Untersuchungen zum System Bi2O3/BiBr3

Investigation on the System Bi₂O₃/BiBr₃ The temperature functions of decomposition pressures of the ternary compounds on the quasibinary line Bi₂O₃/BiBr₃ were determined by total pressure measurements. The barogram of the system was constructed and the melting diagram precised. The enthalpies of formation and the standard entropies of the solid phases were derived from the decomposition functions (Values see “Inhaltsübersicht”).     

Untersuchungen zum System Bi2O3/BiCl3

Investigation on the System Bi₂O₃/BiCl₃ The temperature functions of decomposition pressures of the ternary compounds on the quasibinary line Bi₂O₃/BiCl₃ were determined by total pressure measurements and mass spectroscopy. The barogram of the system was constructed and the melting diagram precised. The enthalpies of formation and the standard entropies of the solid phases were derived from the decomposition functions: (Values see Inhaltsübersicht).     

Die Existenz einer Gasphasenspezies BiSeO3I und das Verhalten bei Chemischen Transportreaktionen

The Existence of a Gaseous Species BiSeO₃I and the Behaviour at Chemical Vapour Transports The existence of gaseous species BiSeO₃I follows from chemical vapour transport experiments of BiOI_s with SeO_{2, g} as well as Bi₂SeO_{5, s} with BiI_{3, g} and SeO_{2, g} and Bi₂Se₃O_{9, s} witht BiI_{3, g}. The Enthalpy of formation and the Standardentropy were derived from the quantitative transport rates and the standard data of the solid state and gaseous phases.     

Kinetics of the decomposition of calcium carbonate in the presence of Bi2O3

Former studies concerning the formation of the compounds in the pseudobinary systems of Bi₂O₃-MO type (M =Ca, Sr, Ca+Sr) have shown that the reaction which occurs with the highest rate is that between Bi₂O₃ and CaO. In the present work CaCO₃ was used as CaO source. We carried out an investigation of the thermal decomposition of CaCO₃ in the presence of Bi₂O₃ in comparison with the decomposition of pure CaCO₃.The presence of Bi₂O₃ exerts a complex influence on the CaCO₃ decomposition acting on the nucleation as well as on the diffusion of CO₂. The decomposition of the samples with low Bi₂O₃ content follows the mechanism of a contracting sphere. A change from surface nucleation to bulk nucleation is recorded for higher amounts of Bi₂O₃.     

Untersuchungen zum quasibinären System Bi2Se3/BiI3

Investigations on the Pseudobinary System Bi₂Se₃/BiI₃ The phase diagram of the pseudobinary system Bi₂Se₃/BiI₃ was investigated by DTA, total pressure measurements and x-ray phase analysis. Only BiSeI exist as a ternary phase in this system. The compound melts incongruently at 545 °C. Heat of formation and standard entropy were calculated from vapor pressure data.ΔH_B° (BiSeI, f, 298) = (–23.4 ± 1.9) kcal/mol S°(BiSeI, f, 298) = (38.7 ± 3.5) cal/K · mol     

Preparation and crystal structure of [Bi3I(C4H8O3H2)2(C4H8O3H)5]2Bi8I30 containing the novel polynuclear [Bi8I30] anion

Preparation and crystal structure of the novel compound [Bi₃I(C₄H₈O₃H₂)₂(C₄H₈O₃H)₅]₂Bi₈I₃₀ are reported. The title compound is prepared by heating of BiI₃ and diethylene glycol at 413 K in a sealed quartz glass tube filled with argon. Deep red single crystals are grown and applied to perform X-ray powder diffraction and X-ray single-crystal diffraction measurements. The compound crystallizes triclinic with space group P-1: Z=2, a=13.217(1) Å, b=15.277(1) Å, c=22.498(1) Å, α=84.33(1), β=73.18(1), γ=67.48(1). [Bi₃I(C₄H₈O₃H₂)₂(C₄H₈O₃H)₅]₂Bi₈I₃₀ comprises the novel polynuclear [Bi₈I₃₀]⁶⁻ anion and [Bi₃I(C₄H₈O₃H₂)₂(C₄H₈O₃H)₅]³⁺ as the cation. Cation as well as the anion can be assumed to represent intermediates between solid BiI₃ and BiI₃ completely dissolved in diethylene glycol.     

Syntheses and Crystal Structures of the Thallium(I) Iodobismuthates(III) Tl7Bi3I16 and Tl3BiI6

Dark grey (dark red with transmitting light) crystals of heptathallium(I) hexadecaiodo‐tribismuthate(III), Tl₇Bi₃I₁₆, were obtained by slow cooling of a melt from 800 K to ambient temperature and, with higher crystal quality via solvothermal synthesis in aqueous HI by slowly cooling from 428 to 363 K. The compound is diamagnetic and melts congruently at 630(5) K. X‐ray diffraction on single‐crystals revealed that Tl₇Bi₃I₁₆ crystallizes in the orthorhombic space group Cmcm with lattice parameters a = 2473.4(5), b = 1441.9(2), c = 3616.9(7) pm. The crystal structure can be interpreted as a layered intergrowth of fragments from the CsNiCl₃ and K₅Dy₃I₁₂ structure types with isolated [BiI₆]^3? octahedra and [Bi₂I₁₀]^4? double octahedra. Rotation and distortion of the complex anions establish coordination numbers (c.n.) between 7 and 9 for the Tl⁺ cations. Dark red crystals of trithallium(I) hexaiodo‐bismuthate(III), Tl₃BiI₆, are only accessible via hydrothermal synthesis in aqueous HI and slowly cooling from 428 to 363 K. Thermal analysis reveals a peritectoid decomposition at 540(5) K into the neighboring phases Tl₇Bi₃I₁₆ and TlI. Tl₃BiI₆ crystallizes in the monoclinic space group P2₁/c with lattice parameters a = 1352.6(3), b = 899.6(2), c = 1353.8(3) pm, and β = 104.18(3)°. In the crystal structure isolated [BiI₆]^3? octahedra are arranged according to the motif of a face‐centered pseudo‐cubic packing. Due to the tilted orientation of the [BiI₆]^3? groups the Tl⁺ cations have c.n. of 8 and 9. Although the crystal structure of Tl₃BiI₆ looks like a distorted variant of the elpasolith type, there is no symmetry relation according to a group subgroup formalism.     

Preparation of nanocrystalline BiFeO3 and kinetics of thermal process of precursor

The Bi₂Fe₂(C₂O₄)₅·5H₂O was synthesized by solid-state reaction at low heat using Bi(NO₃)₃·5H₂O, FeSO₄·7H₂O, and Na₂C₂O₄ as raw materials. The nanocrystalline BiFeO₃ was obtained by calcining Bi₂Fe₂(C₂O₄)₅·5H₂O at 600 °C in air. The precursor and its calcined products were characterized by thermogravimetry and differential scanning calorimetry, FT-IR, X-ray powder diffraction, and vibrating sample magnetometer. The data showed that highly crystallized BiFeO₃ with hexagonal structure [space group R3c(161)] was obtained when the precursor was calcined at 600 °C in air for 1.5 h. The thermal process of the precursor in air experienced five steps which involved, at first, the dehydration of an adsorption water molecule, then dehydration of four crystal water molecules, decomposition of FeC₂O₄ into Fe₂O₃, decomposition of Bi₂(C₂O₄)₃ into Bi₂O₃, and at last, reaction of Bi₂O₃ and Fe₂O₃ into hexagonal BiFeO₃. Based on Starink equation, the values of the activation energies associated with the thermal process of Bi₂Fe₂(C₂O₄)₅·5H₂O were determined. Besides, the most probable mechanism functions and thermodynamic functions (ΔS ^≠, ΔH ^≠, and ΔG ^≠) of thermal processes of Bi₂Fe₂(C₂O₄)₅·5H₂O were also determined.     

Multi-walled carbon nanotubes (MWCNTs)-bridged architecture of ternary Bi2O3/MWCNTs/Cu microstructure composite with high catalytic performance via two-step self-assembly

Binary and ternary microstructure composites based on CNTs have potential applications in many technological fields. In our works, we realized MWCNTs-bridged architecture of ternary Bi₂O₃/MWCNTs/Cu microstructure composite by two-step self-assembly. In order to verify its workability, we investigated catalytic performances of a series of additives for ammonium perchlorate (AP) thermal decomposition. The results showed that catalytic performance of Bi₂O₃/MWCNTs/Cu composite was better than those of the other additives, and the peak temperature for high-temperature AP decomposition reduced 151.6 °C; while no low-temperature AP decomposition was observed. MWCNTs have two crucial roles in catalytic enhancement on AP thermal decomposition: firstly, being to act as a supporter which can effectively disperse copper and Bi₂O₃ particles; secondly, being to act as a bridge, excited electrons from semiconductor can conduct and store on the surfaces of MWCNTs, which is beneficial for AP thermal decomposition. Therefore, MWCNTs-bridged architecture can synergistically enhance catalytic effect of copper and Bi₂O₃.     

Ag25Bi3O18, ein gemischtvalentes Bismutat

Ag₂₅Bi₃O₁₈, a Mixed Valent Bismuthate Applying oxygen pressures of 10 MPa black crystals of Ag₂₅Bi₃O₁₈ are prepared for the first time by solid state reaction of Ag₂O and ‘Bi₂O₅’. The crystal structure determination (P3 , a = 11.5887(2), c = 6,2386(1) å, Z = 1, 1369 diffractometer data, R_w = 0.034) proves the presence of trivalent (d(Bi-O) = 2.21, and 2.51 å (3×)) and pentavalent bismuth (d(Bi-O) = 2.13 å (6×)). The structure allows a change in the oxidation states (Bi³⁺ → Bi⁵⁺) by pressure induced shift of the oxygen atoms leading to a delocalisation of the 6s² valence electrons. First evidence for this phenomenon is given by the pressure dependence of the NIR reflectivity. The thermal decomposition was recorded by DTA/TG and measurements of the resistivity were performed.     

Untersuchungen zum Zustandsbarogramm und Schmelzdiagramm der Systeme BiI3?HgI2 und BiI3?I2

Investigations on the Barogram and Melting Diagram of the Systems BiI₃? HgI₂ and BiI₃? I₂ The barograms of the systems BiI₃? HgI₂ and BiI₃? I₂ are determined by total pressure measurements in a membrane manometer. The melting diagrams follow from DTA measurements and the barogram. Both systems are eutectic with eutectica at 1.5 mol% BiI₃ and 110°C for BiI₃? I₂ and 9 mol% BiI₃ and 243°C for BiI₃? HgI₂.     

Phase relations in the system Bi2O3CdO

Phase relations in the system Bi₂O₃CdO were studied in the composition range from 90-30 mole% Bi₂O₃. A new phase, Bi₂O₃ · CdO, was found to exist up to 925 K. At this temperature it decomposes to form CdO and the 5Bi₂O₃ · 3CdO phase. The 5Bi₂O₃ · 3CdO phase is stable between 925 and 963 K and melts incongruently. Below 925 K it decomposes to Bi₂O₃ · CdO and 6Bi₂O₃ · CdO. The phase 5Bi₂O₃ · 3CdO has cubic symmetry. The Sillenite-type bcc phase 6Bi₂O₃ · CdO forms above 897 K from oxide mixtures in the solid state or from fused oxide mixtures, but the compound could never be prepared as a single phase.     

A new bismuth potassium nitrate oxide, Bi1.7K0.9O2(NO3)2: Synthesis, structure, thermal behavior, and photocatalytic properties

We report here the first observation of a bismuth potassium nitrate Bi_1.7K_0.9O₂(NO₃)₂, obtained via thermal decomposition of bismuth and potassium nitrate mixtures. The new compound is orthorhombic, space group Immm (71), Z = 2, with a = 3.8698(7) Å, b = 3.8703(7) Å, and c = 24.1271(4) Å. Its crystal structure was refined from powder X-ray diffraction data by analogy with the mineral beyerite, Bi₂O₂Ca(CO₃)₂. The morphology and elemental composition of Bi_1.7K_0.9O₂(NO₃)₂ were characterized using scanning electron microscopy (SEM) with energy dispersive X-Ray spectroscopy (EDS). Its phase transformations upon heating and products of its thermal decomposition were studied using XRD, TGA and FTIR. At 440 °C, Bi_1.7K_0.9O₂(NO₃)₂ transforms to another basic bismuth potassium nitrate with demonstrates a very similar XRD pattern but slightly larger cell parameters. At 520 °C, the intermediate oxide nitrate decomposes into a mixture of crystalline α-Bi₂O₃ and KNO₃. The as prepared Bi_1.7K_0.9O₂(NO₃)₂ showed lower than TiO₂ (Degussa P25) photocatalytic activity upon decomposition of a widely used model pollutant, Rhodamine B (RhB) and photooxidation of potassium iodide under UV-vis light irradiation. Interaction with potassium iodide in alkaline media resulted in formation of Bi₅O₇I.     

Synthesis and thermal decomposition of bismuth peroxotitanate to Bi2Ti2O7

Bi-peroxotitanate was synthesized by a peroxo method and after thermal decomposition Bi₂Ti₂O₇ was obtained. DTA, TG and DSC curves of Bi₂[Ti₂(O₂)₄(OH)₆]5H₂O were recorded and used to determine isothermal conditions suitable for obtaining the intermediate samples corresponding to the phases observed during the thermal decomposition. The samples were identified by quantitative analysis, IR spectroscopy and X-ray analysis. The experimental results were used to propose a mechanism of thermal decomposition of the investigated compound to a nanosized Bi₂Ti₂O₇. The optimum conditions were also determined for obtaining Bi₂Ti₂O₇, which is applicable for piezosensors.     

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.     

浸渍-分解法制备高可见光催化活性的Bi2O3/TiO2纳米管阵列

用浸渍-分解法将Bi₂O₃纳米颗粒沉积在TiO₂纳米管壁上, 制备了Bi₂O₃/TiO₂纳米管阵列. 用电感耦合等离子体发射光谱(ICP-AES)测定了Bi₂O₃/TiO₂ 纳米管阵列的化学组分, 利用X 射线衍射(XRD)、扫描电镜(SEM)、透射电镜(TEM)和紫外-可见(UV-Vis)吸收光谱表征了所制备的样品. 通过在可见光下(λ>400 nm)降解甲基橙(MO)水溶液来评价样品的光催化活性. 结果表明, Bi₂O₃纳米颗粒均匀地沉积在TiO₂纳米管中. Bi₂O₃/TiO₂纳米管阵列具有比纯Bi₂O₃膜和N-TiO₂纳米管阵列高得多的可见光催化活性. Bi₂O₃/TiO₂纳米管阵列活性的增强是其强可见光吸收和Bi₂O₃与TiO₂之间形成的异质结的协同作用的结果.     

The compounds and the phase diagram of MoO3-Rich Bi2O3MoO3 system

The equilibrium phase diagram between 0 and slightly above 50 mole% Bi₂O₃ in the Bi₂O₃MoO₃ system has been studied by differential thermogravimetric analysis (DTA) and X-ray diffraction measurements on fused mixtures and single crystals. The results confirm the existence of the four compounds α (Bi₂O₃·3MoO₃), β (Bi₂O₃·2MoO₃), γ (Bi₂O₃·MoO)₃ and ? (～1.3Bi₂O₃·MoO₃) in the system. However, the phase diagram as well as the nature of melting of the α and γ were found disagreed with previous results. The γ compound melts incongruently at 947°C, whereas the α compound melts congruently at 662°C. The crystal class and lattice parameters of the compounds were determined based on the single crystal as well as powder pattern techniques. The results show that all four compounds have the monoclinic structure. The unit cell parameter of the β, γ, and ? compounds were found to be quite different from previously reported data. The lattice parameters obtained from X-ray analysis were also verified by density measurements of the single crystals. The polymorphism of the compounds was also investigated with single crystal samples. No polymorphic transformations for the α, β, and γ phases were detected in the work.     

Zur Kenntnis von Sr2Bi3V3O14

On Sr₂Bi₃V₃O₁₄ Single crystals of the hitherto unknown compound Sr₃Bi₃V₃O₁₄ were prepared and investigated by X-ray work. It crystallizes with triclinic symmetry, space group P1 , a = 7.0838, b = 7.1732, c = 14.1067 Å; α = 97.46, β = 98.70, γ = 110.99°, Z = 2. The crystal structure is characterized by VO₄ tetrahedra and one side open Bi³⁺ coordination inside Bi₂O₁₁ groups.     

Synthese und Kristallstrukturen von (Ph4P)4[Bi8I28], (nBu4N)[Bi2I7] und (Et3PhN)2[Bi3I11] – Iodobismutate mit isolierten bzw. polymeren Anionen

Synthesis and Crystal Structures of (Ph₄P)₄[Bi₈I₂₈], (ⁿBu₄N)[Bi₂I₇], and (Et₃PhN)₂[Bi₃I₁₁] – Bismuth Iodo Complexes with Isolated and Polymeric Anions Solutions of BiI₃ in methanol react with NaI and (ⁿBu₄N)(PF₆) or (Et₃NPh)(PF₆) to form anionic bismuth iodo complexes (ⁿBu₄N)[Bi₂I₇] 1 and (Et₃PhN)₂[Bi₃I₁₁] 2 . In 1 Bi₄I₁₆ units, and in 2 Bi₆I₂₄ units are linked by common I-atoms to onedimensional infinite chains. Reaction of BiI₃ with (Ph₄P)(PF₆) in methanol yields (Ph₄P)₄[Bi₈I₂₈] 3 . The anions of 1–3 consist of edge-sharing BiI₆ octahedra. (ⁿBu₄N)[Bi₂I₇] 1 : Space group I2/m (No. 13), a = 1 082.3(5), b = 2 597.1(13), c = 1 206.1(6) pm, β = 93.17(2)°, V = 3 385(3) · 10⁶ pm³; (Et₃PhN)₂[Bi₃I₁₁] 2 : Space group P1 (No. 2), a = 1 283.5(6), b = 1 345.9(7), c = 1 546.3(8) pm, α = 83.87(2), β = 74.24(2), γ = 68.26(2)°, V = 2 388(2) · 10⁶ pm³; (Ph₄P)₄[Bi₈I₂₈] 3 : Space group P1 (No. 2), a = 1 329.3(4), b = 1 337.0(4), c = 2 193.1(5) pm, α = 104.20(2), β = 99.73(2), γ = 100.44(2)°, V = 3 622(2) · 10⁶ pm³.     

Synthesis and properties of magnetically separable Fe3O4/TiO2/Bi2O3 photocatalysts

The Fe₃O₄/TiO₂/Bi₂O₃ composites were synthesized by a sol–gel method and used as improved photocatalysts for the degradation of methyl orange (MO) under simulated sunlight at room temperature. The as-prepared Fe₃O₄/TiO₂/Bi₂O₃ composites were characterized by X-ray diffraction, transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and diffuse reflectance spectroscopy (DRS). TEM analysis reveals that the composite has a core–shell structure and diameters of Fe₃O₄ core is about 200 nm. DRS results reveal that all composites showed red shift in optical absorption. TiO₂, Fe₃O₄, and Bi₂O₃ exist mainly as separate phases in the Fe₃O₄/TiO₂/Bi₂O₃ composites based on XPS analysis. The photocatalytic degradation of MO with the prepared photocatalysts was studied under simulated sunlight illumination. Photocatalytic reactivity test indicated that the removal efficiency of MO with the Fe₃O₄/TiO₂/Bi₂O₃ photocatalyst was higher than that of pure TiO₂ and Fe₃O₄/TiO₂. Recovery rate of Fe₃O₄/TiO₂/Bi₂O₃ photocatalysts achieved 80 % after five times reuse.