Preparation and thermochromic properties of sol-gel-derived Zr-doped VO2 films

Vanadium dioxide (VO2) films were prepared on the glass substrates with a sol-gel process using polyvinyl pyrrolidone as a crosslinking agent. Zirconium ions were doped to decrease the phase transition temperature of VO2 films. X-ray diffraction, electrical resistance and optical transmittance spectra were measured to study the microstructure and thermochromic properties of Zr-doped VO2 films. The XRD peaks of Zr-doped VO2 shifted towards small angles as the amount of zirconium increased, indicating an enlargement of lattice constants, which can be attributed to the larger radius of Zr4 + ions. The phase transition temperature of VO2 film reduced with increasing Zr4 + doping amount. When the amount of Zr4 + increased up to 2 wt%, the critical temperature of phase transition decreased to 50 °C while the visible optical transmissivity almost remained the same.