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

Abstract Mo–W co-doped VO 2 (R) nano-powders were successfully synthesized by reducing V 2 O 5 with oxalic acid via a microwave-assisted hydrothermal method. Pure nano-crystals of VO 2 (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 VO 2 -waterborne polyurethanes (WPU) was then fabricated with isophorone diisocyanate (IPDI), 2,2-bis(hydroxymethyl) propionic acid (DMPA) and nanosized Mo–W co-doped VO 2 -poly(e-caprolactone) (PCL) as the starting materials. Organic–inorganic hybrid coatings are always achieved with adjustable contents of Mo–W co-doped VO 2 . The hybrid coatings with Mo–W co-doped VO 2 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 VO 2 (R), but they effectively reduced the phase transformation temperature ( T c ). The Mo–W co-doped VO 2 (R) nano-powders showed prominent thermochromic properties with a low phase transformation temperature and highly visible light transmittance.