Facile Fabrication of Porous Bi2O3 Microspheres by Thermal Treatment of Bi2O2CO3 Microspheres and its Photocatalysis Properties

β- and α-phase porous Bi₂O₃ microspheres with an average size of around 4 μm had been synthesized by thermal treatment of Bi₂O₂CO₃ microspheres at 350 and 400–500 °C respectively in an air atmosphere. The Bi₂O₂CO₃ microspheres had been synthesized at a temperature of 180 °C by a hydrothermal process using Bi(NO₃)₃ as the bismuth source with the assist of citric acid. By combining the results of X-ray powder diffraction, transmission electron microscope, scanning electron microscopy, and UV–Visible absorption spectra, the structural, morphological and optical properties characterization of the products were performed. The photocatalytic activity of the as-prepared α- and β-phase porous Bi₂O₃ microspheres have been tested by degradation of methylene orange under visible light, indicating that porous β-Bi₂O₃ microspheres showed enhanced photocatalytic performance compared to P25 and α-Bi₂O₃ microspheres.     

Electronic structure and chemical bonding in oxygen conductors β-Bi4V2O11 and γ-Bi4V2O11

Ab initio calculations of the electron density are fulfilled for bismuth vanadate polymorphs: β-Bi₄V₂O₁₁ and γ-Bi₄V₂O₁₁. A semiconductor-type spectrum is obtained for both phases. The calculated bandgap value decreases in the direction from the β to γ phase. Chemical bond analysis shows an increase in the strength of covalent interactions in the series of Bi-V, Bi-O, and V-O bonds. The V-O bond strength in β-Bi₄V₂O₁₁ is appreciably higher than in the γ phase. The relatively weak binding of oxygen in the tetragonal structure of γ-Bi₄V₂O₁₁ confirms the possibility of easier oxygen transport in the γ phase than in the β phase. The stability of the bismuth vanadate polymorphs and the oxygen-disorder features in the γ-Bi₄V₂O₁₁ structure are discussed using the results of calculation of the total energies of the phases. Bond overlap population analysis explains the existence of the homogeneous range and the feasibility of doping β-Bi₄V₂O₁₁ and γ-Bi₄V₂O₁₁. The possibility of using four-and five-charged d cations as stabilizers of the crystal structure of bismuth vanadates is discussed.     

Thin Coatings of α- and β-Bi2O3 by Ultrasonic Spray Coating of a Molecular Bismuth Oxido Cluster and their Application for Photocatalytic Water Purification Under Visible Light

Thin coatings of Bi₂O₃ were deposited on glass substrates by ultrasonic spray coating of THF solutions of the molecular precursor [Bi₃₈O₄₅(OMc)₂₄(DMSO)₉] ⋅ 2DMSO ⋅ 7H₂O (OMc=O₂CC₃H₅) followed by hydrolysis and subsequent annealing. Depending on the synthetic protocol, the bismuth oxido cluster was transformed into either α- or β-Bi₂O₃. The as-synthesized Bi₂O₃ coatings were characterized by powder X-ray diffraction (PXRD), thickness measurements, diffuse reflectance UV-Vis spectroscopy (DRS), photoluminescence (PL) spectroscopy, Raman spectroscopy and scanning electron microscopy (SEM). The thin coatings (thickness: 5–16 μm) were compared with regard to their performance in photocatalytic rhodamine B (RhB) decomposition under visible light irradiation. The β-Bi₂O₃ coatings, that showed the highest photocatalytic activity, were used for the photocatalytic decomposition of other pollutants such as triclosan and ethinyl estradiol. In addition, the interplay between the photooxidation that is induced by the excitation of the catalyst using visible light and the photosensitized decomposition pathway was studied by degradation experiments of aqueous rhodamine B solutions using β-Bi₂O₃ coatings.     

Controlled synthesis of bismuth oxo nanoscale crystals (BiOCl, Bi12O17Cl2, α-Bi2O3, and (BiO)2CO3) by solution-phase methods

We present the controlled solution-phase synthesis of several sheet- or rod-like bismuth oxides, BiOCl, Bi₁₂O₁₇Cl₂, α-Bi₂O₃ and (BiO)₂CO₃, by adjusting growth parameters such as reaction temperature, mole ratios of reactants, and the base used. BiOCl, Bi₁₂O₁₇Cl₂, and α-Bi₂O₃ could be prepared from BiCl₃ and NaOH, whereas (BiO)₂CO₃ was prepared from BiCl₃ and urea. BiOCl and Bi₁₂O₁₇Cl₂ could also be prepared from BiCl₃ and ammonia. The α-Bi₂O₃ sample exhibited strong emission at room temperature.     

Investigation par analyse thermique differentielle du systeme Gd2(MoO4)3-Bi2(MoO4)3

The phase diagram of the system Gd₂(MoO₄)₃-Bi(MoO₄)₃ has been studied by differential thermal analysis (DTA). Sealed platinum tubes were used as sample holders, in order to prevent the loss of Bi₂O₃ and MoO₃ through volatilization at high temperature. Various solid solutions and new phases are reported: α-Gd_2-x-Bi_x(MoO₄)₃, β -Gd_2-x-Bi_x(MoO₄)₃, α-Bi_2-xGd_x(MoO₄)₃, 3Gd₂(MoO₄)₃·2Bi₂(MoO₄)₃, etc.     

Synthesis of a new bismuth oxide fluoride with the γ-Bi2O3 structure type

A new bismuth compound with the γ-Bi₂O₃ structure type has been synthesized by a hydrothermal method. The experimental results show that only the solution or starting materials which contain fluorine ions are effectual for the synthesis of the compound. Chemical analysis proved that the new compound contains a small amount of fluorine. We comment the stabilization of the γ-form by partial replacement of oxygen atoms with fluorine atoms and assume Bi₂₆O₃₈F₂ as its constitution. The measured dimension of the unit cell is 10.183(2) Å. Its thermal stability is also studied by differential thermal analysis.     

Crystal-structure refinement, thermal expansion, and chemical distortion of Bi2Ga4O9

Single crystals of Bi₂Ga₄O₉ are grown from a solution in a bismuth oxide melt. The structure (orthorhombic, space group Pbam, a = 7.918(2) Å, b = 8.299(2) Å, c = 5.894(2) Å, Z = 2) is refined to R = 0.052 in the anisotropic approximation based on single-crystal X-ray diffraction data. The structure is a framework. The bismuth(III) atoms are sixfold coordinated; gallium(III) exists in both tetrahedral and octahedral coordinations. The thermal expansion of Bi₂Ga₄O₉ is studied by high-temperature X-ray powder diffraction method and is found to be sharply anisotropic. A structural interpretation of the anisotropy is proposed. Chemical distortion in the Bi₂M₄O₉ compounds with M = Fe(III), Al, or Ga is analyzed and compared with the thermal expansion of Bi₂Ga₄O₉.     

Crystal growth, crystal structure of new polymorphic modification, β-Bi2B8O15 and thermal expansion of α-Bi2B8O15

Single crystals of α- and β-polymorphs of Bi₂B₈O₁₅ were grown by Czochralski method from a charge of the stoichiometric composition. The crystal structure of β-Bi₂B₈O₁₅ was solved by direct methods from a twinned crystal and refined to R1=0.081 (wR=0.198) on the basis of 1584 unique observed reflections (I>2σ(I)). The compound is triclinic, space group , a=4.3159(8), b=6. 4604(12), c=22.485(4) Å, α=87.094(15)°, β=86.538(15)°, γ=74.420(14)°, V=602.40(19) Å³, Z=2. The B-O layered anion of β-Bi₂B₈O₁₅ is topologically identical to the anion of α-Bi₂B₈O₁₅ but the orientation of neighboring layers is different. Thermal expansion of α-Bi₂B₈O₁₅ has been investigated by X-ray powder diffraction in air in temperature range from 20 to 700 °C. It is strongly anisotropic, which can be explained by the hinge mechanism applied to chains of Bi-O polyhedra. While the anisotropy of thermal expansion is rather high, the volume thermal expansion coefficient α_V=40×10⁶ °C⁻¹ for α-Bi₂B₈O₁₅ is close to those of other bismuth borates.     

Sur la Stoechiométrie de la Variété Allotropique γ de Bi2O3

On the Stoichiometry of the Allotropic Variation γ-Bi₂O₃ The study of the solid solutions Bi₁₂[BBi□_1/5]O₂₀ (B^+V = As, V) with 0 ? x ? 0,80 leads for x = 0,77 to a phase whose cubic centered symmetry and parameter (10.255 Å) correspond to those previously announced for γ-Bi₂O₃. The présence of impurities seems required to obtain such a phase whose theoretical stoichiometry should be Bi₁₂[Bi□_1/5]O₂₀ i. e. Bi₂O_3,125.     

Kinetics of photostimulated transformations in nanosized bismuth films

Optical spectroscopy, gravimetric analysis, and microscopy studies show that irradiating bismuth films (d = 3–55 nm) with light (λ = 360 nm and I = 1.8 × 10¹⁵–7.0 × 10¹⁵ quantum cm^?2 s^?1) leads to major changes in their absorption and reflectance spectra and in film mass. The kinetic curves of the degree of photochemical transformation of bismuth films are shown to obey linear, inverse logarithmic, cubic, and logarithmic laws. The contact potential difference (CPD) of Bi and Bi₂O₃ films and the photo-electromotive force (emf) of Bi-Bi₂O₃ systems are measured. An energy band diagram of Bi-Bi₂O₃ systems is constructed. A model that includes the stages of generation, recombination, and redistribution of nonequilibrium charge carriers in the contact field of a Bi-Bi₂O₃ system, oxygen adsorption, diffusion of cation vacancies, and Bi₂O₃ formation is proposed.     

Bi2(IO3)(IO6): First combination of [IO3]− and [IO6]5− anions in three-dimensional framework

A new bismuth (III) iodate periodate, Bi₂(IO₃)(IO₆) was obtained from hydrothermal reactions using Bi(NO₃)₃·5H₂O, and H₅IO₆ as starting materials. Bi₂(IO₃)(IO₆) crystallizes in the monoclinic space group P2₁/c (No. 14) with lattice parameters ɑ = 8.1119(6), b = 5.4746(4), c = 16.357(1) Å, β = 99.187(2)°, V = 717.07(9) ų, Z = 4. The structure of Bi₂(IO₃)(IO₆) features a three-dimensional framework which is a combination of [Bi(1)O₅] tetragonal pyramids, [Bi(2)O₈] bicapped trigonal prisms and [IO₃]⁻ and [IO₆]⁵⁻ anions. Thermal analysis shows that the compound is thermally stable up to about 350 °C. The solid state UV-vis-NIR diffuse reflectance spectrum indicates that Bi₂(IO₃)(IO₆) is a semiconductor with a band gap of 2.76 eV.     

Structural and dynamical studies of δ-Bi2O3 oxide-ion conductors: II. A structural comparison of (Bi2O3)1−x(M2O3)x for M = Y,Er, and Yb

We report the results of diffuse elastic neutron scattering studies of the superionic solid solutions (Bi₂O₃)_1−x(Er₂O₃)_x and (Bi₂O₃)_1−x(Yb₂O₃)_x, and also the result of a Bragg diffraction study of (Bi₂O₃)_0.75(Er₂O₃)_0.25. All the data suggest that Er³⁺-doped δ-Bi₂O₃ is structurally very similar to the fluorite-related solid solution (Bi₂O₃)_1−x(Y₂O₃)_x studied previously, both in terms of the average structure as determined by Bragg scattering and in terms of local ordering on the anion sublattice as detected by diffuse scattering. The ordered regions are described as microdomains of a rhombohedral phase. The Yb³⁺-doped materials also show short-range anion ordering, but over shorter distances than in the other two cases. There is evidence of cation ordering between Bi³⁺ and Yb³⁺ near the low-dopant boundary of the fluorite phase. The possible use of quasi elastic neutron scattering to monitor oxide-ion transport in the system (Bi₂O₃)_1−x(Er₂O₃)_x is discussed.     

A novel route to nanostructured bismuth telluride films by electrodeposition

We report a novel route to the fabrication of 3D nanostructured stoichiometric bismuth telluride (Bi₂Te₃) films by electrodeposition through inverse lipid cubic phases as evidenced by Small-angle X-ray Scattering (SAXS) and Helium Ion Microscopy (HIM). The nanostructured Bi₂Te₃ films were composed of interconnected nanowires with diameters of 60–150 Å.     

TG and DTA study of oxygen depletion and reoxidation of bismuth molybdates (2∶1;2∶3)

Oxygen depletion and reoxidation of bismuth molybdates (2∶1; 2∶3) have been studied by means of isothermal thermogravimetry and DTA measurements. From the isothermal curves, Arrhenius energies were obtained between 411 and 683 K. The activation energies for oxygen depletion from Bi₂O₃·MoO₃ were lower than those for Bi₂O₃·3MoO₃. Two kinetically different types of oxygen release were identified for both molybdates. Arrhenius plots were also obtained from reoxidation experiments: Bi₂O₃·MoO₃ was more easily reoxidable than Bi₂O₃·3MoO₃. The substantial closeness of the respective activation energies suggests that depletion and reoxidation follow the same mechanistic steps. Some DTA measurements confirm the existence of at least two types of reoxidation sites for both oxysalts.     

Thermal,structural and electrical studies of bismuth zinc borate glasses

Bismuth Zinc Borate glasses with compositions xBi₂O₃–30ZnO–(70 − x)B₂O₃ (where x = 30, 35, 40 and 45 mol %) have been prepared by melt quenching method. These glasses were characterized by X-ray diffraction (XRD), Differential Thermal Analysis (DTA), Fourier Transform Infrared Spectrometer (FTIR) and Broad Band Dielectric Spectrometer (BDS). DTA and FTIR analysis reveals that Non-Bridging Oxygens (NBOs) increase with increase of bismuth content in the glass. Electrical data have been analyzed in the framework of impedance and modulus formalisms. The activation energy for dc conductivity decreases with increase of bismuth concentration. The imaginary part of modulus spectra has been fitted to non-exponential Kohlrausch–Williams–Watts (KWW) function and the value of the stretched exponent (β) is found to be almost independent of temperature but slightly dependent on composition.     

Research on the electrochemistry of oxygen ion conductors in the former Soviet Union

Following previous reviews of research results on oxygen ion-conducting materials obtained in the former USSR, this article addresses the case of Bi₂O₃-based compositions. Phase formation in oxide systems with Bi₂O₃, thermal expansion, stability, bulk transport properties and oxygen exchange of bismuth oxide solid electrolytes are briefly discussed. Primary attention is focused on oxides with high ionic and mixed conductivity, including stabilized fluorite-type (δ) and sillenite (γ) phases of Bi₂O₃, γ-Bi₄V₂O₁₁ and other compounds of the aurivillius series. Another major point being addressed is on the applicability of these materials in high-temperature electrochemical cells, which is limited by numerous specific disadvantages of Bi₂O₃-based ceramics. The electrochemical properties of various electrode systems with bismuth oxide electrolytes are also briefly analyzed. Electronic Publication     

Structures and ionic conductivities in two fluorite type families: Pb5Bi17X5O43 and Pb5Bi18X4O42 (X=P,V and As)

The phases Pb₅Bi₁₇P₅O₄₃ and Pb₅Bi₁₈P₄O₄₂ are among many recent new oxyphosphates discovered in the ternary system PbO–Bi₂O₃–P₂O₅. The syntheses of the vanadates and arsenates led to isostructural compounds. Both series display a distorted 3×3×3 superstructure of the tetragonal δ-Bi₂O₃ polymorph. These types of phases display interesting anion conductivities and measurements were performed from 300 °C to 800 °C on the phosphates, arsenates and vanadates of the two families. The Pb₅Bi₁₈X₄O₄₂ phases have higher conductivity values than those of Pb₅Bi₁₇X₅O₄₃. Of the three homologues the vanadates always have the highest conductivities, i.e., at 800 °C: 1.6×10⁻² Siemens·cm⁻¹ for Pb₅Bi₁₈V₄O₄₂ and 1.6×10⁻³ Siemens·cm⁻¹ for Pb₅Bi₁₇V₅O₄₃. An increase of the volume of the unit cell due to the increasing radius of the pentavalent cations from P, As to V, 0.34 Å, 0.47 Å, 0.59 Å respectively, helps the anion migration through the structure.     

Thermal stability of Bi<Subscript>2</Subscript>O<Subscript>3</Subscript>

Differential thermal analysis (DTA) and thermogravimetric analysis (TGA) of an α-Bi₂O₃ sample revealed staged phase transitions in the range 720–800°C (at 720, 780, and 800°C) and the elimination of oxygen to the composition Bi₂O_2.967 during heating to 895°C in air at 16 K/min. In dynamic vacuum (p = 1.33 Pa) at 780–800°C, Bi₂O₃ consecutively transforms to a phase with the cubic γ-Bi₂O₃ structure and tetragonal Bi₂O_2.3?2.4. In the latter, electron diffraction in a transmission electron microscope (ED/TEM) shows a superstructure with the superstructure vector q ₁₁₀ ≈ 1/9, which indicates an ordered arrangement of oxygen vacancies.     

Preparation, characterization and catalytic activity of Bi−Mo-based catalysts for the oxidative dehydrogenation ofn-butene to 1,3-butadiene

Multicomponent bismuth molybdates were prepared by a co-precipitation method for use in the oxidative dehydrogenation ofn-butene to 1,3-butadiene. The effect of divalent and trivalent metals on the catalytic performance of multicomponent bismuth molybdate catalysts was investigated. It was found that the metal ratio of Fe/Bi/Mo=3∶1∶12 was favorable for the reaction. The successful formation of Ni _X Co_8?X Fe₃Bi₁Mo₁₂O₅₀ (X=0?8) catalysts was well confirmed by XRD and ICP-AES measurements. The multicomponent bismuth molybdate catalysts showed a better catalytic performance than the pure γ-Bi₂MoO₆ catalyst. Among the Ni _X Co_8?X Fe₃Bi₁Mo₁₂O₅₀ (X=0?8) catalysts, Ni₃Co₅Fe₃Bi₁Mo₁₂O₅₀ showed the highest yield of 1,3-butadiene.     

BIFEVOX Composites: Manufacture and Characterization

Design of composites is a way to improve the quality of solid electrolytes. By mechanically mixing and annealing substituted bismuth vanadate with nanosized aluminum, bismuth, and zirconium binary oxides, we obtained heterogeneous materials Bi₄V_1.7Fe_0.3O_{11 – δ}/xAl₂O₃, Bi₄V_1.7Fe_0.3O_{11 – δ}/xBi₂O₃, and Bi₄V_1.7Fe_0.3O_{11 – δ}/xYSZ. The investigation tools were X-ray powder diffraction and electron microscopy with energy-dispersive microanalysis. The composition of materials was studied, the non-interaction of components was elucidated in the aluminum oxide and zirconium oxide composite series, and a nonuniform distribution of nanopowder particles across the surfaces and cleaves of sinters was discovered. The bismuth atoms from bismuth oxide were shown to be capable of incorporating into the Bi₄Fe_0.3V_1.7O_{11 – δ} structure. The charge transport characteristics of the materials were studied by impedance spectroscopy. No changes were observed in logσ–10³/T trends in composites with various binary oxides and various oxide contents. An increase in binary oxide concentration was shown to give rise to an insignificant decay in electrical conductivity.