The vibrational spectra of the intermediate compounds in the system Y2O3P2O5 and Gd2O3P2O5

The Infrared- and Raman-spectra of the intermediate compounds were studied for clues to their structural behavior as related to luminescence response. It was found that the degree of polymerization of PO₄ polyhedra increases in the phosphate-rich region and perhaps in the RE-oxide-rich region as well which was evident from the shift of stretching bands towards the higher energy side. Except in orthophosphates, the PO₄ polyhedra occupy more than one non-equivalent lattice site in all the phosphates.     

Hydrogen insertion compounds of V6O13 and V2O5

Hydrogen insertion compounds H_xV₆O₁₃ (0<x?7.3) have been synthesised and characterised. Unit-cell dimensions, determined from powder X-ray analysis, indicate that the hydrogen-insertion reaction proceeds topotactically. In addition, a low-hydrogen-content phase of H_xV₂O₅ of similar structure to V₂O₅ has been prepared.     

An ESR study of the heterogeneous system Cr2O3V2O5

An ESR study of the ‘products’ of the high temperature solid state reaction xCr₂O₃+yV₂O₅ ($\text{0.05≦(}\text{x}\text{y}\text{)≦2.0}$), aided by powder X-ray diffraction and IR spectra, has revealed (i) ‘unfamiliar’ paramagnetic intermediates Cr⁴⁺ and Cr⁵⁺, (ii) provided some clues to the oxidation of Cr³⁺ to Cr⁶⁺, and (iii) demonstrated a variety of exchange interactions involving V⁴⁺ and Cr³⁺.     

Observation of broadband infrared luminescence in a novel Bi-doped P2O5-B2O3-Al2O3 glass

A novel Bi-doped P₂O₅-B₂O₃-Al₂O₃ glass was investigated, and strong broadband NIR (near infrared) luminescence was observed when the sample was excited by 445 nm, 532 nm, 808 nm and 980 nm lasers, respectively. The max FWHM with 312 nm, the lifetime with 580 μs and the σ_emτ product with 5.3 × 10^− 24 cm² s were obtained which indicates that this glass is a promising material for broadband optical amplifier and tunable laser. The effect of the introduction of B₂O₃ on the glass structure and Bi-ions illuminant mechanism were discussed and analyzed. It is suggested that the introduction of B₂O₃ makes the glass structure closer, and the broadband NIR emission derives from Bi⁰:²D_3/2 → ⁴S_3/2 and Bi⁺:³P₁ → ³P₀ transitions.     

V3.2W1.8O13 and studies of the V2O5WO3VO2 ternary system

The tungsten/vanadium ratios for the known ternary compounds in the V₂O₅WO₃VO₂ chemical system are characterized. The compounds V_2.5W_.5O₇ and V₂WO_7.5 are the n = m = 3 and n = m = 4 members of a sreies of M-niobia like crystallographic shear structures. We have found the n = m = 5 member of the series at the composition V_3.2W_1.8O₁₃, and report its crystallographic unit cell, powder x-ray diffraction pattern and range of temperature stability.     

X-ray diffraction studies of glasses in the TeO2V2O5 system

The short-range order in glasses of the TeO₂V₂O₅ system is studied with the aid of X-ray diffraction. It is found that the main structural units in most of the glasses are VO₅- and TeO₃-groups. The assumption is made that their structures gradually change; sheet complexes are formed close to V₂O₅; chains - around 2TeO₂V₂O₅, and a tridimensional aperiodic network in glasses from TeO₂.     

Studies on the system V3O5 /1b Ti3O5

The system (V_1?xTi_x)₃O₅ has been studied by means of X-ray powder photography, DTA and magnetic susceptibility measurements. A continuous series of solid solutions has been found for samples prepared at 1175 K, while samples prepared at 1275 K showed the solid solubility in the V₃O₅ end phase to be limited by $\text{x}\text{< 0.7}$ DTA studies have shown that the peak associated with the V₃O₅(low) /1b V₃O₅(high) transition disappears at $\text{x}\text{= 0.024}$. The DTA studies have also confirmed the existence of a phase transition in γ-Ti₃O₅ ($\text{x}\text{= 1}$) at 227 K.     

Microdurete de monocristaux de V2O5

Microhardness measurements of V₂O₅ single crystals were undertaken in order to study the anisotropy of their mechanical properties. Results are presented for both Vickers and Knoop hardness values on (100), (010) and (001) planes of orthorhombic V₂O₅ single crystals.A strong anisotropy is observed in each plane. As expected, hardness appears to be particularly small when the diamond indenter is parallel to the clivage directions in the (100) and (001) planes. A remarkably small value is observed along the [100] direction in the (001) plane, which could be related to the model proposed by Gillis in order to explain the structural charge into V₆O₁₃ occuring in non-stoichiometric V₂O₅.     

Conversion of V2O5·xH2O into orthorhombic V2O5 single-crystalline nanobelts

Orthorhombic V₂O₅ single-crystalline nanobelts have been synthesized by hydrothermal treating V₂O₅·xH₂O precipitate derived from aqueous solution of V₂O₅ and H₂O₂. The synthetic method is facile, fast, environmental friendly, and easy to scale up. The V₂O₅ single-crystalline nanobelts are 30-80 nm in width, 30-40 nm in thickness, and lengths up to several tens of micrometers. The V₂O₅·xH₂O precursor is crucial for the formation of orthorhombic V₂O₅ single-crystalline nanobelts. The influences of synthetic parameters, such as reaction time and reaction temperature, on the crystal structures and morphologies of the resulting products have been investigated. Time-dependent experiments show that V₂O₅·xH₂O are dehydrated gradually and converted into orthorhombic V₂O₅ single-crystalline nanobelts. High reaction temperature also favors the formation of orthorhombic V₂O₅ nanobelts.     

Phase transition in V3O5

A phase transition at 420°K previously unreported, has been discovered in V₃O₅. The transition is characterized by an endothermic DTA peak on heating and an abrupt change in the electrical resistivity at the same temperature. Results from X-ray analysis of the V₃O₅ samples exhibiting the transition agree very well with the values reported by Andersson (1). Powder diffraction analysis of the high temperature phase indicates that there is a small change in the cell volume but the crystal apparently conserves its symmetry through the transition.     

Formation and properties of glasses in the CaF2AlF3P2O5 system

Glasses from the system CaF₂AlF₃P₂O₅ have been synthesized. Glass formation characteristics, thermal expansion, and optical transmission of these glasses in the visible and infrared regions are described. Incorporation of P₂O₅ in the system greatly suppressed the spontaneous crystallization tendencies of the CaF₂AlF₃ binary system. The glasses obtained from the system transmit in the mid-infrared range. A strong absorption band centerd at 4.8 microns is a characteristic of these glasses. The absorption band is related to the presence of P₂O₅ in the glass.     

Magnetic anisotropy of V3O5

The magnetic anisotropy of V₃O₅ was investigated by magneto-torque measurements in the temperature range from 4.2 to 300 K. It has been confirmed that the Néel temperature is about 75 K and that two of the three principal axes vary with temperature in both the paramagnetic and antiferromagnetic states. The results are explained on a simplified four-sublattice model.     

Carrier transport mechanisms in the V2O5-n-Si system

The mechanisms of carrier transport were investigated by measuring the I-V characteristics and the capacitance in a V₂O₅-n-Si system which was produced by evaporation and oxidation of vanadium onto silicon single-crystal plates. Potential barriers of 0.52 and 0.37 eV were found at the V₂O₅-n-Si interface as well as barriers of 0.1 eV at the V₂O₅ pre-interface regions for both n-Si and the gold electrode. The dependence on voltage of the height of the barriers leads to different carrier transport processes depending upon the magnitude and the polarity of the applied voltage. The conduction mechanisms occurring in this system include high field effects such as Poole-Frenkel, Schottky and Fowler-Nordheim emission as well as space charge injection. A thin SiO₂ layer about 8 Å thick was detected between the n-Si and the V₂O₅ layer. The structure of the V₂O₅ film was found to be amorphous rather than crystalline. The parameters of this V₂O₅ layer were evaluated.     

Influence of modifier oxides on some physical properties of antimony borate glass system doped with V2O5

Three series of glasses, of the composition 20 MO (M = Ca, Pb, Zn)–40 Sb₂O₃–(40 − x) B₂O₃:xV₂O₅, with six values of x ranging from 0 to 1 mol% were prepared. The samples were characterized by X-ray diffraction, scanning electron microscopy, EDS and differential scanning calorimetric techniques. The comparison of DSC data among the three series has indicated high glass forming ability for ZnO mixed glasses. Dielectric properties over a range of frequency and temperature, optical absorption, ESR spectra at room temperature and IR spectra have been investigated. The variations observed in all these properties due to different modifiers as a function of the concentration of V₂O₅ have been analyzed in the light of different oxidation states and environment of vanadyl ions in these glasses. The analysis of these results indicated that the ZnO mixed glasses are more stable against devetrification and possess high insulating strength when compared with PbO and CaO mixed glasses.     

Sintering, crystallization, and properties of a low-viscosity SnO–MgO–P2O5 glass

A lead-free, low-viscosity SnO–MgO–P₂O₅ glass powder was fabricated. Sinterability, wetting, flowability, crystallization, and the resulting properties of the glass powder were investigated. It is shown that the powder compact can be fully densified above 362 °C and show good wet to the substrate above 417 °C. The properties (coefficient of thermal expansion and chemical durability) of the sintered glass depend on the sintering temperature and are discussed in terms of the development of crystalline phases during sintering.     

Glasses and glass-ceramics in the SrO–TiO2–Al2O3–SiO2–B2O3 system and the effect of P2O5 additions

The glass formation abilities of various compositions in SrO–TiO₂–Al₂O₃–SiO₂, SrO–TiO₂–B₂O₃–SiO₂, SrO–TiO₂–Al₂O₃–B₂O₃, and SrO–TiO₂–Al₂O₃–SiO₂–B₂O₃ systems were studied. Many new compositions were found to be suitable for the casting of crack-free, optically clear glasses of different color and with glass transition temperatures ranging from 595 to 775 °C. The crystallization behavior, structure, and thermal expansion behavior of selected glasses were analyzed by DTA, XRD, dilatometry, and heat treatment. The effect of P₂O₅ on the glass structure and crystallization behavior was also studied. P₂O₅ played a dual role depending on composition. In some glasses it acted as a nucleating agent while in others it suppressed crystallization. Heat treatment of borate and borosilicate glasses transformed them into glass-ceramics while comparable SrO–TiO₂–Al₂O₃–SiO₂ glasses showed a lower tendency to crystallize and form glass-ceramics under the same conditions.     

The system Eu2O3SrOV2O3 at 1400°C

Phase relations in a portion of the system Eu₂O₃SrOV₂O₃ have been investigated at 1400°C and a reduced pressure (10^?4mmHg). On heating, part of the trivalent vanadium was oxidized to the tetravalent state by atomospheric oxygen. The following ternary-phase solid solutions were identified: Eu_1?xSr_xVO_3?0.1x, SrO·2Eu_1?x?Sr_xVO_3?0.1x and SrO·Eu_1?xSr_xVO_3?0.1x.     

Enhancement of Sinter Densification of SrO-BaO-Nb2O5-SiO2 Tungsten-Bronze Glass-Ceramics by Doping with P2O5

Densification behaviors of SrO—BaO—Nb₂0₅—SiO₂ based glass—ceramics prepared by conventional sintering were investigated with an emphasis on the influence of P₂O₅ content.Although P₂0₅ dopant did not modify the surface crystallization mechanism,it resulted in a decrease of the glass transition temperature,which facilitates the viscous glass flow necessary for sintering.However,premature crystallization of（Sr,Ba）Nb₂O₆ induced by addition of excess amount of P₂0₅ essentially retarded sintering due to the formation of closed pores in the matrix.The SrO-BaO-Nb₂0₅-Si0₂ glass with 1.0 mol%P₂0₅（SBN-1P） showed the best sinter densification,which was accomplished at about 850℃.     

Hydratation et texture fibreuse de V2O5 amorphe

Reversible hydration of amorphous V₂O₅ has been performed in order to study the effect of water upon the properties of the oxide. A drastic change of the ESR spectrum is observed, which turns from anisotropic to isotropic upon hydration. This has been interpreted in terms of a brownian motion which, by analogy with the V₂O₅ gels, is supposed to be due to the fibrous texture of the amorphous oxide.     

Cluster formation in Ag2O-P2O5-CdCl2 glass system

Ag₂O-P₂O₅ and Ag₂O-P₂O₅-20 wt% CdCl₂ glasses were prepared by melt quenching method and characterized with the help of several experimental techniques. Powder X-ray diffraction study indicated that the glasses are amorphous in nature. DSC studies showed that CdCl₂ doped glass is chemically more durable. Electrical conductivity and ionic transference number measurements have shown that both the glasses are ionic conductors with Ag⁺ ions as the charge carriers. The electrical conductivity of the doped glass is found to be higher than the undoped one. Structures of the glasses have been proposed on the basis of IR spectral analysis. From SEM studies it has been inferred that addition of 20 wt% CdCl₂ modifies the morphology of Ag₂O-P₂O₅ glass and in its presence formation of clusters composed of nanofibers occur.