Synthesis, characterization and formation mechanism of metastable phase VO_2(A) nanorods

摘要

Pure phase VO_2(A) nanorods were synthesized via the reduction of V_2O_5 by oxalic acid during the hydrothermal treatment. Two sets of samples were prepared by varying both system temperature and reaction time under a filling ratio of 0.40 for observing the formation and evolution of VO_2(A) nanorods. Structures were characterized by X-ray diffraction, scanning and transmission electron microscopies, respectively. It was found that VO_2(B) was firstly formed and then transformed into VO_2(A) as the increasing system temperature or extending reaction time. An assembling and following crystal adjustment was proposed for explanation the formation process of VO_2(A) from VO_2(B). For VO_2(A) nanorods, the phase transition temperature of 169.7℃ was higher than that of the VO_2(A) bulk, it might be ascribed to the lower crystallinity or nonstoichiometry in VO_2(A) nanorods. VO_2 nanostructures with controllable phases and properties should find their promising applications in a single VO_2 nanodevice.