Simple Preparation of W-Doped VO2 Phase Transition Powder via APT

Vanadium dioxide (VO2) is widely applied in the fields of intelligent energy windows coating, optical switching devices, optical data storage medium, electrodes for electrochromic, lithium batteries and supercapacitors. VO2is a reversible first-order metal-insulator transition (MIT) at a critical temperature (Tc). VO2 is a monoclinic structure (M), and presents semiconductive and relatively infrared transparent below Tc, whereas it transforms into tetragonal structure (R), and presents metallic and infrared reflection above Tc. However, the high critical transition temperature of VO2 material (about 68 °C) limits its application.

To get over the drawbacks, a simple carbothermal reduction method has been presented by the simple direct mixture and calcination to prepare W-doped VO2 phase transition powder using the commercial vanadium pentoxide (V2O5) as the raw material, ammonium paratungstate (APT) as the doping resource. The preparation process of W-doped VO2 phase transition powder is prepared by carbothermal reduction method as following steps:

Commercial V2O5 (1–10 μm, purify >99%), APT (purify >99%), and carbon (C) powders (<1 μm, purify >99%) were used as received. Firstly, amounts of V2O5, APT, and C have been mixed by planetary milling with agate ball media for 6 h, in which the molar ratio of V2O5 to C for all samples was 2:1 and the molar ratios of V2O5 to 5(NH4)2O·12WO3·5H2O were shown in Table 1. Secondly, the mixture were poured into a quartz crucible, and then the quartz crucibles have been transferred into the vacuum furnace with N2 protective atmosphere. The V1-xWxO2(x = 0, 0.01, 0.02, 0.03, 0.04, and 0.05) solid solution powders have been obtained after annealing at 850 °C for 2 h.

The synthesized powders have been characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS), differential scanning calorimetry (DSC), and vibrating sample magnetometer (VSM), respectively. The function between phase transition temperature of VO2 and W-doping content and the phase transition mechanism have been presented.

To sum up, A simple carbothermal reduction method has been used to synthesize W-doped VO2 phase transition powder successfully using the commercial V2O5 as the raw material, APT as doping source, and C powders as reducing agent, respectively. the W-doped VO2 was a tetragonal structure. Tc of VO2 decreased gradually with increasing W-doping content by about 24 °C per W at%. Therefore, the carbothermal reduction method is a simple, high efficiency and low-cost approach to synthesize VO2.

• < Prev
• Next >