Yellow tungsten oxide is important inorganic electrochromic material, nowadays electrochromic device uses WO3 as raw material has been put into industrial production. Yellow tungsten oxide electrochromic thin film uses the electrochromic property of WO3, produced by physical vapor phase deposition, chemical vapor phase deposition and electro beam evaporation with low cost, well cyclic reversibility, optical property, fast color changing property. It can be applied in smart window, building window, rearview mirror and other field. Its color changing mechanism: WO3 (colorless) +xM+xe→Mx WO3（dark blue）
Yellow tungsten oxide electrochromism is related to its microstructure, it can be divided into three different groups according to its different method in absorbing power includes electrochromic material, thermalchromic material and photochromic material.
Radio refrequence magnetron sputtering produces ceramic target yellow tungsten oxide electrochromic thin film process:
1.Clean ITO first with deionized water, ethanol, acetone and ultrasound oscillation machine, each for 15 minutes.
2.Take out test block and blow it, put it into vacuum chamber for sputtering coating.
3.After substrate is placed in vacuum chamber, it was pumped to about 3×10-3 , then condensed to 2×10-6 for half an hour. The substrate is heated to the best temperature. Then introduce Ar gas to O2 atmosphere to deposit in different oxygen atmosphere, surface of target is sputtered to remove impurity and oxide layer, sputtering power is adjusted to 100W.