BaO Content Research Articles

Promotion of CeO2–ZrO2–Al2O3 composite by selective doping with barium and its supported Pd-only three-way catalyst

In this work, CeO2–ZrO2–Al2O3 (CZA) composites promoted by selective doping with Ba were prepared by simple coprecipitation method. The structural characterization results reveal that with small doping amount (≤6wt%), Ba can preferentially combine with Al2O3 and acts as a stabilizer, which could facilitate the formation of more homogeneous CZ solid solutions. When the content of BaO increases to 8wt%, besides the portion combined with Al2O3, the remnant Ba would enter into the lattice of CeO2–ZrO2 to form a ternary CeO2–ZrO2–BaO solid solution, thus further improved oxygen mobility is obtained. However, excessive doping amount (10wt%) brings about self-aggregation of BaO, which seriously deteriorates the structure of the CeO2–ZrO2–Al2O3-BaO composite. The XPS results demonstrate that with optimal doping content of BaO (8wt%), the supported catalyst Pd/CZAB8 possesses highest surface Pd and Ce3+ concentrations, which consequently leads to improved reducibility and catalytic performance. Furthermore, the synergistic effect between CeO2–ZrO2–BaO and BaO–Al2O3 helps improve the thermal stability of Pd/CZAB8. Thus, superior textural, structural, morphological and reduction properties along with enhanced three-way catalytic performance are obtained for aged Pd/CZAB8a.

Optical properties and weakening of elastic moduli with increasing glass transition temperature (T g) in (80–x)TeO2-xBaO-20ZnO glasses

Abstract BaO addition to ternary (80–x)TeO2-20ZnO-xBaO (x = 0–20 mol.%) glasses resulted in a decrease in ultrasonic velocities and independent elastic moduli; this result indicated that the rigidity of the glass network weakened possibly because non-bridging oxygen increased. Thermal analysis results showed that glass transition temperature increased as BaO content increased because of the stabilizing effect of Ba2+ on the glass network. Additional analyses using bulk compression and ring deformation models revealed that the ratio between theoretical bulk modulus and experimental bulk modulus increased; this result indicated that the compression mechanism mainly involved isotropic ring compression. Furthermore, the increase in non-bridging oxygen formation with BaO addition caused a decrease in optical energy gap and an increase in refractive index. An increase in Urbach energy indicated that the degree of disorder in the glass system also increased.

Electrical properties and low temperature sintering of BiAlO3 doped (Ba0.85Ca0.15)(Zr0.1Ti0.9)O3 lead-free piezoelectric ceramics

(1 − x)(Ba0.85Ca0.15)(Zr0.1Ti0.9)O3–xBiAlO3((1 − x)BCZT–xBAO) piezoelectric ceramics were synthesized by a solid-state reaction method. Effects of BAO content on the sintering temperature, phase structure, microstructure and electrical properties of BCZT ceramics were investigated. X-ray diffraction revealed a phase transition from orthorhombic to tetragonal phases at x = 0.3–1.0 mol%. The grain size gradually becomes smaller with increasing the BAO content. It was observed that the introduction of BAO content not only decreased the sintering temperature from 1450 to 1300 °C but also enhanced the electrical properties and temperature stability. The favorable electrical properties (d 33 = 568 pC/N, k p = 0.54, P r = 8.17 µC/cm2, E c = 3.45 kV/cm, e m = 13,298, e r = 3375, tanδ = 0.021, T c = 72 °C and S = 0.06 %) were demonstrated for the BCZT based ceramics sintered at 1300 °C with x = 0.8 mol%. These results indicated that the ceramics sintered at low temperatures was promising for piezoelectric applications.

Ba- and Ti-enriched dark mica from the UHP metasediments of the Seve Nappe Complex, Swedish Caledonides

Abstract We report on the occurrence of peculiar Ba- and Ti-enriched dark mica in metasedimentary rocks that underwent high-pressure metamorphism in the diamond stability field followed by decompression to granulite facies conditions. The mica occurs as well-developed preserved laths in a quartzofeldspathic matrix. The mean concentrations of BaO and TiO2 in the mica are 11.54 and 7.80wt%, respectively. The maximum amounts of these components are 13.38wt% BaO and 8.45wt% TiO2. The mean crystallochemical formula can be expressed as (K0.54Ba0.39Na0.02Ca0.01)Σ0.96(Fe1.37Mg0.85Ti0.50Al0.29Mn0.01Cr0.01)Σ3.03(Si2.59Al1.41)Σ4.00O10(OH1.30O0.66F0.02S0.01)Σ1.99, with oxyannite, oxy-ferrokinoshitalite and siderophyllite as dominating end-members. Based on the petrographical observations, it is proposed that the dark mica was formed at a rather late stage in the evolution of the parental rock, i.e. under granulite facies conditions.

Interaction between Barium Oxide and Barium Containing Chloride Melt

Abstract Thermal analysis was applied to determine the liquidus temperatures in the NaCl–KCl–BaCl2–BaO system, with BaO concentration varied from 0 to 6 mole%. The temperature dependence of the BaO solubility in the NaCl–KCl–BaCl2 eutectic melt was investigated; the thermodynamic parameters of BaO dissolution were calculated. The caloric effects of melting of the NaCl–KCl–BaCl2 eutectic with barium oxide and barium oxychloride additions were studied. The type, morphology, and composition of oxychloride ionic groupings in the melt were determined in situ using Raman spectroscopy.

Structural, thermal and optical properties of TeO2–ZnO–CdO–BaO glasses doped with VO2+

The glasses with composition 64TeO2–15ZnO–(20−x)CdO–xBaO–1V2O5 (0⩽x⩽20 mol%) were prepared by conventional melt quenching technique. X-ray diffraction analysis was used to confirm the amorphous nature of the glasses. The optical absorption studies revealed that the cut-off wavelength (λα) decreases while optical band gap energy (Eopt) and Urbach energy (ΔE) values increase with an increase of BaO content. Refractive index (n) evaluated from Eopt was found to decrease with an increase of BaO content. The physical parameters such as density (ρ), molar volume (Vm), oxygen packing density (OPD), optical basicity (Λ), molar refraction (Rm), and metallization criterion (M) evaluated and discussed. FTIR and Raman spectroscopic studies showed that the glass network consists of TeO4, TeO3+1/TeO3 and ZnO4 units as basic structural units. The glass transition temperature (Tg) of glass sample, onset crystallization temperature (To) and thermal stability ΔT were determined from Differential Scanning Calorimetry (DSC). Using electron paramagnetic resonance (EPR) spectra of vanadium glasses the spin Hamiltonian parameters and dipolar hyperfine coupling parameters of VO2+ ions were calculated. It was found that V4+ ions in these glasses exist as VO2+ in octahedral coordination with a tetragonal distortion and have C4V symmetry with ground state dxy. Tetragonality (Δg∥/Δg⊥) of vanadium ion sites exhibited non-linear variation with BaO content.

The crystallization and structure features of barium-iron phosphate glasses

The crystallization and structure features of xBaO·(90−x)(60P2O5–40Fe2O3)·10CaF2 glasses, where x=0, 5, 10, 15 and 20mol%, are investigated in details by using X-ray diffraction analysis, Fourier transform infrared spectroscopy, Raman spectroscopy and differential thermal analysis. It is found that the major crystalline phase of barium iron phosphate glasses annealed between 650°C and 850°C is FePO4, and the crystallization is restrained by barium. The predominant infrared absorption band is attributed to the antisymmetric stretching vibrations of (PO3)2− in Q1 units. Raman and Fourier transform infrared spectra reveal that the glasses’ main structural networks are Q1 and Q0 tetrahedrons connected by P–O–P linkages. Moreover, the glass transition temperature increases with BaO content, which suggests that barium can strengthen the thermal stability of the iron phosphate glass.

Development of barium borosilicate glasses for radiation shielding materials using rice husk ash as a silica source

In this work, barium borosilicate glasses produced by using rice husk ash in the compositions xBaO:(80-x)B2O3:20RHA (where x = 30, 35, 40 and 45 wt%) were prepared by melt quenching technique and investigated for their radiation shielding properties. The mass attenuation coefficients, effective atomic numbers and effective electron densities of the glasses were found to increase with the increasing of BaO concentration and the decreasing of gamma rays energy. The glasses in this work exhibited good radiation shielding properties by providing shorter mean free paths (MFP) than all commercial windows; ordinary, hematite and Ilmanite-limonite concretes. The shorter MFP in the glasses with higher BaO in glass matrices reflects the better gamma rays shielding properties. The radiation shielding results and optical transparency of the glasses indicate that the glasses in the present study can be used as radiation shielding materials with higher transparency.

Electrical conductivity and phase transition studies of TiO2-BaO system

The solid solution of BaTiO3 was prepared by conventional solid state reaction. The electrical conductivity of TiO2-BaO system has been studied at different temperatures for various molar ratios. The isothermal conductivity increases with BaO concentration due to the vacancy migration phenomenon. It has been found that the electrical conductivity after attaining a maximum value at 240°C decreases with increase in temperature due to the collapse of the fluorite framework. A second rise in conductivity in the temperature range 470–540°C indicates the phase transition of TiO2 from anatase to rutile. AC Impedance measurements proved that the oxide ion conductivity predominantly arises from the grain contribution. The sample characterization and the study of phase transition changes were done by using XRD, FT-IR and DSC measurements. On increasing the concentration of BaO the transition temperature shifts towards higher side.

The Mould Flux Heat Conduction Performance Designing of High Carbon Steel for Thin Slab Continuous Casting

Heat transfer of the mould flux between the mould and the strand is very complicated, especially for the high carbon steel thin slab continuous casting. In this research the orthogonal experiment has been carried out, and the results showed that: the effect for the heat flux form strong to weak is: R>Na2O>F>MgO>BaO. and in the experiment range, with the R increasing, when the R, Na2O content and the F- content are increasing, the heat flux would be decreasing; with the MgO content increasing, the crystallization temperature would getting fluctuant; with the BaO content increasing, the heat flux would getting fluctuant, when its content is around 6%, the heat flux is reach its summit.

High barium content lead and alkaline-free glasses

Four glass compositions of the system BaO-Al2O3-SiO2 with high content of BaO>50% mol and with B2O3 addition (3–10wt%) were melted at 1400°C. The effect of alkaline earth BaO oxide on the glass phase separation and on refraction index n is investigated. IR and MAS-NMR spectroscopy are used for structural characterization. Finally stable alkaline free glasses with a content of BaO ranging from 47.4Mol.% to 54.5Mol.% and with a n=1.62±0.01at 468.1nm have been obtained.

Features of the production of glasses for claddings of rigid multimode optical fiber

Glasses synthesized on the basis of the R2O-B2O3-SiO2 system, where R2O is Na2O or K2O, have been investigated for the reflective and protective claddings of optical fiber. Laws have been established to describe how the oxides affect the glass-forming capability of optical glasses and their tendency to crystallize in the temperature interval in which optical fiber is drawn and to describe their thermal and optical characteristics. Laws have also been established to describe how the composition and structural factors affect the rheological properties of glasses for the claddings of optical fibers. The optimum concentrations of Al2O3, BaO, and MgO additives have been determined so that their introduction into the composition of the glasses for the light-reflecting cladding ensures that the temperature interval in which the viscosity of the glasses varies from 109 to 104 Pa sec is at least 360°C. The glasses for the light-reflecting and protective claddings are matched with the glass of the light-conducting core with respect to viscosity indices.

The Mould Flux Crystallization Properties Designing of High Carbon Steel for Thin Slab Continuous Casting

Crystallization temperature is very important for the high carbon steel for thin slab continuous casting, in this research the orthogonal experiment has been carried out, and the results showed that: the effect for the flux crystallization temperature form strong to weak is: F>Na2O>R>BaO>MgO. In the experiment range, with the R, Na2O, MgO and F- content increasing, the flux crystallization temperature would be higher, but for the complicated infect of the Na2O and F-, there are some flucuations for the flux crystallization temperature, but for the BaO content increasing, the crystallization temperature of the flux would be decreasing slowly.

Structural correlations in BaO–PbO–B2O3 glasses as inferred from FTIR spectra

Infrared spectra of xBaO·(30-x)PbO·70B2O3, xBaO·(40-x)PbO·60B2O3 and xBaO·(50-x)PbO·50B2O3 glasses have been quantitatively analyzed. The fraction of four coordinated boron atoms varies linearly, for each group, between the values of the corresponding binary borate glasses. The data could be used to calculate and follow the composition dependence of the concentration of structural units in all glasses. The results show a linear increase in the ratio of PbO forming BO4 units to the total content of PbO, with increasing B2O3 in binary PbO–B2O3 glasses. Similar behavior has been observed for the ratio of BaO forming BO4 units to the total content of BaO in binary BaO–B2O3 glasses. The ratio of PbO forming PbO4 units to the total PbO content, and that of BaO forming asymmetric BO3 units to the total BaO content, shows a reversed dependence. The linear change in fraction of four coordinated boron atoms and in density and molar volume suggests that the studied glasses can be treated as mixtures of binary PbO–B2O3 and BaO–B2O3 matrices.

High quantum yield and low concentration quenching of Eu3+ emission in oxyfluoride glass with high BaF2 and Al2O3 contents

New oxyfluoride glasses of 1Eu2O3–50BaF2–xAl2O3–(50−x)B2O3 (x=0–25), yEu2O3–50BaF2–25Al2O3–25B2O3 (y=0–10) (mol), and zEu2O3–1Tb4O7–50BaF2–25Al2O3–25B2O3 (z=0, 0.5) (mol) with a high fluorine content (F/(F+O)=0.4) were synthesized by using a conventional melt-quenching method, and photoluminescence properties such as quantum yield (η), lifetime (τ), and concentration quenching effect of Eu3+ ions were clarified. The glass with 25Al2O3 showed an excellent red luminescence with extremely high quantum yield (η) of 97% in the visible region at the excitation of the wavelength λ=396nm and a long lifetime of τ=3.29ms for the emission (λ=612nm) of Eu3+ ions at the 5D0 level. The effect of concentration quenching in these glasses was also very small, e.g., η=72% even for the glass with 10Eu2O3. The values of η=52% for the green emission of Tb3+ ions and of η=81% for the yellow emission of Eu3+–Tb3+ co-doped ions were also achieved in the glasses. The present study indicates that rare-earth ions of Eu3+ and Tb3+ are dispersed homogeneously in these oxyfluriode glasses and the degree of their its asymmetry (i.e., the electric field gradient) is also widely distributed due to the coordination of both F− and O2− ions. The new oxyfluoride glasses with high BaO and Al2O3 contents have a high potential as hosts for new phosphors with rare-earth ions.

Barium oxide–doped silver phosphate glass

Silver phosphate glasses doped with 0, 5, 10, 15 and 20 wt% BaO were synthesized and characterized. X-ray diffraction studies revealed that the glasses are amorphous in nature. Infrared spectral studies have shown the presence of characteristic P–O–P linkages of linear phosphate chains, presence of O–P–O units in the phosphate tetrahedral and the formation of P–O–Ba bonds in the doped glass. It is also confirmed that, due to doping of BaO, loosening of glassy structure occurred and the glass became more disordered. Differential scanning calorimetric studies revealed that glass transition temperature increased with BaO concentration. Scanning electron microscopy studies showed that BaO doping modifies the microstructures of the glass. Electrical conductivity measurements, between 303 to 373 K, in the frequency range from 0·1 kHz to 10 kHz, have indicated that all glasses are ionic conductors with Ag+ ions as the charge carrier. The electrical conductivities of the doped silver phosphate glass were found to be higher than that of the undoped silver phosphate glass. Results have shown that dielectric constants increased with increase in temperature at all frequencies and decreased with increase of frequency. Decrease in dielectric constants for Ag2O-P2O5 and 20 wt% doped BaO at 373 K are 77 and 85%, respectively, when frequency increased from 0·1 to 0 10 kHz. Dielectric losses in all the glasses decreased with frequency at a particular temperature. It was also found that BaO-doped glass has about 60% more antibacterial property.

Electrical response of bivalent modifier cations into a vanadium–tellurite glassy matrix

In this work, we suggest an explanation of the electrical conductivity behavior of tellurite glassy systems modified with barium when transition metal oxides (V2O5-MoO3) present in the glassy matrix are replaced progressively by barium oxide. These glasses of formula x BaO (1−x) (0.5V2O5·0.5MoO3) 2 TeO2 are obtained by the standard quenching technique and analyzed by means of impedance spectroscopy. We also report some structural results that explain the effect of the bivalent cation (Ba+2) on the electrical response in comparison to the effect of univalent cations on this kind of glassy matrix. The results confirm the existence of a transition from a typical hopping of small polarons response (when the content of BaO is low) to a weak ionic conductive response (when more than 50% of the transition metal oxides content has been replaced by BaO). The independent migration path is suggested by the observed electrical conductivity behavior. In this system, vanadium gives the active centers responsible for the polaron hopping mechanism while barium cations seem to be responsible for the ionic transport regimen.

Raman scattering study of barium borate glasses and melts

Glasses and melts of xBaO–(100−x)B2O3 (x=20, 25, 30, 35, 40, 45, 50, 55, 60 and 67mol%) composition have been prepared and studied using high-temperature Raman spectroscopy. It was shown that the structure of the glassy and molten samples with relatively low concentrations of barium oxide (x=20–35mol%) consists of [B∅4]− charged tetrahedra (∅ is a bridging oxygen atom), B∅2O− asymmetric triangles (O− is a non-bridging oxygen atom) and B∅3 neutral units. The concentration of [B∅4]− tetrahedra (N4) monotonously decreases with increasing BaO content in the melts structure, whereas N4 demonstrates a maximum at x≈40mol% in the glassy samples. B∅O22− pyroborate units appear at x≥40mol%, and BO33− orthoborate anions are also formed in the melts structure when x=60 and 67mol%. The dominant mechanisms for the structural reorganizations generated by changes in temperature depend on the melt composition. The changes in the short range order (SRO) structures can be described by the [B∅4]−⇔B∅2O− isomerization reaction at 25<x<40, whereas the dynamic equilibrium between structural units in the melts with x>50 is most likely described by the 2B∅2O−⇔B∅O22−+B∅3 disproportionation reaction. In both cases, the equilibrium shifts to the right with an increase in temperature. Significant changes in the local structures of melts with a low concentration of barium oxide (x≤20mol%) were not found.

Preparation and near-infrared luminescence properties of Bi2O3-B2O3-BaO glasses

xBi2O3-50B2O3-(50-x)BaO glasses are prepared by melting method. Their infrared luminescence spectra, fluorescence decay curves and Raman scattering spectra are measured. No obvious near-infrared (NIR) luminescence is observed in 50Bi2O3-50B2O3 glass under 808 nm laser diode (LD) pumping. Adding BaO, broadband NIR luminescences are observed in 40Bi2O3-50B2O3-10BaO glass, 45Bi2O3-50B2O3-5BaO glass and 49Bi2O3-50B2O3-1BaO glass. With the increase of BaO concentration, no obvious NIR luminescences are observed in 30Bi2O3-50B2O3-20BaO glass, 20Bi2O3-50B2O3-30BaO glass and 10Bi2O3-50B2O3-40BaO glass. The NIR emissions with several emission peaks appear in 0.5Bi2O3-50B2O3-50BaO glass and 1Bi2O3-50B2O3-50BaO glass. The mechanism for the emission is investigated preliminarily.

Phase evolution and electrical properties of copper-electroded BaTi4O9 materials with BaO–ZnO–B2O3–SiO2 glass system in reducing atmosphere

BaTi4O9 (BT4) microwave dielectric ceramics using a copper electrode and containing 10wt% BaO–ZnO–B2O3–SiO2 (BZBS) glass frit were sintered under reducing atmosphere at 950°C and were investigated on the phase evolutions, microstructures and dielectric properties of BT4 with various BaO/SiO2 and ZnO/SiO2 ratios of BZBS glasses. Experimental results show that the BaO/SiO2 ratio contributes to wettability of glass with BaTi4O9 ceramics, and ZnO/SiO2 ratio determines the densification of BaTi4O9 ceramics. The different Ba–Ti–O and Ba–Cu–O phases with various Ba/Ti and Ba/Cu ratios can be attributed to the contents of BaO in glass. Ba4Ti13O30 and Ba2Cu3O5+X may form when BaO contents are too high, and inducing copper diffusion due to the reactions of BaO and Cu, accompanying with degrading of the dielectric characteristics. If the ZnO contents of BZBS glasses were raised, a little bit of ZnSiO3 and Ba2Cu3O5+X phases appear without Cu diffusion due to non-reaction of ZnO and CuO. The high ZnO/SiO2 ratio of glass reveals the lower softening point, indicating that the high ZnO glass could enhance the density and therefore increase the dielectric constant and quality factor.