Thermochromic properties of W-doped VO2/ZnO nanocomposite films with flower structures

Based on the nanocomposite structure and doping modification, we have studied the preparation technology of high performance nanocomposite thin film and its characterization methods. The W-doped VO2/ZnO nanocomposite thin films are prepared successfully on SiO2 substrates by the three-step method. The structure and morphology of the W-doped VO2/ZnO/SiO2 films are analyzed by X-ray diffraction, X-ray photoelectron spectroscopy and scanning electron microscope. Results show that the films are mainly composed of VO2 and high valence cation W6+ replacing the V ion in the W-doped VO2/ZnO/SiO2 films. It is found that the flake nanocrystallines resemble a flower in shape, and its size and orientational growth are reduced. The thermochromic properties of W-doped VO2/ZnO films are measured and compared with the single-layer W-doped VO2 films on SiO2 substrates with the same thickness. The variation of infrared transmittance of the W-doped VO2/ZnO/SiO2 nanocomposite film is increased nearly two times, the phase transition temperature reduced approximately to 39 °C, and the width of the thermal hysteresis loop is about 6 °C. The W-doped VO2/ZnO/SiO2 nanocomposite film has a high infrared modulation ability, a lower phase transition temperature, and a narrower thermal hysteresis loop. Thus the potential application of this nanocomposite film is significantly improved.