In this work it has been established which compounds finally are formed in air in the two-component CuO-V2O5 and CuO-α-Sb2O4 systems. Unknown thermal properties of CuV2O6, Cu2V2O7 and Cu11V6O26 have been established. Reactivity of the oxides and phase relations in the ternary V2O5-CuO-α-Sb2O4 system in air have been studied by using XRD and DTA methods. The results have showed the reaction of V2O5, CuO with α-Sb2O4 does not produce any compound where all the three oxides would be involved. It has been established that the α-Sb2O4 reacts and forms binary phases independently with CuO or V2O5. On the base of these results the investigated system was divided into subsidiary subsystem in which CuSb2O6 remains at equilibrium in the solid state with other phases formed in corresponding binary systems.
Phase equilibria being established in the subsolidus area of the V2O5−Cr2(MoO4)3 system at the whole component concentration range have been studied basing on DTA and X-ray phase powder diffraction. It
has been established that the system is not a real two-component system in the subsolidus area. The fact has been proved by
the presence of fields in that area, where three solid phases remain in mutual equilibrium.
The reactivity of SbVO5, a compound known since a short time, with T-Nb2O5 in solid state in air has been investigated over the whole component concentration range of a system built by these two reacting
substances. The investigation results have shown that an equimolar mixture of SbVO5 and T-Nb2O5 reacts with a subsequent formation of a hitherto unknown compound of the formula Nb2VSbO10. This compound has been characterized by the methods XRD, DTA/TG, and SEM. Its orthorhombic unit cell parameters have been
calculated, and its stability in air up to 880 ± 10 °C has been proved. At this temperature, the compound melts incongruently
with an accompanying deposition of solid Nb9VO25, i.e., of a compound that crystallizes in the binary oxide system V2O5–Nb2O5.
The investigations by XRD, DTA/TG and IR methods show that two compounds: ZnSb2O6 and Zn7Sb2O12 are formed in the ZnO-α-Sb2O4 system in air. Oxygen contained in the air participates in the synthesis of these compounds. ZnSb2O6 was observed as an intermediate phase, during the Zn7Sb2O12 synthesis. The temperature of the β→α-Zn7Sb2O12 transition was fixed at 1225±10°C. The mechanisms of the reactions of ZnSb2O6 and Zn7Sb2O12 thermal decomposition have been proposed. The IR studies of α and β-Zn7Sb2O12 have initially indicated that the structures of both polymorphous forms differ in the reciprocal connection of the SbO6 and ZnO6 octahedra and the ZnO4 tetrahedra.
Authors:Jadwiga Walczak, Elżbieta Filipek, and Monika Bosacka
The V9Mo6O40−Cr2(MoO4)3 system has been investigated using the differential thermal analysis (DTA) and X-ray phase diffraction methods. The system
has been found not to be a real two-component system over the whole component system.