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Synteza i właściwości fizykochemiczne nowych faz w układach tlenków V2O5, MoO3, alfa-Sb2O4

100%

Filipek E.

Prace Naukowe Politechniki Szczecińskiej. Katedra Chemii Nieorganicznej i Analitycznej

2007

tom Nr 602 (1)

5-137

Przedstawione badania trójskładnikowego układu tlenków V2O5-MoO3-alfa-Sb2O4 poprzedzono pracami weryfikującymi dane na temat dwóch układów dwuskładnikowych, badanych w atmosferze powietrza, a mianowicie V2O5-alfa-Sb2O4 oraz MoO3-alfa-Sb2O4.

The presented work comprises a literature review, describing the current state of knowledge about both the ternary system V2O5-MoO3-alpha-Sb2O4 and its lateral binary systems V2O5-alpha-Sb2O4. MoO3-alpha-Sb2O4 and V2O5-MoO3, as well as results of investigations conducted in order to get a comprehensive cognizance of physicochemical properties of new phases formed in these systems in air. The main research was performed by applying several investigation techniques, i.e. XRD, DTA/TG, IR, SEM/EDX/WDX and XPS. The research on the ternary oxide system was preceded by investigations verifying and supplementing the data about two of its lateral systems, V2O5-alpha-Sb2O4 and MoO3-alpha-Sb2O4. It has been proven that in the binary system V2O5-alpha-Sb2O4 in the atmosphere of air beside Sb0.92V0.92O4 a new compound of the formula SbVO5 is formed. The optimal temperature of its synthesis, its thermal properties. XRD characteristics and density have been determined. As a result of indexing the powder diffraction pattern of SbVO5 the basic parameters of its monoclinic unit cell and its density have been calculated. On the base of investigations of phase equilibria being established in the systems V2O5-alpha-Sb2O4 and MoO3-alpha-Sb2O4 in air, phase diagrams of these systems over the whole components concentration range up to 1000°C have been constructed. As a result of the research on the ternary oxide system V2O5-MoO3-alpha-Sb2O4 it has been found that its components enter into reactions forming two new phases, i.e. the compound Sb3V2Mo3O21 and a solid solution of MoO3 in SbVO5. Their synthesis conditions, basic thermal properties, densities and XRD characteristics have been determined. On the base of indexing the powder diffraction pattern of the compound Sb3V2Mo3O21 the basic parameters of its orthorhombic unit cell have been calculated. The oxidation states of the elements in Sb3V2Mo3O21 have been determined by using the methods of EPR, NMR and XPS. The formation mechanism and the homogeneity area of the solid solution of MoO3 in SbVO5 as well as the way of compensating the excessive positive charge - that resulted from an incorporation of Mo6+ into the crystal lattice of SbVO5 instead of V5+ or/and Sb5+ - have been established. The phase equilibria being settled in two intersections of the title ternary system, i.e. SbVO5-MoO3 and SbVO5-Sb3V2Mo3O21, as well as in the ternary system under consideration have been investigated, which enabled the system V2O5-MoO3-alpha-Sb2O4 to be divided into eight subsidiary subsystems.

Magnetic resonance study of SbVO5 thermal decomposition products

51%

Typek J. , Filipek E. , Maryniak M. , Guskos N.

Materials Science Poland

2005

tom Vol. 23, No. 4

1047--1054

A new SbVO5 compound, which can be synthesized from an equimolar mixture of Sb2O3/V2O5 or ?-Sb2O4/V2O5 oxides by heating in air to temperatures below 650 °C, is stable in air up to 710 °C and in argon atmosphere up to ~645 °C. At higher temperatures it decomposes into a phase with a rutile-type structure. Using electron spin resonance (ESR) we have studied the magnetic properties of the thermal decomposition products of SbVO5 in air (sample 1D) and in argon atmosphere (sample 2D), as well as two phases of the of the rutile-type structure (samples 3S and 4S) synthesized at conditions similar to the previous two samples. The ESR spectra of all four samples consisted mostly of two types of lines: a narrow line (designated as the N component) and a very broad line (designated as the VB component). Close inspection of the ESR parameters for these components allowed the samples to be grouped according to the environment they were annealed in (air or oxygen-free argon). The origin of these lines and the implications concerning the phase composition of the decomposition products are discussed. ESR results confirm that the solid decomposition product of SbVO5 in air is a nonstoichiometric compound with a rutile structure and formula Sb0.95+V0.13+V0.84+ 0.2O4 and in argon a near-stoichiometric V4+Sb5+O4.5.