The fabrication of V2O3 by using NH4VO3 as vanadium source without extra reductant under sealed condition

Abstract

NH3 produced by the thermolysis of NH4VO3 is a good reductant for the fabrication of low valence vanadium oxides. In this study, the thermodynamics of V–O and V–O–NH3 was analyzed to provide a theoretical basis for the preparation of V2O3 using NH4VO3. Based on this analysis, the thermolysis processes of NH4VO3 under different conditions (air, nitrogen and sealed atmosphere) were investigated. Compared with the air and nitrogen conditions, the sealed condition fully utilises NH3 escaping from NH4VO3 and is more suitable for the low-cost fabrication of V2O3. First, the only product of thermolysis under the dynamic air condition was V2O5 due to the high oxygen partial pressure. Second, the fabrication of VO2 under the static air and nitrogen conditions was feasible with a high temperature (＞625 ​°C). The formation of VO2 in these conditions is explained by the instability of V2O5, which decomposed into VO2 at a temperature higher than 625 ​°C. Finally, under the sealed condition at 700 ​°C, pure V2O3 was obtained and NH4VO3 underwent the following phase transition: NH4VO3→ (NH4)4(V6O16) → V4O7→ V3O5→V2O3.