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

Filipek E.

Prace Naukowe Politechniki Szczecińskiej. Katedra Chemii Nieorganicznej i Analitycznej

2007

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.