital hybridisation with Cu dx2−y2 states and therefore in the suppression of the superconducting state. For this Ba doping range, no ferromagnetism was found.

Alkaline-earth elements (Ca, Sr and Ba) doped LaFeO3-δ cathodes for CO2 electroreduction

Alkaline-earth elements (Ca, Sr and Ba) doped LaFeO3-δ-based perovskite oxides are systematically studied to understand how these alkaline-earth elements influence the performance of the parent LaFeO3-δ for CO2 electroreduction. Their crystalline structure, phase stability, sintering property, oxygen desorption, CO2 adsorption, oxygen vacancies and the electron density of Fe cations are studied. Their electrochemical performance for CO2 reduction is evaluated at 800 °C. Distribution of relaxation time analysis of the impedance spectra is conducted to deeply investigate the electrochemical processes occurring on these perovskite cathodes. Our results show that alkaline-earth elements doping improves oxygen desorption and CO2 adsorption ability without phase structure changes. Meanwhile, the oxygen vacancies and the electrons density of Fe under electroreduction conditions are increased by doping alkaline-earth elements. These changes promote the electrochemical processes of CO2 electroreduction. Ca doping leads to performance decaying quickly under high voltages, while Ba doping increases the interface resistance due to the formation of carbonates. Sr is the best choice among the three alkaline-earth elements. The optimal doping amount of Sr is 20% in the La-site. Excessive Sr doping results in the formation of carbonates on the surface, thus hindering the charge transfer and decreasing the number of active sites.

Frequency dependent dielectric relaxation of Ba-doped BiFeO3 nanoparticles

In this work, dielectric properties of barium doped bismuth ferrite (BFO) nanoparticles [Bi1-xBaxFeO3 (x = 0.005–0.025)] synthesized by hydrothermal method are investigated. X-ray diffractograms of pure and doped samples compared with rhombohedral R3c structure without the trace of any impurity phase. The average grain size of doped nanoparticles decreases with increase of Ba content. All the samples exhibited broad absorption in the region extending from 200–650 nm. The optical bandgap of doped samples reduces with an increase of Ba content and a significant reduction in bandgap is observed for 1.5% and 2.5% doping. Samples Bi1-xBaxFeO3 (x = 0.0 and 0.015) exhibits anomalous dielectric response attributed to difference in frequency dependence relaxation of charge carriers within the grain and grain boundaries. The grain (Rg) and grain boundary (Rgb) resistances of these samples are evaluated by fitting the measured complex impedance data with an equivalent circuit. The dielectric constant of Bi1-xBaxFeO3 (x = 0.015) is higher than that of pure BFO in the frequency range of 100 Hz–1 kHz. This is attributed to smaller grains and higher density of defects like oxygen vacancies leading to large space charge polarization. However, at higher frequencies (>1 kHz), the dielectric constant of pure BFO is higher than that of Bi1-xBaxFeO3 (x = 0.015) and hence high dielectric loss. Besides, 1.5% Ba doping has made the ions rigid, which shifts the relaxation peak of tanδ to lower frequency side and reduces the leakage current.

Structural stability of SrZrO3 perovskite and improvement in electronic and optical properties by Ca and Ba doping for optoelectronic applications: a DFT approach

ABSTRACTA detailed theoretical study, based on density functional theory (DFT) with GGA-PBE, of electronic, optical and structural properties of calcium (Ca) and barium (Ba)-doped SrZrO3, is presented. The doping influence on the electronic structure and consequently optical properties are analysed and explained with TDOS and PDOS. Structural parameters vary by partial replacement of strontium (Sr) atom with Ca and Ba in SrZrO3, separately, and PDOS modify themselves with the development of new states at symmetry points and as a result reduction in the electronic band gap is observed. We have also noticed that the indirect band gap of pure SrZrO3 is altered to the direct band gap after doping. The optical properties of the pure and doped SrZrO3 are interrelated with their electronic determinations. The considerable change in the band structure and optical properties by doping of Ca and Ba assert that the doped material is a more attractive contestant for optoelectronic device applications as compared to pure SrZrO3.

Enhanced moisture stability of MAPbI3 perovskite solar cells through Barium doping

Rapid growth within performance and stability of organic-inorganic halide-based perovskite solar cells (PSCs) has made this emerging photovoltaics a great potential for further research towards successful commercialization. However, two major issues of: (i) Structural ambient stability, and (ii) Toxicity, caused by the presence of Pb content, are the pivotal obstacles for the commercialization of environmental friendly PSC. In this regard, we are introducing a highly ambient stable PSC through the incorporation of barium (Ba) with successful ultrashort annealing through intense pulsed light (IPL). The ambient stability of Ba doped perovskite thin films was explored in the humidity range of 35–68%. The power conversion efficiency (PCE) of fabricated devices were found to be 8.99, 7.39, 6.94, 6.60, 5.98 and 3.82% for pristine, 1, 2, 5, 10, and 20 mol% Ba doping, respectively. Afterwards, fabricated devices were kept in ambient environment under dark for 20 days. With systematic photovoltaic analysis, it was observed that the 2.0 mol% Ba doped PSC exhibited 8.0% efficiency drop (from 6.94 to 6.38%), whereas the PCE of pristine based devices decreased from 8.99 to 2.60%, demonstrating an almost 71.0% drop. Our photovoltaic results demonstrated a great improvement within the ambient stability of PSC without any encapsulation which can indicate Ba doping as highly promising approach for the fabrication of PSC with higher ambient stability.

Relaxor behavior and tunable property of lead-free Li+-doped Ba0.9Ca0.1Zr0.2Ti0.8O3 ceramics

Li+ doped lead-free Ba0.9Ca0.1Zr0.2Ti0.8O3 (abbreviated as BCZTL) ceramics were prepared through solid-state reaction method. Effects of Li+ on the formation of oxygen vacancies, change of lattice parameters and grain sizes were investigated. The disordered distribution of Li+ ions on B sites of BCZTL were found to give rise to the emergence of local random fields and facilitate the appearence of polar nanoregions (PNRs), which led to the relaxor behavior observed in dielectric measurements. The physical mechanisms for the influences of Li+ substitution and sintered temperature on the variation of PNRs, relaxor behavior and tunability were also proposed. Compared with other sintered temperatures, the 1300 °C sintered BCZTL sample exhibited relatively lower degree of relaxor behavior (γ = 1.89) and higher tunability (k = 56%) owning to the smaller PNRs size.