Reinvestigation of thermal and other properties of compounds from the V2O5–SrO system.

Reinvestigation of the V₂O₅–SrO system allowed final confirmation of formation of four compounds of the following stoichiometric formulas: Sr(VO₃)₂, Sr₂V₂O₇, Sr₃(VO₄)₂ and Sr₄V₂O₉. The results presented permitted solving literature controversies regarding low- and high-temperature polymorphs of strontium metavanadate(V), i.e. Sr(VO₃)₂-I and Sr(VO₃)₂-II. The polymorphic transformation of both varieties that crystallize in the orthorhombic system was proved to be reversible and take place at 530 °C. Strontium metavanadate(V) was found to melt incongruently at 670 °C with deposition of solid Sr₂V₂O₇. Both polymorphic forms of Sr(VO₃)₂ were studied by IR and SEM methods. According to the results of tests using the UV-Vis-DRS method, both polymorphs Sr(VO₃)₂ belong to the semiconductor class. Thermal stabilities of Sr₂V₂O₇, Sr₃(VO₄)₂ and Sr₄V₂O₉ were verified. The powder diffractogram of Sr₄V₂O₉ was indexed. [ABSTRACT FROM AUTHOR]