Thermal stability of In2(MoO4)3 and phase equilibria in the MoO3–In2O3 system

Thermal stability of a compound forming in a binary system MoO₃?CIn₂O₃ was investigated by DTA/TG, XRD and SEM methods in this study. For the first time, the diagram of phase equilibria established in the whole range of concentrations of this system's components has been constructed. The temperature and concentration ranges of the components of MoO₃?CIn₂O₃ system in which the compound In₂(MoO₄)₃ co-exists in solid state with MoO₃ or In₂O₃ or with the liquid were determined. The composition and melting point of the eutectic mixture consisting of In₂(MoO₄)₃ and MoO₃ were found.     

Synthesis and Thermal Stability of Zn4V2O9

A study of synthesis and thermal decomposition of the Zn₄V₂O₉ have been conducted by XRD method using a high-temperature X-ray attachment. A melting temperature and the way of melting that compound have been established. This revised version was published online in July 2006 with corrections to the Cover Date.     

Reaction Mechanism of Fe8W10W16O85 Synthesis

The reaction mechanism of the synthesis of Fe₈V₁₀W₁₆O₈₅ was studied by means of XRD, IR spectroscopy and DTA techniques. It was found that the intermediate in the reaction may be either FeVO₄ or FeVO₄ admixed with an unidentified phase X, depending on the reaction temperature. The IR spectrum of the phase Fe₈V₁₀W₁₆O₈₅ is reported for the first time. This revised version was published online in July 2006 with corrections to the Cover Date.     

A search for new phases in the system Fe2O3-V2O5-WO3

Studies on the three-component system Fe₂O₃-V₂O₅-WO₃ have shown the occurrence of a new, compound with molecular formula FeVW₂O₁₀. Its X-ray characteristics and its melting temperature, 865±10 °C, have been established.

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Zusammenfassung Einleitende Untersuchungen am Dreikomponentensystem Fe₂O₃-V₂ O₅-WO₃ zeigten das Auftreten einer neuen, noch nicht publizierten Verbindung der Formel FeVW₂O₁₀. Die Verbindung wurde röntgenographisch beschrieben, ihr Schmelzpunkt beträgt 865 ±10°C.

     

Phase Equilibria in the System Fe2O3–V2O5 –WO3 in the Solid State

DTA and X-ray phase diffraction methods were used to construct a solidus area projection onto the component concentration triangle plane of the system Fe₂ O₃-V₂ O₅-WO₃. This revised version was published online in August 2006 with corrections to the Cover Date.     

Reinvestigation of Phase Equilibria in the V2O5–ZnO System

A diagram of phase equilibria established in a two-component oxide system V_{2 5}–ZnO has been worked out applying differential thermal analysis and X-ray phase analysis as well as depending on investigations carried out with the aid of high-temperature X-ray attachment and scanning electron microscope linked to an X-ray microanalyser. This revised version was published online in July 2006 with corrections to the Cover Date.     

Phase Equilibria in the System V2O5–Fe8V10W16O85 and Some Properties of the Fe8V10W16O85 Phase

A phase diagram of the V₂O₅–Fe₈V₁₀W₁₆O₈₅ system were carried out using XRD and DTA methods. In addition, an indexing of Fe₈V₁₀W₁₆O₈₅ powder diffraction pattern was made and its basic crystallographic parameters were determined. Finally, the phase was studied using IR spectroscopy. This revised version was published online in July 2006 with corrections to the Cover Date.     

Phase transition study in α-Fe2WO6 compound by EPR

The temperature dependence of the EPR spectrum for the α-phase of iron tungstate has been investigated in the temperature range of 40–260 K. At temperatures betweenT ₁ ≈ 250 K andT ₂ ≈ 205 K where the antiferromagnetic phase transition occurs, a relatively narrow EPR line arising from the dominant iron(III) species has emerged, gaining intensity with the temperature increase. Its linewidth temperature evolution could be described by Huber equation, with T_N = 200 K, which is consistent with the peak seen in magnetic susceptibility measurements, while the correspondingg-factor shifts to higher fields reflecting the build-up of internal field emerging from increasing shortrange order in the spin system. At temperatures lower than T₂, a very broad and distorted EPR line with temperature dependentg-factor and linewidth has been observed reflecting the corresponding rise of the magnetic susceptibility below the antiferromagnetic phase transition, presumably arising from magnetic clusters embedded in the antiferromagnetic background.     

The homogeneity range of lyonsite-type phase existing in the CrVO4 - Co3V2O8 system

In the work presented here, the way of obtaining the phase with general formula Co_3+1.5xCr_2–x(VO₄)₄ (0 ≤ × < 0.4) is demonstrated. A new phase is detected in CrVO₄ - Co₃V₂O₈ that is formed in one of the intersection of the ternary CoO - V₂O₅ - Cr₂O₃ system. Monophasic Co₃Cr₂(VO₄)₄ (Co_3+1.5xCr_2−x(VO₄)₄, where × = 0) was obtained from both a mixture comprising CrVO₄ and Co₃V₂O₈ as well as from the mixture of CoV₂O₆ with CoCr₂O₄. The Co_3+1.5xCr_2−x(VO₄)₄ is isotypic with the those demonstrating the lyonsite-type structure. The temperature of melting for the new compound was established using the DTA methods.      

Phase equilibria in the system FeVO4-WO3 in the solid state

The DTA and X-ray powder diffraction imply the following equilibria in the system FeVO₄-WO₃ up to the solidus line: from 550 to 650–670°C, the system components remain inert towards each other in the whole concentration range; above 670°C, at up to 66.67 mol% of WO₃. FeVO₄ and FeVW₂O₁₀ are in equilibrium, whereas from 66.67 mol% of WO₃ upwards FeVW₂O₁₀ and WO₃ are in equilibrium.

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Zusammenfassung DTA Untersuchungen und Debye-Scherrer-Aufnahmen lassen darauf schließen, daß im System FeVO₄-WO₃ bis zur Soliduslinie folgende Gleichgewichte festgestellt wurden: von 550 bis 650–670°C bleiben die Systemkomponenten im ganzen Konzentrationsbereich voneinander unberührt, oberhalb 670°C sind bis zu 66.67 Molprozent WO₃ die Verbindungen FeVO₄ und FeVW₂O₁₀ im Gleichgewicht vorhanden, oberhalb 66.67 Molprozent WO₃ hingegen die Verbindungen FeVW₂O₁₀ und WO₃.