Ein neues Oxochromat: SrNi2Cr8O15 vom Strukturtyp BaV10O15

Summary A new quaternary oxochromate(III) was prepared by solid state reaction. Single crystal X-ray investigations of SrNi₂Cr₈O₁₅ show that this compound belongs to the BaV₁₀O₁₅ type. [Space group D _2h ¹⁸ - Ccmb,a=10.042;b=11.413;c=9.260 Å;Z=4.] Ni²⁺ and Cr³⁺ occupy the octahedrally coordinated point positions statistically. The surrounding of Sr²⁺ is similar to the iso- and heteropolyacids.

     

Optical transitions of Er3+/Yb3+ codoped TeO2-WO3-Bi2O3 glass

Optical absorption and emission properties of the Er3+/Yb3+ codoped TeO2-WO3-Bi2O3 (TWB) glass has been investigated. The transition probabilities, excited state lifetimes, and the branching ratios have been predicted for Er3+ based on the Judd-Ofelt theory. The broad 1.5 microm fluorescence was observed under 970 nm excitation, and its full width at half maximum (FWHM) is 77 nm. The emission cross-section is calculated using the McCumber theory, and the peak emission cross-section is 1.03 x 10(-21) cm2 at 1.531 microm. This value is much larger than those of the silicate and phosphate glasses. Efficient green and weak red upconversion luminescence from Er3+ centers in the glass sample was observed at room temperature, and the upconversion excitation processes have been analyzed.     

Phase equilibria in the V2O5-Cr2O3 system

The phase equilibria in the total range of component concentrations in the V₂O₅-Cr₂O₃ system up to 1000 °C were studied by means of phase powder diffraction and DTA. Two compounds exist in the system: CrVO₄, melting incongruently at 860±5 °C, and Cr₂V₄O₁₃, which decomposes in the solid state at 640±5 °C to CrVO_4(s) and V₂O_5(s). At 645±5 °C, CrVO₄ and V₂O₅ form a eutectic mixture with the CrVO₄ content not exceeding 2% mol.

---

Zusammenfassung Mittels DTA und Pulverdiffraktionsaufnahmen wurde das Phasengleichgewicht des Systems V₂O₅-Cr₂O₃ bis 1000 °C im gesamten Konzentrationsbereich untersucht. Innerhalb des Systemes existieren zwei Verbindungen: CrVO₄ mit einem inkongruentem Schmelzpunkt bei 860±5 °C und Cr₂V₄O₁₃, das sich in festem Zustand bei 640±5 °C in CrVO_4(s) und V₂O_5(s) zersetzt. Bei 645±5 °C bilden CrVO₄ und V₂O₅ ein eutektisches Gemisch mit einem maximalen CrVO₄-Gehalt von 2 mol%.

---

DTA V₂₅-Cr₂₃ 1000° . : CrVO₄, 860±5° Cr₂V₄O₁₃, 640±5° CrVO₄ V₂O₅, 645±5° CrVO₄, 2 %.

     

Phase Equilibria in the Fe8V10W16O85-Fe2O3 and Fe8V10W16O85-Fe2WO6 Systems

Using DTA and X-ray phase diffraction methods, a diagram of phase equilibria established in two sections of a tricomponent oxide triangle Fe₂O₃-V₂O₅-WO₃was constructed, that is, in the sections: Fe₈V₁₀W₁₆O₈₅-Fe₂O₃and Fe₈V₁₀W₁₆O₈₅-Fe₂WO₆. This revised version was published online in July 2006 with corrections to the Cover Date.     

Synergistic Catalysis of SnO2/Reduced Graphene Oxide for VO2+/VO2+ and V2+/V3+ Redox Reactions

In spite of their low cost, high activity, and diversity, metal oxide catalysts have not been widely applied in vanadium redox reactions due to their poor conductivity and low surface area. Herein, SnO₂/reduced graphene oxide (SnO₂/rGO) composite was prepared by a sol–gel method followed by high-temperature carbonization. SnO₂/rGO shows better electrochemical catalysis for both redox reactions of VO²⁺/VO₂⁺ and V²⁺/V³⁺ couples as compared to SnO₂ and graphene oxide. This is attributed to the fact that reduced graphene oxide is employed as carbon support featuring excellent conductivity and a large surface area, which offers fast electron transfer and a large reaction place towards vanadium redox reaction. Moreover, SnO₂ has excellent electrochemical activity and wettability, which also boost the electrochemical kinetics of redox reaction. In brief, the electrochemical properties for vanadium redox reactions are boosted in terms of diffusion, charge transfer, and electron transport processes systematically. Next, SnO₂/rGO can increase the energy storage performance of cells, including higher discharge electrolyte utilization and lower electrochemical polarization. At 150 mA cm⁻², the energy efficiency of a modified cell is 69.8%, which is increased by 5.7% compared with a pristine one. This work provides a promising method to develop composite catalysts of carbon materials and metal oxide for vanadium redox reactions.     

Synthesis and electrical transport of single-crystal NH4V3O8 nanobelts

Monoclinic NH(4)V(3)O(8) single-crystalline nanobelts with widths of 80-180 nm, thicknesses of 50-100 nm, and lengths up to tens of micrometers have been synthesized at large scale in an ammonium metavanadate solution by a templates/catalysts-free route. Such nanobelts grow along the direction of [010]. The individual NH(4)V(3)O(8) nanobelt exhibits nonlinear, symmetric current/voltage (I/V) characteristics, with a conductivity of 0.1-1 S/cm at room temperature and a dielectric constant of approximately 130. The dominant conduction mechanism is based on small polaron hopping due to ohmic mechanism at low electric field below 249 V/cm due to Schottky emission at medium electric field between 249 and 600 V/cm and due to the Poole-Frenkel emission mechanism at high field above 600 V/cm.     

Phase diagram of V2O5-MoO3-Ag2O

Phase equilibria in the V₂O₅-Ag₂O system were investigated at a constant pressure of oxygen (0.2 atm) and the phase diagram found under these conditions was compared with the results of the authors who investigated the same system in vacuum and at an oxygen pressure of 1 atm. On the basis of all these results, an attempt was made to construct the hypothetical diagram of V₂O₅-Ag₂O-O₂.     

Phase diagram of the V2O5-MoO3-Ag2O system

The phase diagram of the MoO₃-Ag₂O system was constructed. A comparison of the phase diagram presented here with the phase diagram of MoO₃-Ag₂MoO₄ system presented in [2] revealed some discrepancies.It was found that phase equilibrium in MoO₃-Ag₂O system could be reached only after cooling the previously melted mixtures of silver and molybdenum oxides.

---

Zusammenfassung Es wurde das Phasendiagramm des Systemes MoO₃-Ag₂O erstellt. Der Vergleich dieses Phasendiagrammes mit dem des in (2) beschriebenen Systemes MoO₃-Ag₂MoO₄, ergeben sich einige Unterschiede.Man fand, da\ ein Phasengleichgewicht im System MoO₃-Ag₂O nur nach Abkühlen des zuvor geschmolzenen Gemisches aus Silber- und MolybdÄnoxides erreicht werden kann.

---

---

The author wishes to thank Professor M. Figlarz from Université de Picardie, Amiens for giving the possibility of carrying out in his laboratory a part of the experiments described.     

Deuterium exchange in the systems of H2O+/H2O and H3O+/H2O

The reactions of H₂O⁺, H₃O⁺, D₂O⁺, and D₃O⁺ with neutral H₂O and D₂O were studied by tandem mass spectrometry. The H₂O⁺ and D₂O⁺ ion reactions exhibited multiple channels, including charge transfer, proton transfer (or hydrogen atom abstraction), and isotopic exchange. The H₃O⁺ and D₃O⁺ ion reactions exhibited only isotope exchange. The variation in the abundances of all ions involved in the reactions was measured over a neutral pressure range from 0 to 2 × 10⁻⁵ Torr. A reaction scheme was chosen, which consisted of a sequence of charge transfer, proton transfer, and isotopic exchange reactions. Exact solutions to two groups of simultaneous differential equations were determined; one group started with the reaction of ionized water, and the other group started with the reactions of protonated water. A nonlinear least-squares regression technique was used to determine the rate coefficients of the individual reactions in the schemes from the ion abundance data. Branching ratios and relative rate coefficients were also determined in this manner.A delta chi-squared analysis of the results of the model fitted to the experimental data indicated that the kinetic information about the primary isotopic exchange processes is statistically the most significant. The errors in the derived values of the kinetic information of subsequent channels increased rapidly. Data from previously published selected ion flow tube (SIFT) study were analyzed in the same manner. Rigorous statistical analysis showed that the statistical isotope scrambling model was unable to explain either the SIFT or the tandem mass spectrometry data. This study shows that statistical analysis can be utilized to assess the validity of possible models in explaining experimentally observed kinetic behaviors.     

Photoluminescent Property Effect of Sc3+ on Er3+/y3+/yb3+ Doped Al2O3 Powders

The photoluminescence (PL) property effect of Sc3+ on the Er3+/Y3+/Yb3+ doped Al2O3 powders prepared by sol-gel method has been investigated. The X-ray diffraction (XRD) and transmission electron microscopy (TEM) implied that the distribution of dopants (Er3+ , Y3+ , Yb3+ , Sc3+) was improved effectively with the rise of Sc3+ concentration. The Fourier transform infrared spectra (FTIR) results demonstrated that the ligand around the quenching center -OH and the population of -OH were altered by introducing different amounts of Sc3+ . The PL intensity centered at 1530 nm was increasingly improved with the rise of Sc3+ concentration, as well as the corresponding full widths at the half maximum (FWHM) and lifetime. The optimized PL intensity was 4.7 times higher than that non-Sc3+ doped sample for the Al2O3 powders codoped with 10mol% Sc3+ . This material can be promising candidates for optical fiber amplifier.     

Mg2Na2V10O28·20H2O and Mg3V10O28·28H2O

The crystal structures of dimagnesium disodium decavanadate icosahydrate, Mg₂Na₂V₁₀O₂₈·20H₂O, (I), and trimagnesium decavanadate octacosahydrate, Mg₃V₁₀O₂₈·28H₂O, (II), have been determined by single‐crystal X‐ray diffraction. They crystallize with monoclinic (C2/c) and triclinic () symmetry, respectively. All the Mg²⁺ cations in (I) and (II) are octahedrally coordinated by six water mol­ecules. The Na⁺ cations in (I) are coordinated by three water mol­ecules and three O atoms of the decavanadate anions, and link the latter into a three‐dimensional network. The decavanadate anions in (II) are not linked to one another.     

Phase equilibria up to the solidus line in the system Fe2O3−Fe8V10W16O85

Phase equilibria up to the solidus line in the system Fe₂O₃?Fe₈V₁₀W₁₆O₈₅ were determined by means of X-ray phase powder diffraction and differential thermal analysis. This system is one of the intersections of the three-component system Fe₂O₃?V₂O₅?WO₃. The studies revealed that this is not a real binary system, even in the solid state.     

Upconversion luminescence and ratiometric temperature sensing behavior of Er3+/Yb3+-codoped CaY2Ge3O10 germanate

1. Download : Download high-res image (173KB)
2. Download : Download full-size image

     

Carrier-mediated selective transport of Ga3+ from Ga3+/Al3+ binary solutions and Cu2+ from Cu2+/Zn2+ binary solutions through alkylated cupferron-impregnated membrane

Selective transport of Ga³⁺ and Cu²⁺ was performed with a polytetrafluoroethylene membrane impregnated with long-chain alkylated cupferron (ammonium salt of N-(alkylphenyl)-N-nitrosohydroxylamine). Ga³⁺ is selectively concentrated from Ga³⁺/Al³⁺ binary solutions and Cu²⁺ from Cu²⁺/Zn²⁺ binary solutions with counter flow of H⁺ in both cases.     

Optical transitions of Sm3+ in oxide glasses

Eigenvectors of the 4f⁵ electronic configuration of Sm³⁺ were calculated in intermediate coupling, and used to obtain the reduced matrix elements U^(λ). Absorption spectra of Sm³⁺ were recorded in phosphate, borate, germanate and tellurite glasses. The Judd-Ofelt $\text{Ω}{}_{\mathrm{\lambda }}\text{'}\text{s}$ intensity parameters were then deduced from the measured oscillator strengths by least-squares fitting. Radiative transition probabilities and integrated cross-sections of stimulated emissions are obtained. Calculated branching ratios and decay lifetimes are compared with the experimental values.     

Cu3V10O28·24H2O and CuNa4V10O28·23H2O

The crystal structures of tricopper decavanadate tetracosa­hydrate, (I), and copper tetra­sodium decavanadate tricosa­hydrate, (II), have been determined by single‐crystal X‐ray diffraction. Both compounds exhibit a catenary structure consisting of [V₁₀O₂₈]⁶⁻ anions linked by Cu²⁺ cations in (I) or by Na⁺ cations in (II). Compound (II) also contains a polymeric linear array of edge‐sharing [Na(OH₂)₆]⁺ and [Cu(OH₂)₆]²⁺ octahedra. In both compounds, the [V₁₀O₂₈]⁶⁻ ions lie about inversion centres and the Cu²⁺ ions in (I) also lie about inversion centers.     

The electrical conductivity of Dy3+/Sc3+ co-doped CeO2 solid electrolytes

Journal of Solid State Electrochemistry - The Dy3+ single doped and Dy3+/Sc3+ co-doped CeO2 electrolyte powders were successfully synthesized by a sol–gel method followed by calcination at...     

Phase Equilibria in the V2O5-Sb2O4 System

Differential thermal analysis (DTA) and X-ray powder diffraction (XRD) were used to study phase equilibria, established in air in the V₂O₅-Sb₂O₄ system up to 1000°C. It has been found that there is a new phase =SbVO₅. The =SbVO₅ has been prepared by two methods: by heating equimolar mixtures of V₂O₅ and α-Sb₂O₄ in air and by oxidation of the known phase of rutile type obtained in pure argon at temperatures between 550 and 650°C. Thermal decomposition of =SbVO₅ in the solid state starts at 710°C giving off oxygen. The results provide a basis for constructing only a part of the phase diagram of the investigated system (up to 50.00 mol% Sb₂O₄). This revised version was published online in July 2006 with corrections to the Cover Date.