Influence of different additives on the synthesis of VO2 polymorphs

Abstract Monoclinic vanadium dioxide VO 2 (M) shows a fully reversible first-order metal-to-insulator transition (MIT) with the phase transition temperature ( T c ) at about 68 °C. The large-scale and low-cost synthesis of VO 2 (M) are a challenge for materials scientists. In this paper, the influence of different additives on the synthesis of VO 2 polymorphs by a hydrothermal route was studied. F, Ti, Cr, Fe, Mo, Sn, Sb and W atoms can promote the formation of VO 2 (M), while Mg, Al, Co and Ni atoms are favorable for the synthesis of VO 2 (B), whereas, Na, Ca, Mn and Zn atoms have no influence on the formation of VO 2 (A). It was found that the T c of doped VO 2 (M) is very sensitive to the doped atoms. Some parameters, such as the temperature, reaction time, initial V 2 O 5 /oxalic acid molar ratio, tungstic acid concentration, were briefly discussed to give a systematic overview on the synthesis of W-doped VO 2 (M). In all cases, the morphologies of the doped VO 2 (M) show micro- and nano-rods structures. The T c of W-doped VO 2 (M) can be simply tuned by changing the doping concentration of W atom within appropriate limits. The variable-temperature infrared spectra show that the doped VO 2 (M) has outstanding thermochromic characters and optical switching properties. Furthermore, the enlarged-scale experiments for the synthesis of doped VO 2 (M) suggest that the same results can be acquired, which makes this route very suitable for practical application.