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

Reinvestigation of the V 2 O 5 –SrO system allowed final confirmation of formation of four compounds of the following stoichiometric formulas: Sr(VO 3 ) 2 , Sr 2 V 2 O 7 , Sr 3 (VO 4 ) 2 and Sr 4 V 2 O 9 . The results presented permitted solving literature controversies regarding low- and high-temperature polymorphs of strontium metavanadate(V), i.e. Sr(VO 3 ) 2 -I and Sr(VO 3 ) 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 Sr 2 V 2 O 7 . Both polymorphic forms of Sr(VO 3 ) 2 were studied by IR and SEM methods. According to the results of tests using the UV-Vis-DRS method, both polymorphs Sr(VO 3 ) 2 belong to the semiconductor class. Thermal stabilities of Sr 2 V 2 O 7 , Sr 3 (VO 4 ) 2 and Sr 4 V 2 O 9 were verified. The powder diffractogram of Sr 4 V 2 O 9 was indexed.