Formation of Calcium Vanadates by Solid State Reactions of V2O3 with CaCO3

Abstract

The chemical reactions in mixtures of solid V₂O₃:CaCO₃ molar ratios of 1:1, 1:2 and 1:3 were investigated by XRD and TG-DSC. It was found that formation of calcium vanadates was dependent on the molar ratio of the starting materials and calcination temperature. Partial vanadium was transformed into the intermediate product Ca_0.17V₂O₅ at 400 ºC. The V₂O₅ was produced at 500 ºC. Above 600 ºC, the calcium vanadates were formed. Ca(VO₃)₂ was formed in the mixtures with V₂O₃:CaCO₃ molar ratios of 1:1 and 1:2 whereas CaV₂O₇ was formed in the mixtures with molar ratios of 1:1, 1:2 and 1:3 and Ca₃(VO₄)₂ was formed in the mixtures with molar ratios of 1:2 and 1:3. With increasing calcination temperature, Ca(VO₃)₂ was transformed into Ca₂V₂O₇ or even Ca₃(VO₄)₂.