Synthesis and characterization of Mo-W co-doped VO2(R) nano-powders by the microwave-assisted hydrothermal method

Mo-W co-doped VO2(R) nano-powders were successfully synthesized by reducing V2O5 with oxalic acid via a microwave-assisted hydrothermal method. Pure nano-crystals of VO2(R) powders were obtained by adding a proper amount of urea as precipitant at a relatively low temperature (190 °C) and within a short time (3 days). Ammonium molybdate and ammonium tungstate were selected as dopants and their effect was also studied. The as-obtained products were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), differential scanning calorimetry (DSC) and X-ray photoelectron spectroscopy (XPS). Mo-W co-doped VO2-waterborne polyurethanes (WPU) was then fabricated with isophorone diisocyanate (IPDI), 2,2-bis(hydroxymethyl) propionic acid (DMPA) and nanosized Mo-W co-doped VO2-poly(ε-caprolactone) (PCL) as the starting materials. Organic-inorganic hybrid coatings are always achieved with adjustable contents of Mo-W co-doped VO2. The hybrid coatings with Mo-W co-doped VO2 loading on the glass substrate were characterized by variable-temperature UV-vis-IR transmittance spectroscopy and exhibited good optical properties and metal-insulator transition (MIT) properties in the infrared area. The results showed that the doping ions had little influence on the morphology of co-doped VO2(R), but they effectively reduced the phase transformation temperature (Tc). The Mo-W co-doped VO2(R) nano-powders showed prominent thermochromic properties with a low phase transformation temperature and highly visible light transmittance.