Facile fabrication of VO2(M) by thermolysis of ammonium metavanadate (NH4VO3) under sealed condition

Abstract

NH4VO3 is an important vanadium source for the preparation of VO2. In the previous studies, the extra gas or solid reagents consumption is necessary for the preparation of VO2 by using NH4VO3 as vanadium source. The current work proposed a facile way for the fabrication of VO2 (M) by the thermolysis of NH4VO3 under the sealed atmosphere without extra gas or solid reagents consumption. The VO2(M) could be successfully synthesized by two step—thermolysis of NH4VO3 at 400 ​°C under the sealed condition and heat treatment of VO2(B) at 500 ​°C under the N2 condition. The dosage of NH4VO3 and decomposition temperature had significant influences on the thermolysis process under the sealed condition. The NH3 produced by the thermolysis provided a protective atmosphere that prevented the oxidization of VO2(B) by residual O2 in the sealed reactor. Furthermore, the VO2 (M) could be prepared directly under the sealed atmosphere by increasing reaction temperature to 700 ​°C. In this process, NH4VO3 underwent a phase transition as the follows: NH4VO3→ammonium vanadium bronze→VO2(B)→VO2(M). The directly synthesized VO2(M) at 700 ​°C by the thermolysis of NH4VO3 under the sealed condition showed great environmental stability and phase transition performance.