O3 Complex Research Articles

Investigation of Sr-substituted Ba1-xSrx(Zn1/3Nb2/3)O3 complex perovskites: Structural, electrical and electrochemical properties

Herein we report the structural, dielectric and electrochemical properties of Ba1-xSrx(Zn1/3Nb2/3)O3 (BSZN, 0 ≤ x ≤ 1) solid solution synthesised by solid-state reaction. A complete substitutional solid solution was obtained, wherein the BSZN cubic perovskites of the space group of Pm3‾m were obtained at x ≤ 0.6 while the pseudo-cubic phases were discernible at x > 0.6. The nano-sized crystallites, as determined by both Scherrer and Williamson-Hall analyses, supported the claim of large polyhedral grains of 0.1–0.3 μm by FE-SEM. Both ε′ and tan δ were found to vary consistently with increasing dopant concentration, except for an anomalous observation for the composition, x = 0.6 with the lowest tan δ of 0.0783 and the highest ε′ of 27.5. Such phenomenon could be attributed to the combined effects of larger grain size, higher relative density and stronger polarisation per molar volume. The impedance analysis revealed that these BSZN perovskites were of the negative temperature coefficient of resistance (NTCR) type. The combined plots of imaginary modulus (M″) and impedance (Z″) against frequency showed the short-range movement of localised charge carriers, suggesting a non-Debye-type relaxation process.

Evolution Characteristics and Typical Pollution Episodes of PM2.5 and O3 Complex Pollution in Bozhou City from 2017 to 2022

In China, atmospheric pollution exhibits a complex pattern, with simultaneous exceedances of fine particulate matter （PM2.5） and ozone （O3） levels becoming evident. To understand the complex pollution characteristics and evolution patterns of PM2.5 and O3 in Bozhou City, various methods such as weather classification, analysis of typical pollution processes, and investigation of precursor sources were employed to explore the pollution and variations of PM2.5 and O3 in Bozhou City from 2017 to 2022 and subsequently analyze their causes and precursor sources. The results indicated that： ① PM2.5-O3 complex pollution in Bozhou City mostly occurred under high-pressure weather conditions, with daytime high temperatures and low humidity promoting the formation of O3 pollution, whereas nighttime high humidity and atmospheric oxidative conditions promoted the generation of secondary components such as nitrates and ammonium salts in PM2.5. ② During the pollution process, PM2.5 in Bozhou City mainly originated from biomass burning, secondary generation, traffic pollution, coal combustion, and dust sources. Volatile organic compounds （VOCs） primarily emerged from plant sources, traffic pollution, oil and gas evaporation, solvent use, fossil fuel combustion, residential emissions, and industrial emissions. Biomass burning and traffic pollution made significant contributions to the pollution process. ③ Analysis of air mass trajectories and regional pollution situations indicated that the overlay of northern and southern air masses, along with local generation, were the main causes of the PM2.5-O3 complex pollution in Bozhou from October 18th to 27th, 2022.

Causes Investigation of PM2.5 and O3 Complex Pollution in a Typical Coastal City in the Bohai Bay Region of China in Autumn: Based on One-Month Continuous Intensive Observation and Model Simulation

In order to investigate the causes of complex air pollution in coastal cities in the Bohai Rim of China, a one-month intensive field observation combined with model simulation was carried out in a typical city named Dongying in September 2022. The results showed that two PM2.5 and O3 complex pollution episodes occurred in Dongying in the observation period, with the primary pollutant being O3. Atmospheric photochemical reactions occurring under unfavorable meteorological conditions led to the production of O3 while at the same time facilitating the generation of nitrate, sulfate, and other secondary components of PM2.5 by enhancing the atmospheric oxidizing capacity, which promoted the formation of complex air pollution. It was worth noting that in the context of high pollutants emission, the occurrence of complex air pollution was more sensitive to the variation in meteorological conditions than to the change in pollutants emission. To continuously improve air quality and protect human health in Dongying, it is recommended that an effective regional joint air pollution prevention and control mechanism with neighboring cities should be established in the premise of effective local pollutants reduction, and special attention should be paid to the adverse effect of the air mass transportation from Bohai Bay.

Influence of Oxygen Nonstoichiometry on the Structural Stability of La1–xCaxMn0.5Co0.5O3 Complex Oxides (x = 0.2–0.6) Subjected to Heat Treatment in He

Influence of Oxygen Nonstoichiometry on the Structural Stability of La1–xCaxMn0.5Co0.5O3 Complex Oxides (x = 0.2–0.6) Subjected to Heat Treatment in He

Fabrication and physical characteristics of K/W double doped BiFeO3 complex electro-ceramic; (Bi1/2K1/2)(Fe1/2W1/2)O3

The main objective of this research work is to investigate the effect of the inclusion of potassium/tungsten (K/W) (at the Bi/Fe site) on the structural, dielectric, electrical, and optical characteristics of eco-friendly BiFeO3 to assess its potential use for multifunctional applications including energy storage. The standard solid-state reaction method was used to synthesize the desired (Bi1/2K1/2)(Fe1/2W1/2)O3 complex compound. Examination of X-ray diffraction data demonstrates the structural transformation of bismuth ferrite from rhombohedral to monoclinic on the addition of K/W. The estimated crystallite size is 52 nm. The standard cell parameters include a = 12.1967 Å, b = 9.0468 Å, c = 6.4971 Å, and β = 105.02°, resulting in a cell volume of 692.40 Å3. Analysis of Raman spectra reveals a slight alteration in intensity and displacement of Raman mode positions, attributed to the doping effect, which confirms the incorporation of K and W ions into the BiFeO3 lattice. Scanning electron microscopy provides an image indicating the dense surface structure of the sample. Elemental analysis through energy-dispersive X-ray spectroscopy verifies the presence and purity of the constituent elements. The material doped with potassium and tungsten exhibits a high dielectric constant (εr ∼ 3 × 103) and low tangent loss (tanδ ∼1). The extensive dielectric studies conducted across various frequencies and temperatures suggest that the sample possesses capacitive properties. The depression angle of 8.51° reflects the extent of deviation from Debye's behavior. The presence of hysteresis loops indicates the presence of ferroelectric behavior.

Multifunctional behavior of solid-state derived Ca-doped BaFe0.5Nb0.5O3 complex perovskite system

In recent years, BaFe0.5Nb0.5O3 (BFN) complex perovskite has been projected as one of the promising Pb-free materials for energy storage applications. The primary goal of this research work is to look into the impact of Ca on the structural, electrical, and magnetic behavior of BFN and examine its suitability for multifunctional applications. The conventional solid-state reaction route is followed to prepare the desired Ba0.88Ca0.12Fe0.5Nb0.5O3 complex perovskite sample. The analysis of X-ray diffraction data reveals that the sample crystallizes in monoclinic symmetry and belongs to the C1m1 space group. The micrograph obtained through scanning electron microscopy indicates the dense surface morphology of the sample. The elemental examination through energy-dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy confirms the purity and reveals information regarding the chemical states of the involved elements. The complex impedance and dielectric studies conducted over a wide frequency and temperature range infer that the sample possesses semiconducting as well as capacitive properties. The magnetic response monitored at room temperature confirms the ferromagnetic behavior of the sample. Based on all the investigations carried out, it can be stated that the synthesized complex perovskite can be used for fabricating tunable microwave devices, energy storage devices, magnetic storage devices, etc.

Effect of zinc on structural, dielectric, ferroelectric, and optical properties of Ba(Fe1/2V1/2)O3 complex perovskite ceramic

The synthesis and characterization (structure, dielectric, electrical, and optical properties) of Ba1-xZnx(Fe1/2V1/2)O3(x = 0,0.05,0.10,0.15) have been reported in this paper. The development of a single-phase orthorhombic structure has been confirmed by analyzing room temperature X-rays diffraction (XRD) patterns/data. The crystallite size decreases with an increase in the concentration of Zn2+. Different vibration modes are confirmed from Raman Spectroscopy. Analysis of FESEM microstructure confirms the reduction in average grain size with increased Zn2+ concentration. Some electrical parameters (dielectric constant, conductivity, and impedance) have provided valuable data on the conduction mechanism, structure-properties relationship, etc. The non-Debye relaxation is confirmed from the Nyquist plot. It also ensures the grain boundary and the bulk effect of the materials. The coercive field and efficiency are maximum (7.419 kV/cm, 60.83%) for the higher concentration of Zn2+(x = 0.15). The direct band gap varies from 3.28 to 3.10 eV with increasing Zn2+ concentration. It confirms the generation of more free electrons in the conduction band and high conductivity.

Relaxation dynamics and hopping mechanism in Mg-doped BaFe0.5Nb0.5O3 complex perovskite

Relaxation dynamics and hopping mechanism in Mg-doped BaFe0.5Nb0.5O3 complex perovskite

Stabilizing the Homopolycation (I4 )2+ with a Hexasulfate in (I4 )[S6 O19 ] and a Borosulfate in (I4 )[B(S2 O7 )2 ]2.

The reaction of elemental iodine and SO3 in a sealed glass ampoule yielded a turquoise-colored solution. At temperatures below 7 °C, deep red crystals of (I4 )[S6 O19 ] grow. With the addition of B2 O3 and pyridine-SO3 complex red crystals of (I4 )[B(S2 O7 )2 ]2 can be obtained after heating the mixture to 120 °C. The combination of an (I4 )2+ cation with oxoanions has previously not been observed. Both anions have a significant but different influence on the structural properties of the (I4 )2+ cation.

Dielectric and impedance study of ‘Ca’-doped BaFe0.5Nb0.5O3 complex perovskite

Dielectric and impedance study of ‘Ca’-doped BaFe0.5Nb0.5O3 complex perovskite

Geometrical Polarization Approach method applied to A(B’B″)O3 complex perovskites

The geometric polarization approach (GPA) method is proposed to obtain the intrinsic polarization of polar dielectrics with complex A(B’B″)O3 perovskite structure. The aspects related to the aliovalent site occupation (B′,B″) in this kind of complex perovskites are presented, discussed and analyzed aiming at its application in GPA. The GPA method is applied to determine the intrinsic polarization of Pb(Zr0.6Ti0.4)O3 (PZT60/40, rhombohedral, R3m space group) and Pb(Zr0.4Ti0.6)O3 (PZT40/60, tetragonal, P4mm) compounds at room temperature as prototype phases of polar dielectrics with complex A(B’B″)O3 perovskite structure. The intrinsic polarizations, 49 μC/cm2 and 45 μC/cm2 for PZT60/40 and PZT40/60 compounds, respectively, as signatures of the polar state and in complete agreement with previous reports, are obtained from the off-centering position of the total negative and positive electric charges at the unit cell.

Dielectric and optical modulation in Ca-doped BFN perovskite for possible device applications

This communication reports the dielectric, conductivity, and optical characteristics of Ba0.96Ca0.04Fe0.5Nb0.5O3 complex perovskite prepared through solid solution route technique. The detailed dielectric study is carried out by analyzing real (ε') and imaginary (ε'') components of complex dielectric constant. Room temperature dielectric behavior indicates that the material can be used for fabricating energy storage devices. Conductivity analysis reveals that the basic conduction in the material is due to the hopping of charge carriers and transport of oxygen vacancies. The optical sensitivity and bandgap are evaluated through UV–Visible spectroscopy.

A+1Nb5+O3 (A = Li, Na, K) Perovskites with Different Fine Structures for Oxidative Coupling of Methane: Tracing the Crystalline Phase Effect on the Surface Active Sites

Targeting to unravel the catalytic sites of some specific perovskites for OCM reaction, and elucidate the influences of crystal phase changes on the active sites, three A+1Nb5+O3 (A = Li, Na, K) complex oxides were synthesized in the pure phase. The reaction performance is ranked as NaNbO3 > KNbO3 > LiNbO3 for the catalysts. It is revealed that LiNbO3 possesses a hexagonal ilmenite-type phase, and NaNbO3 and KNbO3 possess orthorhombic and tetragonal perovskite phases, respectively. Due to the fine structure difference, NaNbO3 and KNbO3 have higher oxygen mobility than LiNbO3, as testified by the electric conductivity measurements. Moreover, the Nb–O bond strength of NaNbO3 and KNbO3 is much weaker than that of LiNbO3, which promotes also the oxygen mobility and phase transformation of the two samples, especially in the high temperature OCM process. As a result, more oxygen vacancies/defects are generated on NaNbO3 and KNbO3, which facilitates the efficient formation of OCM active and selective surface O2– species and basic sites. Subsequently, the OCM performance of NaNbO3 and KNbO3 can be evidently improved. Combining the above advantages, NaNbO3 exhibits the optimal OCM performance in all the samples.

Fabrication and microstructure of preferential orientated 1:1 ordered Ba(Mg1/3Nb2/3)O3 complex perovskite microwave dielectric ceramics by laser floating zone technique

Dense Ba(Mg1/3Nb2/3)O3 complex perovskite ceramics have been successfully fabricated by directional solidification using a laser floating zone (LFZ) technique with various pulling rates. The crystal structure, microstructure, and especially ordering structure are thoroughly investigated by transmission electron microscopy (TEM) and electron backscatter diffraction (EBSD). The LFZ solidified rods are all of the fcc lattice structure with Fm3‾m space group resulting from B-site 1:1 cation ordering in comparison to the hexagonal structure associated with 1:2 ordering prepared by conventional sintering. The 1:1 ordering domains are formed based on the space charge model and separated by anti-phase domain boundaries related to reducing pure translational symmetry upon phase transition. Preferential orientations that <110> directions in the fcc unit cell align along the growth direction (//ND) exist in all the LFZ solidified rods. The slightest deviation is obtained with 75 μm/s pulling rate. The preferential orientated 1:1 ordered ceramics are expected to adopt properties superior to the conventional sintered polycrystalline counterparts.

The ozone-water complex: CCSD(T)/CBS structures and anharmonic vibrational spectroscopy of O3(H2O)n, (n = 1 - 2).

Ozone-water complexes O3(H2O)n (n = 1-2) have been studied using coupled cluster theory with triple excitations CCSD(T) with correlation consistent basis sets aug-cc-pVnZ (n = D, T, Q) and complete basis set (CBS) extrapolation techniques. We identified seven dimer (n = 1) and nine trimer species (n = 2) with open C2v and cyclic D3h ozone. Calculations at the CCSD(T)/CBS level of theory for C2v O3(H2O) on the counterpoise (CP)-corrected potential energy surface yield a dissociation energy of De = 2.31 kcal/mol and an O3 central-oxygen (Oc) H2O oxygen (Ow) distance r[Oc⋯Ow] of 3.097 Å, which is in good agreement with an experimental value of 2.957 Å [J. Z. Gillies et al., J. Mol. Spectrosc. 146, 493 (1991)]. Combining our CCSD(T)/CBS value of De for C2v O3(H2O) with our best estimate anharmonic CCSD(T)/aVTZ ΔZPE yields a Do value of 1.82 kcal/mol; the CCSD(T)/CBS value of De for D3h O3(H2O) is 1.51 kcal/mol and yields an anharmonic CCSD(T)/aVTZ Do = 0.99 kcal/mol. CCSD(T)/aVTZ dissociation energies and structures for C2v O3(H2O)2 are De = 4.15 kcal/mol, (Do = 3.08 kcal/mol) and r[Oc⋯Ow] = 2.973 Å, and De = 2.64 kcal/mol (Do = 1.68 kcal/mol) with r[Oc⋯Ow] = 2.828 Å for D3h O3(H2O)2. The results from ab initio molecular dynamics simulations, which consider dynamic and thermal effects in O3(H2O), show that the O3(H2O) complex remains stable at 50 K and dynamically interconverts between two hydrogen-bonded conformers with short Oc⋯Ow contacts (3.85 Å). Carr-Parrinello molecular dynamic (CPMD) simulations for O3(H2O) and O3(H2O)2 at 100 K demonstrate that O3(H2O)2 remains structurally intact, whereas O3(H2O) dissociates to free ozone and water, a feature consistent with the larger average binding energy in O3(H2O)2 (2.2 kcal/mol) vs that in O3(H2O) (1.8 kcal/mol). Finally, the results from CCSD(T)/CBS and CPMD simulations demonstrate that the large inter-trimer binding energies in O3(H2O)2 would give rise to an elevated trimer/dimer population ratio, making O3(H2O)2 a particularly stable and spectroscopically detectable complex.

Magnetic properties of EuFe0.5Mn0.5O3 complex perovskite

In this study, we determined the crystallographic, magnetization and electrical resistivity properties of a EuFe0.5Mn0.5O3 complex perovskite produced using a combustion synthesis method. The sample crystallized as an orthorhombic perovskite belonging to the Pbnm space group. Magnetization measurements indicated spin reorientation at 206 K and weak ferromagnetic-like ordering at low temperatures. Determining the magnetization as a function of the magnetic field demonstrated the presence of magnetic order, even at room temperature. Resistivity measurements indicated the existence of a small polaron conduction mechanism at high temperature.

Composition-driven phase boundary and electromechanical properties in Bi0.5Na0.5TiO3-A(Mg1/3Nb2/3)O3 binary solid solutions

A(Mg1/3Nb2/3)O3 (abbreviated as AMN, A=Ba, Sr and Ca) complex perovskite with tolerance factor t of 0.937–1.03 was incorporated into Bi0.5Na0.5TiO3 (BNT) matrix with tBNT = 0.977 to form binary solid solutions, and the influence of dopant concentration and type on their ferroelectric and piezoelectric properties were investigated. It is found that the BNT-xCaMN system has a higher driving field, probably due to the co-contribution from smaller A-site ionic radius and larger atomic electronegativity. This study also revealed a relationship between t value of morphotropic and polymorphic phase boundary compositions for the BNT-xAMN systems and AMN end-members with tBaMN = 1.03 > tBNT, tSrMN = 0.972 ≈ tBNT and tCaMN = 0.937 < tBNT, which complements a MPB-t relation for quick predicting the approximate morphotropic and polymorphic phase boundary regions of BNT-based systems.

Magnetite Fe3 O4 Has no Intrinsic Peroxidase Activity, and Is Probably not Involved in Alzheimer's Oxidative Stress.

Despite stated in some highly cited articles, magnetite is devoided of peroxidase activity. In fact, this very stable mixed valence FeII O⋅FeIII2 O3 complex is not catalytically competent to oxidize standard peroxidase substrates, especially at the biologically relevant pH value of 7.4. In addition, magnetite whose deleterious redox activity has been suspected in Alzheimer's disease brain damages, does not significantly interact with amyloid peptide Aβ in vitro, and is not able to induce, either in the presence or absence of Aβ, the reductive activation of dioxygen, the first step of an oxidative stress. In fact, this highly insoluble mineral iron derivative is probably not involved in the oxidative damage of brain neurons of patients with AD.

An insight into the effects of transition metals on the thermal expansion of complex perovskite compounds: an experimental and density functional theory investigation.

ABO3 perovskite-type LaCoO3, LaCo0.5Fe0.5O3, LaCo0.5Ni0.5O3, and LaCo0.5Mn0.5O3 complex oxides were synthesized using the sol-gel method. The microstructure and the thermal expansion behavior of the oxides were investigated. Insights into phonon dispersion and the effects of doped transition metals on thermal expansion were obtained by first-principles calculations based on density functional theory. Thermal expansion coefficients (TECs) at finite temperatures were obtained by quasi harmonic approximation. B-site doping was found to reduce the size of the crystalline grains and the TECs of perovskite compounds. The average TECs of LaCoO3, LaCo0.5Fe0.5O3, LaCo0.5Ni0.5O3, and LaCo0.5Mn0.5O3 were 25 × 10-6 K-1, 11 × 10-6 K-1, 12.5 × 10-6 K-1, and 5 × 10-6 K-1, respectively, in the 0-1000 K temperature range. In addition, the TECs of LaCo0.5Fe0.5O3 and LaCo0.5Ni0.5O3 matched well with those of some common electrolytes.

Etching Induced Stepped Nanostructure on Pb(Mg(1–x/2)Mn(x/2)W1/2)O3 Ceramics

A new solid solution system, Pb(Mg(1–x/2)Mn(x/2)W1/2)O3, is formed by replacing Mg2+ with Mn2+ in the Pb(Mg1/2W1/2)O3 complex perovskite. The solid solution remains in the orthorhombic Pmcn symmetry up to x = 0.1. It is observed that for such a chemical modification, the surface of the grain changes significantly. A stepped surface nanostructure appears in the Mn‐substituted perovskite. Detailed surface morphology of the stepped patterns was revealed by atomic force microscopy (AFM), which determined that the interlayer step height varies from 2.3 to 8.3 nm. Analyse by XRD, SEM, EDX, and AFM suggest that the nature of the stepped surface structure may be the result of etching rather than spiral growth or two‐dimensional nucleation as it was previously believed.